CPC 6128+ Problem - Maybe the RAM needs to be replaced?

[TheRogue]

Hi there, I just received a CPC 6128 Plus from the UK. I constructed a monitor cable to connect it to a Commodore 1084S, and acquired an appropriate power supply. Excitedly I powered it up, only to find a blue screen with AMS in the corner. I powered it off and on a few more times, sometimes getting AMS again, sometimes getting Amstrad Microcompu or various other incomplete variations of the boot screen. I opened it up and reseated the one socketed chip and tried again, same result. I set LK04 to 60Hz (I'm in canada) and then I got a longer but still incomplete boot screen. After flicking it on and off a few times I finally got it to the selection for Burnin Rubber or Basic. Burnin Rubber works fine. After flicking it on and off several more times I got the selection screen again, this time I selected basic and was met with a garbled screen. I set the autoload CP/M LK and tried it with a CP/M+ disk. No luck. I tried without the disk and got it to load directly into basic. I typed |CPM and was met with a garbled screen. It seems to me that things go spotty whenever the machine tries to access RAM so I am guessing I need to change the RAM. However, if any of you know differently, please let me know what I should do. The CPC is totally unheard of in Canada, and I may never get another 6128 Plus so please help me fix it!

EDIT: I forgot to mention that Basic will sometimes also load right from the Basic/Burnin Rubber screen, and also that the floppy disk drive light comes on and remains on. I have checked that the cable is the right way around.

[ukmarkh]

It sounds to me like the cart needs cleaning... just take it out and clean the contacts, normally taking the cart out and pushing it back in a few times fixes the issue.

[TheRogue]

What about the disk drive staying on? That can be caused by a dirty cart too?

EDIT: I have checked and the drive light stays on even with no cart present. Also, I got it to load basic, typed |CPM again and it says No disk present Retry Ignore Cancel so it seems to be more then just the cart.

EDIT2: It does seem to be something to do with the cart. I have successfully loaded software from an external 3-1/2" disk, the belt in the internal drive was kaput. I have ordered new belts. It seems to be the female edge connector. I think it has gone bad. Possibly it is also the cart itself, perhaps the data in the EPROM has become unstable. Either way I'm far less discouraged then I was before. This does seem to be fixable. Any thoughts?

EDIT3: I tightened up the pins in the edge connector and cleaned the cart and the issue persists. I think it may be a problem with the EPROM in the cart or possibly something else. By the way, when I connect my Symbiface II I have only successfully got the machine to boot once, every other time I get the incomplete boot screen or even just a blank blue screen as long as the symbiface II is connected.

[arnoldemu]

socketed chip and tried again, same result. I set LK04 to 60Hz (I'm in canada) and then I got a longer but still incomplete boot screen. After flicking it on and off a few times I finally got it to the selection for Burnin Rubber or

btw, 60Hz link is only respected by BASIC. If games do not re-program the video hardware then these will work too. If they re-program the video hardware then these games will not show a stable picture.

If you're using an Amstrad monitor (I think you said you were using an Amiga one??) then you don't need to set the LK.

If you get it working I would be interested to know which games work ok at 60Hz......

[arnoldemu]

What about the disk drive staying on? That can be caused by a dirty cart too?

EDIT: I have checked and the drive light stays on even with no cart present. Also, I got it to load basic, typed |CPM again and it says No disk present Retry Ignore Cancel so it seems to be more then just the cart.

The disc drive light on:
1. The disc drive may have been removed and the cable plugged in the wrong way.
2. The disc missing could also be a cause of the cable being the wrong way, OR, the rubber belt inside the drive has failed and needs replacement. I think info is on the wiki to tell you the dimensions of the belt to use.

EDIT2: It does seem to be something to do with the cart. I have successfully loaded software from an external 3-1/2" disk, the belt in the internal drive was kaput. I have ordered new belts. It seems to be the female edge connector. I think it has gone bad. Possibly it is also the cart itself, perhaps the data in the EPROM has become unstable. Either way I'm far less discouraged then I was before. This does seem to be fixable. Any thoughts?

cleaning the contacts using a white eraser is normally good enough, but also try blowing some air into the connector inside the computer in case there is dust in there.
I've not known a cart to fail, but it is possible. Inside the cpc6128 is a small daughter board which the cart connects to, maybe there is a bad connection on this?

Some of the symptoms seem to point to ram, but it may just be a dry joint that needs to be resoldered. Have you got the skills and kit to check the voltages on all the RAM chips?

