Hi everybody,
I have a problem. Well, actually my 6128Plus has a problem.
I finally managed to score this machine on eBay at a worthwhile price, and - of course - it's dead. That's why it was £20.
First thing I did was plug it in and nothing happened. That turned out to be because the power switch had one of the wires come off.
Plugging this in, I found that it now did absolutely nothing, except at least now the power light came on. My first suspect was of course the RAM, and I began to desolder the first one and noticed it was very hot! In fact all four chips were getting much hotter than they should.
So, they all came out. I tested them in my Commodore C16 and sure enough each of the 4 4x64Kbit didn't work.
Putting in 4 nice new (tested) 41464, fired her up and... still nothing. Sometimes my TV displays a badly synced red screen, sometimes it's unable to sync (I'm using the correct 6128Plus kit from eBay to power and display).
I was wondering if anyone had any suggestions? Note I don't want this machine repaired, so sending it away isn't an option - I need to repair it myself, but obviously any help would be great to help my learning!
Thanks people! And a fantastic site this is, too.
Edit: I should point out that the data lines and lower address lines are all fluctuating more or less as I'd expect, and I'm testing with a Burnin' Rubber and a Robocop II cart.
Hi Spirantho,
it sounds like you have a good idea of what to do and also have the equipment to test the machine. So a few questions first:
1 - Is anything else getting hot? The ASIC?
2 - Have you checked that you have a clean clock signal (Pin 125 of the ASIC)
3 - Is the 5V supply to the ICs stable and at least 4.75V ?
4 - Have you tried connecting a speaker and seeing if holding the backspace / del gives a beep?
Bryce.
Thanks for the help!
Now I have the new RAM in, yes, the ASIC gets warm, but no more than I'd expect. The Z80 also gets warm. The RAM chips are vaguely warm but nowhere near as hot as the old ones.
My oscilloscope isn't fast enough to cope with the 40MHz crystal, but measuring with my multimeter, the voltage rises to 2.4V, so I'd guess it's ok. The clock on the CPU (pin 6) seems to be correct, anyway, so I don't think it's that.
The +5V line is running at +5.1V, and is smooth.
I'm currently running without the keyboard - but even so as I'm running with Burnin' Rubber, am I right in thinking it should be producing sound anyway, and the DEL button wouldn't have that effect. Nonetheless I just tried it and it still did nothing.
Well if you connect the keyboard and press F1 at startup it will be in basic and then it should make the beep. The reason for this is I wanted to find out whether it's just the display that's not working or something more. Pin 125 of the ASIC is a 4Mhz CLK output, not the 40Mhz input. If the 4Mhz is working, there's a good chance that the ASIC is ok.
The next thing you can check is the cartridge port, because if the cartridge isn't being read properly, then the machine isn't going to start anyway. Do a continuity check between each cartridge pin and some spot on the PCB that they should be connected to. If all connections are ok, then move on to the Graphics:
The ASIC has 4 digital outputs per colour. Red0 -> Red3 (pins 113 to 116), Green0 -> Green3 (pins 109 to 112) and Blue0 -> Blue3 (pins 104 to 107). You should be able to read a fluctuating digital signal on most of these pins (depending on what the screen is meant to be displaying). These 12 signals are going to the 40464 (IC115 triple DAC) and you should also be able to read the analogue RGB signals on pins 15 to 17 of IC115.
Let me know how it goes....
Bryce.
Do I not need a BASIC cart for BASIC? I'm using a Burnin' Rubber cart from my GX4000 at the moment.
Pin 125 appears to be oscillating correctly.... I really hope this means the ASIC is working because I can't change this chip!
I'll do the cartridge continuity presently, but looking at the pins, there's data flying around just fine, and if it were a bad connection, there should be a difference depending on which cart I put in, and there isn't (BR, Robocop II or no cartridge, same effect).
The 40464 has pins 2,3,4 with a low voltage with occasional spikes (multimeter reads at 0.3V). Pin 5 is set constantly high (+5V). All other video inputs are set very low, with no discernable spikes.
Thanks again for this, it's appreciated!
Edit: Something that may be interesting....
A0 thru A6 are all working correctly if the CPU is accessing its bus sequentially. Lines A7-A15 are always low. In other words, address $0000 to $007F are being used in order by the CPU, at which point it seems to return to $0000. The oscilloscope is showing A0 changing twice as fast as A1, which is twice as fast as A2, etc. etc., until you get to A6... which is exactly what you expect in a binary counter.
Oh, it's a red GX4000 cartridge :( I thought it came with the Plus and had Basic and Burning Rubber on it.
As far as the signals are concerned, if the ACID isn't making proper contact, there will be lots of data flying about, but the CPC still won't work properly. Check whether the SIN signal (Pin A3 of the cartridge socket) is switching at all (when a cartridge is connected).
The fact that only the Red pins 2,3,4,5 isn't a good sign though. This points back to the ASIC having problems and as you say, swapping this isn't an option.
Bryce.
(Did you see my edit above?)
Just checked A3 and it's going all over the place, which I'd guess is correct...?
Yeah, just read the edit. Strange. Maybe someone who knows the firmware routines better than I do could comment on this? What happens on startup at 7F? Is it expecting something it's not getting? Or is A7 shorted to ground somewhere which would reset the CPC everytime it sets A7 to "1" ?
Bryce.
If you're using a GX cartridge there is no firmware, it'd just launch straight into Burnin' Rubber (the firmware is stored in the Loco BASIC cart).
Ah, I was slightly wrong.
A0-A6 are all that are being used *after* the first half-second or so. Before that, A10 is accessed which is what I believe should happen.
Looking in WinAPE, there is a bootstrap code:
LD BC,#7F89
OUT (C), C
JP #0591
so A10 should pulse high right at initialisation (the 0591), and indeed it does. That means the CPU is executing the program more or less correctly. The weird thing is it then jumps off into no-man's land, and just cycles those 7 lines.
If the ROM isn't being read correctly, then maybe the data lines aren't being held, and are floating. This would explain the erratic behaviour, as the CPU would be doing random stuff. I wouldn't expect it to carry on though, I'd expect it to HALT when it reaches an undefined opcode. It's not executing NOPs because the data lines are all with data, albeit not as regular as the address lines.
Perhaps therefore the problem is that the ROM data isn't getting through to the CPU, but the bootstrap code (assuming WinAPE is accurate) is being executed.
The /ROMENABLE line is fluctuating, so that seems ok.... but it seems like it's just not being used.
Next bit of 'progress'....
I just tried with no cartridge in. The other address lines are cycling like A0-A6! This means that presumably it's just executing NOPs, which is fine. At least it means it's executing. The odd thing is the shape of the curve:
[attach=2]
Sometimes because my 'scope is a cheapish digital one, it can be misleading. But I'm wondering if the obvious disparity in amplitudes of the curve could have anything to do with it? This was A13 (I think - one of the higher A lines).
Here's a close-up of A11:
[attach=3]
So with no ROM, it's doing what we expect. With a ROM in, it's just getting junk. But it seems like the lines may be unstable at the best of times....?
I'd definitely clean all the cartridge socket contacts to be sure the problem isn't there. But the question I keep asking myself is: What killed all the RAMs? and what else might it have killed in the process. Unfortunately I come back with the answer I don't know, but it could easily have killed the ASIC in the process :(
The strange curve is interesting though, it doesn't look like it's really floating, but it's not good either. Are there any signs that any other parts might have been replaced during previous repair attempts? The "semi-floating" curve can occur if a pull-up resistor of the wrong value was used for example. With the machine turned off, you should measure the resistance between A13 and 5V and A13 and GND and compare it with A11 or another known good address line.
Bryce.
If it were a dirty contact, I'd expect at least some sporadic activity. I don't think it's that (and it all looks clean).
I measured the resistances but it's >2MOhm to both +5V and ground, so that doesn't tell me anything I'm afraid.
As for what killed the RAM - that's exactly what I want to know! It's really odd for all the RAM chips to go kablooie like that, and I'm keeping a very close eye on the replacement chips - but all seems well so far.
There's no signs of repair on the board - the only solder marks are those from myself - I changed the electrolytics to be sure of that, and I also socketed the RAM chips to replace them. Apart from that it's identical to normal.
I don't think there are any pull-up resistors on the address lines are there? There's some 33Ohm resistors on the RAM address lines but they all check out OK.
Very puzzling. How I wish I could just remove the ASIC and try it in a working machine!
Quote from: Spirantho on 16:39, 21 February 12
This would explain the erratic behaviour, as the CPU would be doing random stuff. I wouldn't expect it to carry on though, I'd expect it to HALT when it reaches an undefined opcode.
From the Z80's point of view there is no such thing as an undefined opcode. Every possible combination of bytes does
something even if that isn't normally a useful thing.
Good point.
What I really need is a homebrew cartridge with a space for an EPROM on. I can only burn up to 27C256 though, so there's probably no easy way is there? If I could do that I could write my own test ROM which would do what I tell it to immediately.
A quick thought - the most obvious problem with the machine is that the display doesn't sync. If there's anything on screen at all, it's all red with no hsync, and occasional lines of white. The display sometimes starts yellow.
Is it possible for a bad program to corrupt the display like this? Or should it always be static? In other words - can the ASIC be told to give a corrupt sync (i.e. switching quickly between screen modes or something)? If the CPU is executing NOPs, why is there no sync? Shouldn't the display just be constant?
Quote from: Spirantho on 17:50, 21 February 12
Good point.
What I really need is a homebrew cartridge with a space for an EPROM on. I can only burn up to 27C256 though, so there's probably no easy way is there? If I could do that I could write my own test ROM which would do what I tell it to immediately.
A quick thought - the most obvious problem with the machine is that the display doesn't sync. If there's anything on screen at all, it's all red with no hsync, and occasional lines of white. The display sometimes starts yellow.
Is it possible for a bad program to corrupt the display like this? Or should it always be static? In other words - can the ASIC be told to give a corrupt sync (i.e. switching quickly between screen modes or something)? If the CPU is executing NOPs, why is there no sync? Shouldn't the display just be constant?
without a cartridge installed you should see a coloured screen (purple or yellow or similar).
on the left side will be short black horizontal bars, spaced approx 4 scanlines apart. they will probably scroll up the screen.
what then should happen is that the asic and acid talk to each other and the cartridge is executed.
the display will probably look like this until the cartridge or basic/os program suitable values to the asic, a normal screen will then be shown, this may not be the correct colour, but should see a border.... if all is good it will be blue/yellow with text (if os).
if you *can* get burning rubber to work, and the cart is known good, then you can press r,t,g,5 to simulate joypad 2.
alternatively connect a joystick/pad if you have one for joypad 1.
if you're seeing junk when a cart is in, it's probably the acid causing trouble and giving the z80 garbage to execute. 7f/7e or similar.. perhaps b1/b0.
if the cart is in and the acid is working correctly in it, you should see other data..
can you test with another cart?
The sync signal is produced directly by the ASIC too. You should be able to measure this signal on pin 118 of the ASIC or direclty at the monitor port with your oscilloscope. If the ASIC isn't outputing anything on this pin, then it's definitely the ASIC that has died.
Bryce.
There definitely is *a* sync signal being produced, but the TV isn't syncing. It's almost like the VSYNC is valid but the HSYNC is wrong.
I think most sane people would probably write off this one, but - not being afflicted by "sanity" - I'm not giving up.
As luck would have it, there was this item on eBay:
http://www.ebay.co.uk/itm/250999218764 (http://www.ebay.co.uk/itm/250999218764)
Now £30 for three Burnin' Rubber carts, one GX4000 box, two joypads and two manuals isn't that bad on its own, but when you consider the two dead GX4000s it's a bargain, even if it's just for parts! I reckon the chances of the ASIC being dead in both of these AND my 6128 are fairly low, so it's worth a shot.
I also bought myself a little Aoyue 8208 SMT rework station (not just for this - I'm not that crazy!), so with a bit of luck and a following wind, I may just get lucky. I'm going to try and repair one or both GX4000s first, and then I can try switching the ASIC from the 6128 into a GX4000.
Of course please don't stop with the ideas in the meantime! If I can get away without switching ASICs I'd like to. :)
@arnoldemu
I've tried with two carts and no carts, and it's identical each time. My understanding is that with no ROM in, the display should still be steady, whereas I'm getting no sync.... so I know it's not the ACID. But thanks for the help anyway!
It looks like you know your stuff. I assume you know how difficult it is to swap one of these without damaging it, but I wish you luck.
The Sync signal coming from the ASIC is a csync signal so it should either have a good H and Vsync combined or nothing at all, so if you can record it on your osci, it's quite easy to see whether it's correct or not. Have you also checked that the signal is really making it to the monitor socket? And have you tested the SCART cable you're using on your good GX4000?
Bryce.
To be honest, I know my way around older machines well enough (I actually have a blog at mutantcaterpillar.wordpress.com but you may not like it because of the amount of Spectrums on it :) ), but I'm still learning about SMT. I've learned enough to know I need a reworking station though!
I've not really looked at the sync signal, though - there doesn't seem much point because even if the sync is completely up the spout then the audio will still play - and it doesn't. That means that although the CPU is executing stuff, it's not doing anything.
One thing that I noticed but didn't verify is that the RAM data lines may be held low (or high?) but I need to look into that more tomorrow. It's possible the RAM controller in the ASIC is kaput, so that'll be my next tests....
Although this site is 99% CPC, most of the guys here are general 8-bit fans (as long as you don't start praising the C64 :D ). Check out these threads: http://www.cpcwiki.eu/forum/other-retro/what-retro-hardware-do-you-have/ (http://www.cpcwiki.eu/forum/other-retro/what-retro-hardware-do-you-have/)
http://www.cpcwiki.eu/forum/other-retro/video-game-consoles-you-own-%28and-possibly-collect-games-for%29/ (http://www.cpcwiki.eu/forum/other-retro/video-game-consoles-you-own-%28and-possibly-collect-games-for%29/)
I dabble in everything from Acorn Electrons to ZX81s and everything 8 or 16 bit in between.... So I'm off to read your blog :)
Bryce.
Seriously good blog. I suspect we are actually siamese twins who were separated at birth. I've bookmarked the site and have reading material for at least a week :)
Here's one of my patients that might give you some reading pleasure until your two GX4000s arrive.
Bryce.
P.s. If you do this much hardware repair, you really need to invest in a better oscilloscope.
Thanks for the compliment!
If you ever need a ZXVid module (a little board I make that fits inside the ZX81 modulator case, but gives a properly compliant composite video signal so you can connect to modern TFT TVs) then let me know and I'll give you a discount as you've been so generous with your help!
I would list all the machines I have at home and at work but it'd take a while. :) In terms of Amstrads, though, I don't have much - just two CPC464s at work, a CPC6128 of my own at home, and the 6128+ at work. And of course my GX4000 at home.