EDIT3: I tightened up the pins in the edge connector and cleaned the cart and the issue persists. I think it may be a problem with the EPROM in the cart or possibly something else. By the way, when I connect my Symbiface II I have only successfully got the machine to boot once, every other time I get the incomplete boot screen or even just a blank blue screen as long as the symbiface II is connected.

To me this indicates a bad connection or possibly a short.

You got a blue screen with some text on it: Ok, so most of the rom is being read ok and the protection chip inside the cart seems to be running.

You managed to get a game to load.. well this again points to a good cart.

If you really suspect it you can get some from the UK ebay, a guy on there is always selling them.
(john thackeray is his name).

Could you do a visual inspection of the board on both sides and look to see if any of the solder joints look bad?

[TheRogue]

The funny thing is, even though the drive light is always on, it still loads software ok. The 3" drive does not work, but this is due to the belt being bad. I hooked up an external 3-1/2" drive that I modified myself with A/B and side switches and even though it's light stays on, it still successfully loads software. If I turn the CPC on and off many times, eventually it will load the BASIC / Burnin Rubber boot screen successfully, but like I said only if my SymbiFaceII is not connected, I only managed to load successfully once with the Symbiface connected. I believe this reinforces the idea that it is either a RAM or ROM (probably ROM) problem, as the Symbiface adds extra banks of both and if one ROM is bad this could complicate things. I do have a Volt meter I could use to check voltages, but I don't (yet) have an oscilloscope. I found a webpage I can get carts from for 7GBP per cart, so I think I will buy a few and see how that turns out. If that doesn't work I will also change the 4 41464 RAM chips on the mobo and see if that helps. If that doesn't I will change every chip on the board (except the ASICs as I can't source them and don't have access to SMD soldering equipment) and hope for the best. If THAT doesn't work, I guess i'll be in the market for a new 6128 Plus Mobo if anyone has one laying around. Let me know what you think

[TFM]

... when I connect my Symbiface II I have only successfully got the machine to boot once, every other time I get the incomplete boot screen or even just a blank blue screen as long as the symbiface II is connected.

Well, the SF2 is not built for the Plus, in principle it runs with it, but there may be some issues. Better use it with the CPC old generation. However since the SF2 has it's own power supply, this shouldn't be the problem.

Silly question: Is your power supply strong enough?

[dragon]

(except the ASICs as I can't source them and don't have access to SMD soldering equipment)

The asic is here:http://www.donberg.ie/descript/4/40489.htm

To test ram or asic in plus,I think the best way is burn a eeprom with the test cartridge.That's what it was designed.

If you want another.I  only  know this:

http://www.todocoleccion.net/amstrad-cpc-6128-plus~x17735696

[TheRogue]

Silly question: Is your power supply strong enough?

I have a 5V 2.5A switching power supply. I will try an ATX supply when I get home just to make sure that is not the issue. I will maybe buy that 6128 Plus if I cannot sort this issue out. Thanks a lot. I'm looking to buy an EPROM burner right now, so I will try to burn the test cart when I get it. Any other ideas guys!

[ukmarkh]

TFM/FS I was just thinking that about the Power not being strong enough. I seem to remember having a similar problem in the past. As for SymbiFaceII, works effortlessley with my 6128 Plus, and see's both my USB connector, external 3.5" F.D.D and most importantly boots up fine. So not better to use with a stock CPC, as it works fine with both.

[TheRogue]

I switched over to an ATX supply with EXACTLY the same effect. If I can only get it to boot symbos again, I am going to try to load the required ROMs into banks 0 and 7 of the symbiface and try to bypass the cart all together. I've NEVER used the symbiface before, so can anyone give me tips on accomplishing this. I have heard speculation about it but I don't know if it's ever been done before.

[arnoldemu]

The funny thing is, even though the drive light is always on, it still loads software ok.

I had a CPC6128 with a drive like this. In fact when the drive loaded the light turned off! so it was on when inactive and off when active

If I turn the CPC on and off many times, eventually it will load the BASIC / Burnin Rubber boot screen successfully, but like I said only if my SymbiFaceII is not connected, I only managed to load successfully once with the Symbiface connected. I believe this

Question: What do you see?

On on cartridge game, No exit, if it fails to start the screen is all one colour with little black horizontal lines on it. These are moving up the screen.

Do you see this, or do you always see the blue background and some yellow text?

Question: How is your symbiface 2 connected? Do you have a connector between the two, e.g. a converter which takes the cpc+ connectors and makes an edge connector and then the symbiface is plugged into this?