I have a ZXVid - it was a godsend for one of my ZX81s that I couldn't get any other composite mod to work on.
Nice work & thanks for making them.
I think I read here about a test cartridge for the plus models, does someone have one?, or any more details about it?
Quote from: Spirantho on 21:26, 21 February 12
I'm still learning about SMT. I've learned enough to know I need a reworking station though!
I bought myself one of these http://www.ebay.co.uk/itm/260896529440 (http://www.ebay.co.uk/itm/260896529440) a couple of months ago. It's definitely a "budget" rework station, but it does the job remarkably well. The "automatic switching off when a magnet in the handle is detected by the stand" isn't very reliable, but that's not a massive problem. Dave Jones at EEVblog gave it good reviews.
Quote from: steve on 23:31, 21 February 12
I think I read here about a test cartridge for the plus models, does someone have one?, or any more details about it?
On here: http://www.winape.net/downloads.jsp (http://www.winape.net/downloads.jsp) at the bottom - Arnold Diagnostic cartridge. I put the link to the downloads page because there's other useful stuff there too...
Quote from: Spirantho on 21:07, 21 February 12
As luck would have it, there was this item on eBay:
http://www.ebay.co.uk/itm/250999218764 (http://www.ebay.co.uk/itm/250999218764)
Nice find. If you don't want all the Burnin Rubber Carts I'll buy one off you (being an opportunist, sorry).
Good luck with the 6128 plus!
Quote from: Spirantho on 22:36, 21 February 12
Thanks for the compliment!
If you ever need a ZXVid module (a little board I make that fits inside the ZX81 modulator case, but gives a properly compliant composite video signal so you can connect to modern TFT TVs) then let me know and I'll give you a discount as you've been so generous with your help!
I would list all the machines I have at home and at work but it'd take a while. :) In terms of Amstrads, though, I don't have much - just two CPC464s at work, a CPC6128 of my own at home, and the 6128+ at work. And of course my GX4000 at home.
Actually my ZX81 has the cheap and nasty BC337 / 100R Resistor to ULA pin 16 solution, which is far from compliant, but works perfectly on my TV. I don't know the ZXvid mod, I'm off to check that now...
I forgot the link to the "patient" reference above: http://www.cpcwiki.eu/forum/other-retro/anatomy-of-an-8-bit-over-voltage/msg26308/#msg26308 (http://www.cpcwiki.eu/forum/other-retro/anatomy-of-an-8-bit-over-voltage/msg26308/#msg26308)
Why do you have 464's and a 6128+ at work? I need to talk to my boss :D
Bryce.
Because I am the boss. I run a (very) small company which currently writes bespoke Android apps, but also has a growing sideline in retro computers (hence my shop, http://www.mutant-caterpillar.co.uk/shop/ (http://www.mutant-caterpillar.co.uk/shop/)).
Part of what I do is repair old machines - I'm the guy who fixes Spectrums for people mostly, but I've also done Atari STs, an Archimedes A3010, and other oddments. Hence it is my job to collect as much retro-related stuff as possible. I have my wife part-time working for me testing all the games I get in, while I fix up the hardware, and another fellow here is working on a completely seperate contract.
This 6128+, by the way, is (hopefully) going to be my "test rig". I have to have each bit of hardware so I can test software and the like, and "junkers" like this are just what I need - it's unsaleable because the disk drive is missing, but I can probably rig up a standard 3" drive in there (with a 12V cable connected to my CPC6128 modulator). That way I can repair other machines as they come in - not that I'm likely to see many other pluses! :)
Anyway, back on topic, and enough of me droning on. :)
There's something missing in this 6128+. It's ... er... kind of important.
It's the /NCAS0 line. It's flat. Flat as a pancake. The RAM chips are activated on the column strobe (CAS) which never comes, so the RAM does nothing. On my GX4000 the CAS0 line immediately kicks into life, but not on the 6128+. I've removed the RAM chips, still no signal on it. If the RAM is never being accessed, goodness knows what the 6845 core of the ASIC thinks it's doing, probably causing no sync.
So... I'm thinking after all that it is the ASIC.
I've asked the bloke with the GX4000s to send them first class instead of second. :)
@beaker:
Sure, give me a quid for postage and it's yours. They're not worth anything really and I'm guessing you don't want it for playing Burnin' Rubber so much as hacking apart for your own EPROM or something...?
Hmm, no /NCAS0 is not good and (unless R156 has been removed or shorted to ground) would suggest that the black square you are looking at is indeed an ex-ASIC. Just out of interest, is /NCAS1 doing anything?
Sounds like a nice little business you've started, there are many UK based users here that might like to make use of your services. But why bother with a Plus if you only want to test CPC software? As far as I know, all disc based CPC software will work on a standard 6128 too and with a simple lead, you can test CPC tapes too.
Btw. If you are looking for hard to find retro components, there are several people here with good sources, so just post a "I'm look for..." message. The user "Eliot" also has an online shop for CPC parts (no ASICs though).
Bryce.
Excellent, thanks for that tip. I'll take a look.
R156 is fine - I measured 33 Ohms between pin 93 of the ASIC and pin 16 of the 41464.
As for why I want a plus - partly because they're cool. For me, anyway. :) More seriously, though, I want to be prepared for any repair job that may come in.... and if I can learn how to repair Amstrad Pluses, maybe I can get more on the cheap and fix them up. This has the benefit of me being able to eat, and also the benefit of there being one more Plus in the world, which is a Good Thing (tm).
It also helps to have such weird machines as pluses in case I get a query from someone asking if a game I'm selling works on a plus, and that sort of thing. I know there are emulators, but there's nothing like the real thing, especially for testing!
Yeah, I find the Plus cooler too and it takes up less space on the desk. Unfortunately it belongs to the catagory of 8-bit where most of the functionality was done in a difficult to get custom chip, like the Acorn Electron and to a certain extent the ZXs with their ULA, which means many of them aren't repairable anyway. I've seen there's now an Altera based ULA replacement for the ZX81. Maybe we need to start looking at something similar for the Pluses ASIC?
Bryce.
P.s. Who "thinks" that they have trademarked "Good Thing" ?
http://boards.straightdope.com/sdmb/archive/index.php/t-211240.html (http://boards.straightdope.com/sdmb/archive/index.php/t-211240.html) is also a Good Thing (tm) :)
Spectrums are easily repairable. They were so common, you still get lots of erstwhile technicians stocks come up. Hence I have about 12 ULAs spare! And you can buy a tatty Speccy for a couple of quid anyway.
An ASIC replacement for the Plus would be very cool, but quite complicated. Any takers? :)
Quote from: Spirantho on 12:58, 22 February 12
http://boards.straightdope.com/sdmb/archive/index.php/t-211240.html (http://boards.straightdope.com/sdmb/archive/index.php/t-211240.html) is also a Good Thing (tm) :)
Who the fuck is Martha Stewart?
Quote from: Spirantho on 12:58, 22 February 12
Hence I have about 12 ULAs spare!
Yup, I hoard these type of parts too :)
Quote from: Spirantho on 12:58, 22 February 12
An ASIC replacement for the Plus would be very cool, but quite complicated. Any takers? :)
Not me! :)
Bryce.
http://en.wikipedia.org/wiki/Martha_Stewart (http://en.wikipedia.org/wiki/Martha_Stewart)
To be honest, though, I don't know, I just know the name. It was something around many years ago at the dawn of time/the internet, though, when companies were trying to trademark everything, so it just became a self-effacing dig at corporate bods.
Personally, I just do it for the heck of it. :)
Drat! Dead ASIC! Few words are as disappointing to a Plus/GX4000 owner! I've been watching this post with some interest as I had my eye on not only the 6128 Plus auction, but also the GX4000's. I actually logged into ebay to buy them after sleeping through the day after being on nightshift and found they had been bought, I wondered who else in the world but me would want two dead GX4000's!??
I guessed that the Plus may be a victim of a dead ASIC as I could see the power switch interlock was missing suggesting the cartridge might have been pulled out with the system powered up.
As for the GX4000's you won, it would be worth checking the Z80, I had picked up a dead GX4000 recently and was greeted with a black screen when I powered it up, just for the sake of daftness I swapped the CPU for a known working one I had lying around, and unbelievably it booted straight up. I'm using it for the final version (read neat and tidy version ;D ) of the GX4000 to a CPC Plus modification I'm working on. Just wish I could get the disk interface working properly!
If you do manage to find a working ASIC and repair the Plus, please document it so we can see how it was done!
Good Luck!
Whoops, sorry about that. :) For what it's worth they should be very handy! And yes, the Z80 will be the first thing to check as it's simplest, followed by the RAM as they're most likely to be gone.
What were you after two dead GX4000s for? Maybe I can help somehow once I've finished with them.
Incidentally, the power switch is just fine, it was just a bit loose.... you'd have to try pretty hard to take a cart out while it was on! Plus I don't think that would have blown all 4 RAM chips, that smacks more of a major power surge or wrong polarity PSU or something.
For what it's worth, the 6128 case is actually quite good - the biggest problem is that posts to hold the drive seem to be broken, and of course there's no drive - finding a 3" drive that doesn't need 12V is going to be ... entertaining. I've not looked on this site yet, though... First thing is to see if I can get the thing booting up.
Needless to say I've been taking photos for my blog, so if all goes well you can expect it to be up there soon!
Even if I can't get it working, there's nothing quite like a properly dead machine to teach you about how they work. Without this machine I had no idea about the innards of the pluses, and now I know much more about the ASIC, the ACID, the 6845 emulation, the 5V only floppy drive, all that gubbins. Dead machines are great, even if you never get them working. :)
To be honest, I was hoping that there would be a good chance that one of them at least could be a quick fix, if that failed then the RAM ICs are always useful to have around as long as they didn't get blixed in the event that killed the console and Z80s are useful to have for future repairs. And its always good to have a junk PCB to check how things are connected should the need arise. As you say, you can learn a lot from a dead machine!
As for what kills these machines (the Gx4000s) I think that its likely due to the 11v power supply being pressed into the 5v socket if its not the cart being ripped out. I know it doesn't fit but it can make enough of a contact to send those volts where they don't belong. I have occasionally made the same mistake when working on or setting up my main GX4000 console. Usually if it happens the console is ok after a power cycle or two, but sometimes is unresponsive, and will not power up even after disconnecting and power cycling several times. Then it just magically comes back to life again after a few minutes. Needless to say I've gotten a lot better at remembering where the PSU needs to be connected!
I suppose an incorrect polarity PSU connected for a while would probably result in a very dead machine so is very probably, as you say the most likely scenario that lead to your machines unfortunate demise. :'( I guess the switch was a red herring. On the bright side you at least have the hard to find FDC IC and the SED Data Separator in the 6128, assuming they are ok, if you find a 464 plus you can upgrade that to have disk capability!
Exactly! Parts are always useful to have! Not least the case - if I can find a beat up 6128+ in future I can do a switch, as this one is fine apart from being dirty.
If you ever need any Z80s, let me know, I have loads. I buy them about 10 at a time from the Netherlands - there's an eBay seller there who does them for about £1.50 or so each, but postage is higher of course - but if you buy 10 at a time it's not a problem.
I noticed last night the braindeadness of the power supplies. It's almost as braindead as the Sinclair ZX80, which has the power connector at the back of the machine (where you can't see it) right next to the identical cassette lead sockets (where you can't see them). Real masterstroke, there, Clive!
The asic,is very expensive:
http://www.donberg.ie/search?query=40489 (http://www.donberg.ie/search?query=40489)
I think is best search another cpc + :(.
That price is bonkers. Given I just paid half that for two entire GX4000 consoles, it'd be a bit crazy to pay that much. Admittedly those consoles are non-working but chances are one of the ASICs is good, and even if not it was worth it in ancillaries.... and there's no guarantee that ASIC on that site is working either, unless it's used, in which case you may as well just buy a GX4000 for half the price.
It's kind of like Commodore 64s. You can either buy a SID chip for £25 or an entire C64 (with a socketed SID) for a fiver. Crazy.
Apparently my GX4000s were posted today, but they went second class. I'm hoping they arrive by Friday!
@Badstarr: Despite it being one of the longest living urban myths, pulling a cartridge out while the machine is running is very unlikely (almost impossible) to damage anything inside the CPC.
@Spirantho: If you're clever, you'll make a small circuit to bring the 5V up to 12V for a standard 3in drive ;) the ZX Spectrum does this too (hint, hint).
@Dragon: I wouldn't believe all that you read on Dönberg, they offer quite a lot of stuff that they don't actually possess.
Bryce.
@Dragon; That does seem pricey, however, I'm amazed that one is even available. I think if the suppliers knew the rarity of such an item, its price would climb to ridiculous proportions. The fact is that they are unlikely to sell it unless an enthusiast is in need of one. If I had a broken plus and I knew that a new ASIC would fix it for sure, I would pay €65 rather than wait to pay more for another machine. As long as I was reasonably sure it wouldn't be needing a new ASIC for a fair while!
On the other hand, I would also be quite suspicious that the part might have been removed from a PCB by some poor kid, on a bonfire in a landfill site in a thirdworld country.
The company is a sourcing company, not a supplier, they don't actually have one, they just (believe) they know where they can get one.
Bryce.
Quote from: Spirantho on 11:38, 22 February 12
Sure, give me a quid for postage and it's yours. They're not worth anything really and I'm guessing you don't want it for playing Burnin' Rubber so much as hacking apart for your own EPROM or something...?
Fantastic thanks! Yup, you read my mind, I bought an EPROM programmer, EPROMs and a socket a few months back ;D Also Bryce put a DIY project on this site recently to mount the ACID chip inside the Plus which I fancied having a go at at some point. I'll PM you to get details of where to send the money.
A picture speaks a thousand words. :)
[attach=2]
It would appear that the Aoyue 8208 does, in fact, rock. Especially for £60.
Nice job!
That's the easy part though, soldering the replacement ASIC on won't be as much fun :laugh:
Looking forward to seeing the end result. If you clean the solder pads sufficiently then soldering the new one on shouldn't be that difficult.
Bryce.
Just googled the Aoyue 8208. Looks like I should have bought that instead of the Chinese one I actually got. It's about 50% more expensive but I'd say probably worth twice the price...
Although an SMD rework station is a handy thing to have, it usually gets used a lot less than the soldering iron. So I wouldn't spend too much on one. I would recommend spending a few hundred euro to ensure you have a good branded soldering station such as Weller / Ersa, because you need to be sure that the tips which (should) get changed regularly are still available in a few years, but an SMD rework station is just a glorified hairdrier and shouldn't cost more than €100 unless you really do use it daily.
Bryce.