I had some hardware on the CPC that caused it to not start up correct and this was due to the hardware not being connected on the back correct, I had misaligned the connector on the cpc6128's edge connector. As a result I got all kinds of crashes and bad startups. Maybe this is what is happenign with your symbiface.

reinforces the idea that it is either a RAM or ROM (probably ROM) problem, as the Symbiface adds extra banks of both and if one

if you see the single colour screen often then the ACID protection chip inside the Cartridge could be bad or needs resoldering....
this indicates communication with it has not been good.

If it were rom then i would not expect so much to load ok, or for it to be really unstable.

If it were ram I would expect lots of crashes too.

I think try another cartridge first....

I use a ATX power supply with my cpc6128 and it works fine as long as I switch it on first then the cpc.

Another thing to consider is that possibly the power switch on the 6128+ needs cleaning or resoldering?
Maybe this is not engaging correctly when you insert a cart?

Maybe it just needs some WD40

[TheRogue]

The symbiface is connected with a CPC+ cable supplied by Prodatron. This wouldn't be the problem anyway as there are issues when the symbiface is not connected. I will sometimes get a blank blue screen when the symbiface is connected, but when it is not, I always get SOME text on the screen, sometimes it is just the first few letters of the word AMSTRAD, sometimes a few lines of the bootscreen, sometimes the text will be slightly corrupted. Also, sometimes there will be a few VERY SMALL (~1-2 centimeter single pixel-row) lines of random static, but they are stable and unmoving.  One thing to note, is when it does load the OS successfully, it has NEVER crashed. The issue is just getting it to load up. It's a real stumper...

[ivarf]

One thing to note, is when it does load the OS successfully, it has NEVER crashed. The issue is just getting it to load up.

Surely this would imply  that the RAM is 100% OK?

[TheRogue]

I SOLVED IT! One pin on the ACID was unsoldered! Completely bare! One dab of solder and I have a working CPC!!

HUZZAH!

[arnoldemu]

I SOLVED IT! One pin on the ACID was unsoldered! Completely bare! One dab of solder and I have a working CPC!!

HUZZAH!

excellent news.

[redbox]

What a great thread - my 6128+ is prone to random crashes and it seems to be when the Plus features are being used.  Maybe some of it should go in the wiki?

Now I will check my ASIC and also the cartridge slot/daughter board for dry joints etc. 

[arnoldemu]

What a great thread - my 6128+ is prone to random crashes and it seems to be when the Plus features are being used.  Maybe some of it should go in the wiki?

Now I will check my ASIC and also the cartridge slot/daughter board for dry joints etc. 

check the joints on the ACID protection chip inside the cartridge too as TheRogue did.

Seems the acid/asic must be checking in with each other.

[redbox]

check the joints on the ACID protection chip inside the cartridge too as TheRogue did.
Seems the acid/asic must be checking in with each other.

Good point - my initial thought was that it was a problem with the cartridge so will do this as well.

[TFM]

I switched over to an ATX supply with EXACTLY the same effect. If I can only get it to boot symbos again, I am going to try to load the required ROMs into banks 0 and 7 of the symbiface and try to bypass the cart all together. I've NEVER used the symbiface before, so can anyone give me tips on accomplishing this. I have heard speculation about it but I don't know if it's ever been done before.

The SF2 can't emulate the lower ROM, so this idea will work only half way.
If you have a concrete question about the SF2, let me know.

Edit: Congratulations to find the ACID problem :-)))))

[TheRogue]

I've been away for a while so haven't really had a chance to play with my 6128 Plus since I got it working, but man am I ever happy it functions! I can't wait to really dive into it! As I mentioned before, I'm from Canada, and the CPC is just about unknown here. I have been collecting, using, and enjoying classic computers and game consoles for about 15 or so years (since I was 5 or 6) and I have acquired just about every machine that was ever popular all over the world, but the CPC has eluded me until now. I'm not one of those wankers who collects computers to keep them in a case and look at them though. I use every one of my machines, and not just for a day or so to make sure it works. Consistently. I'm also quite a prolific modder, with all my machines possessing the best mods and modern upgrades I can acquire. I would like to get into the CPC scene, and help out if possible. I'm pretty good with hardware, having done quite a few repairs and hardware intensive mods without ever damaging a machine in the process. Next up on the mod list is a cassette port for my 6128. I have the parts ready, and I'm going to do it tomorrow when I get home from college. Wish me luck!