I should really get one of those SMD rework things! Mind you I've removed a fair few ICs without any damage using my cheapo heat gun, that's how I made my BASIC/Burnin Rubber cartridge. I wouldn't want to risk it on a precious ASIC though. I have often wondered how precise ASIC emulation is on various software emulators and whether or not that emulation could be pushed into a FPGA that could be physically soldered in place of an ASIC. A rather expensive solution I know! But pluses are so damned rare and expensive and I would guess that all the ASICs that were manufactured went directly into a machine without a second manufacturing run being produced when it became apparent the Plus and GX4000 machines didn't have legs commercially. I could imagine the conversation between Lord Sugar and who ever was in charge of the Plus manufacturing went something along the lines of "So these new computers with the expensive custom chip we designed aren't selling well then?... Well I aint throwing any more money at it... and for that reason... YOU'RE FIRED!"
Yes, but unlike an electronic hobbiest, large companies usually sign off supply contracts before they've sold the first unit, so depending on what their marketing people were saying, they might have signed a deal to take a few thousand ASICs per month for a set amaount of time, so even if they not selling the projected amount of units, the parts are still arriving. That's the only way you can get the component prices down to the level you want/need. The questions remain: Where were they being delivered to? How much stock piled up after the production was ramped down? And what happened to the parts afterwards?
Having worked in this industry, I could imagine, that (if they weren't subsequently dumped), there could easily be 10's or even 100's of thousands ASICs stored somewhere.
Bryce.
Quote from: Bryce on 10:29, 24 February 12
I would recommend spending a few hundred euro to ensure you have a good branded soldering station such as Weller / Ersa, because you need to be sure that the tips which (should) get changed regularly are still available in a few years
Bryce.
So time to throw out the Antex soldering iron that I borrowed from work 7 odd years ago and forgot to return if I want to do the ACID inside mod?
QuoteHow much stock piled up after the production was ramped down? And what happened to the parts afterwards?Having worked in this industry, I could imagine, that (if they weren't subsequently dumped), there could easily be 10's or even 100's of thousands ASICs stored somewhere.
1,is in usa.(Is the domberg sell).
These are the component survivors of amstrad:
http://www.netcomponents.com/es/results.htm?r=1&t=f&src=&so=&lgc=begins&d=1&pn1=amstrad&slgc1=begins (http://www.netcomponents.com/es/results.htm?r=1&t=f&src=&so=&lgc=begins&d=1&pn1=amstrad&slgc1=begins)[size=78%] majoritary,older gate arrays.+400 acids chips.[/size]
From,uk,france,netherlands,depend the source.
@beaker: If it's one of those small yellow non-regulated ones, then I would only use it to solder wires, not components. If you seriously intend soldering an ACID, then I would only recommend a regulated iron, where you know exactly how hot it is.
I've gone around in circles with these types of companies in the past trying to get rare parts. - Supplier A says he has a source in the US, but that's also a re-supplier who thinks he can get the part in Korea, but that's also a re-supplier who thinks he can get one from the original Supplier A. Also, there are several re-suppliers who scan lists (which are way out of date) from other suppliers or that automatically generate lists of all known parts and claim they have them in stock. So I gave up using these "services" years ago.
Bryce.
I went round in circles trying to order an FDC with these sorts of companies. Just as Bryce said they tend to cross link themselves to the point where each "supplier" is referencing the other as a stockist. I was trying to get an exact replacement, right down to the last id digit. In the end I took a chance on a couple of FDC's on ebay that matched up when I looked at the data sheets and I confirmed they worked ok by installing them in my Plus machine. Even the SED data separator was labelled as an 'A' rather than 'AC' and that too works fine. Like I've said before, I'm no expert on IC code numbers so I suppose that as long as the main ID is correct anything that follows may not be that relevant in terms of spec.
Actually, a quick question, without the intention to hijack the thread, as you can see in the picture posted by Spirantho, there is a variable resistor near the RGB connector, does anyone know what this should be set to? I just want to check that mine has not been disturbed at any point during its lifetime. Spirantho, if you could check for me while you have the bonnet up, so to speak, I would be very grateful! ;D
If you ever need parts like the FDC or whatever, then post a request here, usually someone (like me) will have a few spares. The second suffix on an IC number rarely signifies a functional change, so Type A can be considered equal to Type AC.
The Mini-Potentiometer beside the Monitor output is VR101 which is used to set the peak value of the Luminance. If you use a green monitor, then you can tweak the brightness of the display slightly by turning this. If you use a colour monitor, RGB, SCART, S-Video or whatever, then it really doesn't matter where this is set to, because you're not using the signal anyway.
Bryce.
Briliant! Thanks Bryce! ;D
A little upate...
I received the broken GX4000s today and sure enough, they're broken. In fact, both of them had two dead RAM chips. I mean, seriously, what is it with Plus machines and their RAM chips?!?
Anyway, having replaced them, I now get two almost working machines. One of them shows no RGB/Audio, but if you tune it in you can see the image and there's sound there too - Burnin' Rubber is working. The other one also has no RGB/Audio, but again there's a TV picture - quite a bit stronger, this time - but missing colours and still rather weak - but again, it runs BR.
I lifted the ASIC from the stronger of the two machines, and I've put it into my 6128. At the moment, though, there's still some pins not quite touching the pads, so I probably need to touch them up slightly. There's no signs of life on the 6128, but the RAM is now getting a CAS signal.
My question is this: Could the weak TV signal be a fault of the ASIC? I assumed not as the game was running visibly, including a (weak) sync to go with the (weak) graphics. What should I look at to correct the picture, if I need to? On the GX4000 there's a TV modulator, but there isn't on the 6128.....
The GX4000 produces the RGB picture exactly like the 6128 does ie: ASIC produces 3x 4bit colour signals and sends them to the 3x 4bit DAC to make analogue RGB and these can be measured as mentioned earlier. However, the GX4000 also sends these (and the Audio Signal) to a CXA1145 Encoder to produce the SCART and TV signal. If the CXA is blown it may be causing problems there. But the CXA also drives the UM1234 Modulator, so if this was dead, you wouldn't get a UHF signal either.
Eitherway, No the ASIC can't be to blame for a weak picture signal.
The variance in picture strength might be due to some idiot having tried playing with the modulator settings. As you are accustomed with Speccy repairs you'll know how sensitive the Speccys UM1233 can be, well the GX4000 uses the UM1234 which was no better :D
Does the SCART work? When you say RGB not working, are you referring to the monitor Socket RGB or the SCART RGB (They are two totally different signals).
'Bryce.
Interesting. I was talking about the monitor port. Not tried the SCART one..... need to do that....
Strange, the RGB and sync signals to the monitor connector are the same signals used to create both the TV UHF and SCART pictures, so if the TV works, then the RGB and sync must be present at the monitor socket. Are you sure your monitor works? :D
Bryce.
Yes, I'm sure. :) It works with my working GX4000 anyway...
Then check the RGB signals on pins 15,16 and 17 of the DAC (AMS48464). They must be there, otherwise you wouldn't be getting a TV signal and confirm that the same signal is getting to the monitor socket. Then check that your ASIC is sending an NSYNC signal and that this is also making it to the socket (it goes through a 220R resistor, so expect a voltage drop).
One reason for the dodgy DRAM in the CPC+ might be the fact that the Plus actually uses two different Ground plains. The DRAM had it's own ground plain that (extremely strange decision) was also used by the video circuitry. A spike on this plain could be the reason for the deceased DRAM and might also explain why something on the video circuitry is also not doing what it should.
Btw, If you examine the Plus schematics closely you'll find several other forehead-slapping decisions that no sane designer could ever justify.
Bryce.
Quote from: Bryce on 16:25, 24 February 12
Btw, If you examine the Plus schematics closely you'll find several other forehead-slapping decisions that no sane designer could ever justify.
Bryce.
Go on, Bryce. Spill the beans!
Quote from: CanonMan on 17:09, 24 February 12
Go on, Bryce. Spill the beans!
Seconded! I'd like to hear about them as well!
Quote from: Bryce on 16:25, 24 February 12
Btw, If you examine the Plus schematics closely you'll find several other forehead-slapping decisions that no sane designer could ever justify.
Bryce.
Sanity has very little to do with it indeed .. but i bet some of it is cost-effective :)
Check this video at 04:00-ish:
Sir Alan Sugar P2 (http://www.youtube.com/watch?v=ZlkTMmXpiJM#)
"Why is it there? Why?", lol.
Later he also tells about his great idea of squeezing everything into one.
I've noticed on one of my GX4000s that the monitor connection puts out a week signal. Its washed out and rather grey, I assumed that this could have been perhaps due to the monitor socket being active when you connect the 5v psu. It was just a hunch really, if the monitor output is live all the time then its certainly a bit weird that this happens. ???
As for getting the consoles going, well done! I think I may have some more as yet non investigated GX4000 boards knocking around that I might have try through the modulator, however, the majority of the ones I have got I have pulled the RAM ICs and they were working fine so I guess that wont fix them.
What I would say though, is that every time I connect my project GX4000 to its PSU, the TV senses it switches automatically to SCART. On the dead ones I've tried this does not happen. I began to wonder if the SCART pin 16 (blanking signal) might have lost its feed so the tv receives no sync? So no on screen activity makes the console appear dead? However, I would assume that the audio would still come through?
I really hope you manage to resurrect the 6128! I think it would be the first time its ever happened, but feel free to correct me if I'm wrong!
Quote from: Badstarr on 19:36, 24 February 12
What I would say though, is that every time I connect my project GX4000 to its PSU, the TV senses it switches automatically to SCART. On the dead ones I've tried this does not happen.
Sadly (and this is one of the very questionable decisions on the GX4000), the 10V signal is responsible for the Automatic switching of the TV, so that must be dis-connected or broken on the broken GXs. It would have been so easy to solve this without an extra supply / connector etc, but that was the Amstrad solution??
I'm not going to go through all the strange decisions, but... Unnecessary pull-up resistors and capacitors, non-optimised boolean solutions and the CPC could also be modified to require quite a bit less current without changing a single IC. And if they really wanted to make a low-cost computer, then they PCB could have been half the size (ok, admittedly they did do this on later versions).
Bryce.
Perhaps the weird design decisions are the result of having a team of radio engineers produce the CPC range. I read somewhere recently that this was the case. I do remember when I found my first, and none working GX4000, thinking that it was a crazy idea to have a twin PSU solution. I figured that the previous owner must have attached the 11v PSU to the 5v line. After opening the machine up and seeing that ASIC, I decided that a repair was probably beyond my knowledge and eventually threw the machine away. This was back in days when we had no CPCWiki and very little info on the WWW about the GX4000s. I really wish I hadn't gotten rid of it now, as I left all the ICs in place which is tragic really as I would have found some of them useful these days! I would think that between all the broken GX4000s I have found over the last year or so I could cobble together a working machine. Thats a project for another day I guess.
Quote from: Badstarr on 06:36, 25 February 12
Perhaps the weird design decisions are the result of having a team of radio engineers produce the CPC range.
Where did you get that from?
The original CPC certainly wasn't designed by radio engineers, Mark Eric Jones and Roger Hurrey had both worked for a company that designed very expensive word-processor computers.
I'm fairly certain that MEJ and his team designed the plus range as well.
It's all in "The Amstrad Story" by David Thomas. A very good book, IMO.
I think that was exactly one of the problems. The designers were accustomed to building expensive highend hardware and had no idea how to build low cost hardware.
As far as radio engineers are concerned, I think this was the case with Spectrum, but not with Amstrad.
Bryce.
I think they did a pretty good job, given that they only had about eight months to do it in!
just a question...
What happens if you connect a GX4000 on both a PLUS monitor and a TV... or perhaps a scart/peritel video recorder ?
or both on a monitor and a TV ?
concerning the "replacement" of an ASIC...
Would it be easier to use a socket ?
Also, is it possible to properly Retro engineer it ?
GX4000 connected to a monitor AND TV or SCART: Shouldn't be a problem because the CXA would still drive the TV SCART signal and the monitor signal would also be strong enough, so both should work in parallel.
ASIC Socket: The socket for this IC has a different footpirint, so it would be very difficult to solder the socket to the PCB.
Retro engineering: The function of the ASIC has already been simulated in emulators, so the function is known, converting this function to an FPGA or CPLD is not difficult, just a lot of work.
Bryce.
QuoteGX4000 connected to a monitor AND TV or SCART: Shouldn't be a problem because the CXA would still drive the TV SCART signal and the monitor signal would also be strong enough, so both should work in parallel.
So it can be easy to get direct/real video recording from a GX4000...
Do you mean - Watch one record the other? If so, yes.
Bryce.
Most video for amstrad stuff are either Cam Recorded from a real monitor or emulated...
Perhaps a moded GX4000 (like one turned into a proper 664PLUS...) would be a good longplay recording station...
This may be interesting and give a true Hardware experience.
Has anyone tried this ?
(Also sorry to spoil the topic.)
If I may briefly go back on topic.... :P
[attach=2]
I got an actual sign of life from my 6128+!
OK, it's not exactly the Burnin' Rubber screen I'm hoping for... but it's something.
This is the third ASIC in this machine - I think the second one works but I took it out because the pins were a bit misaligned so I thought I may want to come back to it later when I've had more experience with SMT stuff.
The screen above only happens with a cartridge inserted! This is good news, as it implies the ACID chip is talking to the ASIC. If I run it with no cartridge, I get the "No Signal" display I always got before.
The problem I'm having now is that after having had an ASIC soldered to it 5 times now, some of the PCB tracks are dry and the solder won't stick to them. I've connected the CPU clock line CLK4 via a wire - I'll probably do something similar with the rest, so it may get a bit cluttered!
Right now though, I have a motherboard with a working display, a working CPU, working RAM, and a working ASIC that just needs 10 connections soldering up somehow.
Phew.
I'm going to take a break for a bit now. Too much looking through a magnifier.... soldering SMT is tricky!
Getting close :) I'm sure it's just a dodgy connection on the ASIC at this stage. Yeah, SMD soldering is hard on the nerves :D
@MacDeath: It's also possible to do this with a CPC that has my S-Video adapter connected (effectively the same thing as the CXA1455 does in the GX4000). As far as I know, Markus has already experimented with recording things this way.
Bryce.
Just a basic stuff : have you verified all components and connectics ?
ok, this can be boring, long and delicate...
But a faulty condensator may be trickier too.
The only thing I can think of from my experiences with soldering ASICs is that you should check ASIC pins 127 and 129 (RAMDISABLE/ROMENABLE) for any cross connections from adjacent pins. I had some similar on screen behaviour when there was a slight short on one of these pins. There should also be a 2.2k pull down resistor on each pin. Just out of interest which number pins are currently not connected from the ASIC?
It's great to see some signs of life from the machine! It's getting there! ;D
I AM THE LIZARD KING!!!
Or something.
You won't believe this but....
[attach=2]
Here's the board:
[attach=3]
I noticed that most of the pins at the top right of the IC aren't used except by the printer buffer - which I'm not going to use anyway. All that was left there was the RAMDISABLE/ROMENABLE lines, the CURSOR and the Light Pen. Now I don't care about the Light Pen, and I don't need the CURSOR line for now. That's why there's two wires around the ASIC at the top right - they're pin 127 and 129 lifted (VERY carefully) and wired up directly as the solder pads are too dry now for the solder to stick.
Thank you to everyone who's helped me resurrect this very dead machine! I reckon I can still use the ASIC I took out of the other GX4000 - it should work, it's just a few pins need a touch of straightening. Is it of use to anyone?
Do I get a badge now for doing an ASIC transplant?
Nice work ;D
You have far more patience than I have :laugh:
I still have a few bits and pieces to do - I think some of the keyboard lines may be dodgy but I'm not sure as I don't have a BASIC cartridge. Also it crashes every now and again and the ASIC needs pushing down again - there's ONE bad connection to the CPU I think! Plus there's a dodgy connection on the video output line so it loses colour sometimes.
But overall, it's working and I'm well chuffed. Not only that but it's my first bit of SMT QFP removal/refitting, so it opens the door to all sorts of new repairs!
Yay! :)
Whoo! Hoo! Excellent work! I'm actually quite glad you beat me in those auctions! ;D So was my suspicion about the ASIC pins 129 and 127 any use? Or had you already got it working by the time I'd posted? I only ask as I would be rather proud of myself if my CPC ASIC skillz are actually becoming useful! lol! ;)
It was of use indirectly - I wasn't going to have a crack at the Plus today, but when I read your post - knowing that those pins weren't connected - I thought I'd give it a go!
You were dead right in your diagnosis though, so well done!
Thanks very much! ;D I now feel much more useful after a day spent trying to weld my car back together! I've never welded before by the way :o I have to admit, I much prefer soldering! As for CPC land I have just received a rather broken 6128 (vanilla flavour) that I will be repairing hope that it goes as well as your repair! I can see where the cause of death originated, the previous owner soldered a 12v PC power supply into it and a trace on the PCB lifted shorting +12v to a NAND GATE IC, I'll wager this will be an easier fix than an ASIC transplant!
Congratulations Spirantho a fine job, you have every right to by "well chuffed". It's also a good example why you shouldn't throw away broken CPCs, they can be fixed or at least used for parts to fix another one.
Bryce.
Exactly - never throw out anything like that.....
... which explains the amount of useless stuff I have scattered around. :) Never know when it'll come in handy!
Absolutely fantastic job, makes my current repair adventures of a 6128 (originial) and Acorn Electron look trivial by comparison!
I have looked into SMT soldering before done a few small things like resistors very difficult - I can't even begin to imagine how you did the ASIC not to mention removing one from another machine first!
Check out this video I got curious and did a YouTube search some very good tips on SMT soldering here though I don't think I'll be attempting any large chips anytime soon!
http://www.youtube.com/watch?v=3NN7UGWYmBY
Thanks for that video, it's great! Not seen it before.
Removal of SMT chips is actually very easy - you just need a desoldering station (mine cost about £40 and works brilliantly, it's an Aoyue 8208). It's the re-soldering that's difficult!
No problem! Yeah I thought the video looked great and just gives some really nice tips on how to do this more easily. I don't currently have a desoldering station but having looked at them I can see immediately how tos can make the work of removing the chips much easier!
I can imagine that soldering them back on os a real nightmare made even worse when multiple removals and reattachments begin to damage the solder pads. In the factory of course attaching the chip happens in seconds with a special machine if only we could get those at home!
How is the machine, still working...?
Trust me, get a desoldering station. It's not only useful on SMT chips - I usually use a desolder pump on through-hole, but occasionally you get PCBs that just disintegrate when you touch them with an iron (my bootleg Green Beret arcade board being a good example). Desolder pump (even with a temperature controlled iron) causes damaged tracks because of the low quality PCB, using my desoldering station I removed about 5 chips without a single damaged track.
As for the 6128, it's... well, it's working except I removed the ASIC again. :) There was still some dodginess probably caused by the mis-shapen pins on the ASICs I was fitting, so I've bought another dead GX4000 (on its way) and this time now I've had more practice, I'm hoping to get a better fix. Especially now I've seen that video! I've ordered some flux and paste flux specially, as well as a 10x loupe. :)
I could probably get the two ASICs I have back on it too but I want to get a really good fix on it, and that's safest with a new or cleanly removed chip (and as I've had more practice with the Aoyue now, I should be able to get a much cleaner removal). I'll put the other two ASICs back in the GX4000s - it doesn't matter so much if they're not perfect as GX4000s are so cheap - probably cheaper than the ASIC inside them!
You might like this video too:
http://www.youtube.com/watch?v=MqivHi7Qjvk
it shows how to use solder paste and a desoldering station to attach an SMT ic easily and gives a very nice finish! Could be useful for your ASIC transplant!
That does look pretty cool. I wonder how well it would work on such a big chip as the ASIC, though. Maybe I'll try it on my GX4000 boards to practice!
Off I go to eBay once more... :)
Yeah I was thinking the same and was surprised how they just spread the paste across all of the contacts but it does seem to sort itself out! The desoldering station sounds like an excellent investment, I think I'll chase one of those down next month (unfortunately I have reached my quota for tools this month). It explains how you're able to remove ICs so quickly - with a desoldering gun it's a lot slower and as you say tracks often get lifted, caused usually in my experience by solder being left on the other side of the leg i.e topside which then pulls a track from the top of the board when you remove the ic! Fortunately theres nothing that can't be fixed but wire links look ugly (you should see the back of the 6128 I'm repairing previous owner butchered the ROM sockets so I have four wire bypasses to link it all back up to the address bus - not pretty!
Solder paste is really good for large ICs like the ASIC, but it's expensive if you only solder on rare occasions. The paste has a shelf life of a only a few months, so it should be bought in very small quantities, just for the job you intend doing. Watching it "melt" under the microscope is really cool :)
Bryce.
Hehe.. I intend to find out. I just bought 10cc (which is funny, as I was listening to 10cc yesterday) of the stuff. Maybe I can try a comparison by doing one ASIC with the paste, and one with flux+solder....
light pen is used by light gun.. 2 games support this, so it's no great loss.
cursor is used by nothing in the cpc?
it's not displayed on the screen and I don't know of any hardware or software that actually uses it.
So don't worry about that either.
Quote from: Bryce on 12:53, 24 June 12
Watching it "melt" under the microscope is really cool :)
Bryce.
You got a microscope in your room as well? Wtf, does it sit next to the centrifuge? :D
Yes, you need a microscope to check SMD solder joints on accassions. You can see it in the picture here beside the oscilloscopes: Interview Bryce - NoRecess {the Amstrad CPC website} (http://www.norecess.net/interview-bryce.html)
My Centrifuge is in the Garage of course! Beside the particle accellerator :)
Bryce.
Great interview, really interesting - thanks for posting the link and enlightening to see the kit you're using! I don't have all of those tools but I certainly have enough to do most of the day to day repair tasks and will grow my toolset over time!
I'm totally with you that you have to be very careful not to allow a hobby to take up too much of your time. I often find myself in danger of getting obsessed when I'm desparately trying to get something to work and it is very important to make sure you spend enough time with the others in you life. I can imagine that having kids recently has totally changed everything. I don't have any yet but they're definitely on the horizon which i think will be a big life changer - but a very worthwhile one!
I've found SMD work using my hot air station pretty easy, although when I first used it I did have the blower on too fast and my tiny 0805 resistors blew away!
That said, 0.5mm pitch is tricky. Even with the tiniest syringe I could find (I think it's 0.2mm) it's really hard work getting the paste out thin enough that I don't end up with bridges between the pins. I do have a load of flux in a syringe I bought by mistake (also with no presser!), so i might try mixing that with my solder paste to make it a bit runnier which should allow me to apply the paste more fluidly.
Yeah the more videos I've watched using hot air guns the more I have been convinced that it is absolutely the right way to go - if I can heat up an IC then just remove it with tweezers when the solder melts it can be removed really easily and with no damage to the board!
What have you guys used in the past to suck the solder that inevitably is left in the holes occupied by the chip? I see you can get vacuum units to compliment the hot air blower - is that the way to go...? If so any recommendations?
Quote from: Bryce on 08:39, 25 June 12
Interview Bryce - NoRecess {the Amstrad CPC website} (http://www.norecess.net/interview-bryce.html)
Bryce.
Quotes below are from the interesting Interview Bryce - NoRecess {the Amstrad CPC website} (http://www.norecess.net/interview-bryce.html)
"I also did freelance design for several companies that made CPC and Spectrum hardware, which is where my 8-bit design really started."
What CPC hardware ( I asume addons?) did you design at the time and for what companies?
"I have actually developed more hardware for the XL/XE, C64 and Spectrum than for the CPC."
How did this happen?
"Other ideas on my list are: ...and a hardware diagnositcs card. "
One for the many dead GX4000s would be great :)
@Dame1701: I use desoldering wick most of the time, I find it works better than those pumps, especially if you need to get a very smooth surface to put a new SMD part on the pads.
@ivarf: Yes, I was designing stuff while I was in University for a small electronics company that did out-sourced design for several other companies. Some of the things were end-customer add-ons, but other devices were used to develop other hardware/software like porting data from one 8-bit to another, or to digitise sound / pictures that I believe were being used by a games company. I know that one of the devices was for DKTronics and I think some was for Code Masters, but I was never officially told who the customer was, I was just the student bum who had to do the design :D
I owned an 800XL and a friend owned a C64, that's why I started developing stuff for them first. I only really started doing CPC stuff when I joined the Wiki (around 2009). So the CPC stuff hasn't caught up with the other 8-bitters yet.
The diagnostic card is still just an idea. There's a few other things I'd like to release before then. But any and all ideas are always welcome.
Bryce.
Quote from: Dame1701 on 18:23, 25 June 12
What have you guys used in the past to suck the solder that inevitably is left in the holes occupied by the chip? I see you can get vacuum units to compliment the hot air blower - is that the way to go...? If so any recommendations?
Solder braid/wick. It's absolutely phenomenal, although cleaning solder through holes seems to require an awful lot of the stuff comparatively, although I guess there is a lot more solder! It's not so much that the wick gets full of solder cleaning through holes, but by the time it's all sucked up then a lot of the flux nearby in the wick has been used, so you need to move along by about half an inch for the next hole or it won't really work.
But definitely, the holes end up all nice and clean with an ever so slight tinning... :)
My solder flux came today. :) Awesome stuff.
The flux I bought was ebay item 230807633527 from "catcrusader". Ordered Saturday, came first class Tuesday morning.
I also have solder flux paste and ChipQuik solder paste coming too, might try them on my GX4000s which are (for some weird reason) without ASICs..... see which method works best!
I have to say though, soldering the entire 200-odd pin QFP in 3 hours isn't bad, really - the flux made it soooo much easier. And having the Aoyue enabled me to get the chip off with no bent pins.
That's fantastic news!! Looks like it's all up and running too. Did you managed to get the cursor and light pen pins attached, I remember you were having trouble with those?
Looks like all you need to do now is clean up the excess flux and you're done - great job!
Yes, everything is connected properly now. Last time the colours would fade in and out, and some of the pins I had to wire up. But with the proper fluxing, every single pin was attached properly, even the ones at the top right I think, which are starting to come off the PCB (not surprisingly given this is about the 10th attempt at soldering the ASIC!).
I'm now trying to work out why my RoboCop II cartridge (which was dead) doesn't work now I've programmed the BR/BASIC cart onto an EPROM (I have an EPROM burner which supports 27C1001 now :) ).....
Just a thought - I was going to throw it away as it's dead, but does someone want a knackered ASIC? I might be useful for practising with if you want to try soldering a working one....
Very well done - must be an amazing feeling of achievement! From what I understand you didn't use the paste this time but the flux and some normal solder...? How did you melt it over the pins?
From what I've seen using solder paste means you could attach such a chip very quickly - will be interesting to see what results you get!
Out of curiosity, which EPROM burner have you got and where did you get it? Does it work with a PC and if so, over USB or does it require a Parallel port? Does it support Windows 7 (I have both 64 and 32bit) or is it more a DOS item...?
Can it also do EEPROMS and Flash?
I'm on the hunt for a new burner (my old one died a while ago and I'm realising I need one again).
Cheers,
Damien.
Quote from: Spirantho on 18:16, 26 June 12
Just a thought - I was going to throw it away as it's dead, but does someone want a knackered ASIC? I might be useful for practising with if you want to try soldering a working one....
There was a discussion a while back about sending custom ICs to a group who file the case off and reverse engineer the IC. Maybe your ASIC can be sent to them?
3 hours for one IC! That's quite a job.
@Dame1701: What kind of money do intend spending on an EPROM burner? How much do you intend using it and what ICs must it support? This is off topic, so send me a PM.
Bryce.
3 hours is a lot less than I spent on it the first time round. :)
My EPROM burner is a Wellon VP-490 - you can find them easily on eBay, and they support truckloads of devices. I've not really put it through any great trials yet, but so far it's been awesome, and very useful, especially with the TTL testing.
That's great thanks Spirantho, I'll check it out. Bryce, my apologies for the EPROM burner being question being off topic - I was inspired by the one of the posts in the thread. Have PM you!
I now have my 6128+ working and booting into BASIC! My VP-490 burned the 27C1001 like a champ, and I was soon struggling with a dodgy keyboard in BASIC. Actually, none of the keys worked at all, but I cleaned the contacts and it's better now - about half the keys work now!
Thanks to AndyCadley on this forum who very generously sent me his EME-157 disk drive, I am this close to a fully working CPC 6128+. Not too bad for less than £20 which is what it cost me....
(I just loaded The Hobbit from disk. Hurrah! :) )
QuoteJust a thought - I was going to throw it away as it's dead, but does someone want a knackered ASIC? I might be useful for practising with if you want to try soldering a working one....
[/size]
"
There was a discussion a while back about sending custom ICs to a group who file the case off and reverse engineer the IC. Maybe your ASIC can be sent to them?"Yeah! please contact them and send the asic.This can be a very good oportuniy to discovers the secrets of the asic.What cause the bugs,how is designed.
Please,please,please!!!.
visual6502.org HW Donation (http://www.visual6502.org/donate_hw.html)
PD:What the hell.I can't eliminate the \size to quote . :'(
Have just mailed them.... will let you all know the response. :)
For anyone interested in the progress of the original 6128+, by the way, here's a photo. :)
The keyboard is now fully working after I realised that the problem was the connector on the board, and that the cost-reduced CPC464 used the same mechanism.
All working nicely, cartridges (that's my burned EPROM in there!), disks, keyboard and everything. Yay!
QuoteHave just mailed them.... will let you all know the response.
Thanks!
Your cpc is very white.Wonderful.
Indeed, great specimen. And thanks for sending it! :)
Quote[size=78%]Have just mailed them.... will let you all know the response.[/size][size=78%] [/size]
[size=78%]
Any news?[/size]
Sorry, they never replied to me....