Hi all,
I finally got my long-coveted CPC6128 hardware, sans monitor/power supply, and have been trying to debug its setup this evening .. for this bit of retro-tastic adventure I purchased one of the SCART cables from retrocomputershack.com, which were recommended to me by other Amstrad aficionado's, and I have an HxC (Rev F) drive as well, for when I eventually get the machine up and running.
To give it a quick test today, I wired it up with a 5V/4A power supply, proper polarity, just to see if I could get something on the screen - alas, it is not to be. The seller provided me with a video of the system working before he shipped it, so its got to be my problem I suppose.
The question I have is, do I have to have both 5v and 12v wired up in order to get it to boot properly - or is it such that I could operate it without the disc drive being powered up? I don't have the barrel adapter required to get a 12v supply wired up to it yet, so I was kind of hoping I would be able to do this with just the 5V adapter .. anyone wanna clue me in on my stupidity here?
I'm not getting very good results - the TV I am using (SABA) is decent quality and works with my other retro systems just fine (Oric Atmos and C64), so I know its not the monitor at least .. so perhaps I've just gotten too ahead of myself and need to go to the hardware shop to get the required parts to make the 12v lead?
Or .. *shudder* .. have I screwed things up by trying to power up the CPC6128 with just 5V alone? Also, the fact that its a 4A adapter - does this mean I've potentially screwed my system, which everything I've read on the Internet says should "just work" with a "5V/2A" adapter .. I sure hope that I haven't fried anything. Or, if I have, I'll be starting a new thread to discuss my debugging and replacement of fried parts, alas ..
5V alone, is all the CPC needs to power up. 12V is only for the disc drive and if using Gotek, you don't need 12V either.
Hmm if the polarity is fine, the connector the right size and power supply is kicking out 4a at 5v that should be more than sufficient to boot to basic. Does your led come on when using the power switch?
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If you get an led, using delete key try deleting something got should get a beeping sound out the speaker too.
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Quote from: ibisum on 21:07, 07 May 18
Or .. *shudder* .. have I screwed things up by trying to power up the CPC6128 with just 5V alone? Also, the fact that its a 4A adapter - does this mean I've potentially screwed my system, which everything I've read on the Internet says should "just work" with a "5V/2A" adapter .. I sure hope that I haven't fried anything. Or, if I have, I'll be starting a new thread to discuss my debugging and replacement of fried parts, alas ..
I run all my CPC's on 4 Amp supplies. The supply can go up to 4 amps but will only supply what the CPC needs. So you are fine.
I did a quick and messy video on my phone at Christmas when a known good CPC came out of storage and it wouldn't turn on:
http://www.youtube.com/watch?v=KlE7w0qRzsY
Basically your first port of call if you have no light on the LED is the power switch. No need to replace it, it just needs contact cleaner and it will be as good as new after its been switched a few times.
Thanks for the helpful replies guys - and sorry for the newbie question, I've since learned that this is a FAQ in this forum and I appreciate your patience.
So the symptoms are: the machine starts up, it clearly gets power - the LED on the floppy and on the main case unit both come on, and there is a flicker on the screen when I turn the switch on - however, pressing DEL does not result in any sound, nor do I get anything legible on the screen at all. There are just three flickery lines, each a different colour (red/blue/green) which don't seem to go away when I turn the CPC6128 off and on.. so I'm not sure if these are an artefact of the CPC612's condition, or just a side-effect of my ancient TV doing 'something' with the SCART signal (and just to confirm this TV works great with other micro's such as my Atmos) .. I don't have a floppy disc yet (was planning on going straight to HxC) so I can't do a floppy "CAT" test (as is recommended elsewhere) to see if there is any response on the drive, alas.
So I'm a bit stumped - it would appear that I have to go through the "more intensive debug" dance: GA, RAM, Z80 cpu, etc. Drats, I was kind of hoping to avoid opening the case so soon. ;)
Anyway I'm going to wire up a proper cable to give me 12v just so I can see if the floppy works with a "CAT" command, and .. if that produces nothing, I'll pop the case and start going through the debug dance ..
Did you buy it working on eBay or with paypal? If so talk to the seller about a refund these are robust machines so seems unlikely it broke in the post.
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Quote from: ibisum on 07:20, 08 May 18
Thanks for the helpful replies guys - and sorry for the newbie question, I've since learned that this is a FAQ in this forum and I appreciate your patience.
So the symptoms are: the machine starts up, it clearly gets power - the LED on the floppy and on the main case unit both come on, and there is a flicker on the screen when I turn the switch on - however, pressing DEL does not result in any sound, nor do I get anything legible on the screen at all. There are just three flickery lines, each a different colour (red/blue/green) which don't seem to go away when I turn the CPC6128 off and on.. so I'm not sure if these are an artefact of the CPC612's condition, or just a side-effect of my ancient TV doing 'something' with the SCART signal (and just to confirm this TV works great with other micro's such as my Atmos) .. I don't have a floppy disc yet (was planning on going straight to HxC) so I can't do a floppy "CAT" test (as is recommended elsewhere) to see if there is any response on the drive, alas.
So I'm a bit stumped - it would appear that I have to go through the "more intensive debug" dance: GA, RAM, Z80 cpu, etc. Drats, I was kind of hoping to avoid opening the case so soon. ;)
Anyway I'm going to wire up a proper cable to give me 12v just so I can see if the floppy works with a "CAT" command, and .. if that produces nothing, I'll pop the case and start going through the debug dance ..
Can you provide a photo of the screen please
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@tjohnson (http://www.cpcwiki.eu/forum/index.php?action=profile;u=2129): by Paypal, and I've been in touch with the seller, he's a good bloke. I trust he didn't sell me dodgy gear, so I'm quite willing to work through this issue if I can .. part of what I got it for is to get a few burnt fingers here and there .. ;) Its the retro-lovin' lifestyle.
@CraigsBar: Sure, here you go - sorry for the potato quality image, but I think you can see the effect nevertheless - it should be noted that these lines appear whether there is power attached to the CPC6128 or not, which makes me a little suspicious of the SCART cable, actually .. I do have another one that I could try, although it is a different configuration than this one from RetroComputerShack ..
Where do you live there might be a member able to help locally
Quote from: ibisum on 10:32, 08 May 18
@tjohnson (http://www.cpcwiki.eu/forum/index.php?action=profile;u=2129): by Paypal, and I've been in touch with the seller, he's a good bloke. I trust he didn't sell me dodgy gear, so I'm quite willing to work through this issue if I can .. part of what I got it for is to get a few burnt fingers here and there .. ;) Its the retro-lovin' lifestyle.
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@tjohnson (http://www.cpcwiki.eu/forum/index.php?action=profile;u=2129) I'm in Vienna, Austria - I do have plans to have a Retro- meet up at the local hackerspace (Metalab) in the next week or so and I'm sure there are other Amstrad users out there, but I'd honestly prefer to go to that meeting with a working Amstrad rather than spend time debugging it .. ;D .. so thats why I'm busy bugging you experts about it, lol ..
.. okay just as a followup, I've tried the second SCART cable (with a 9v battery lead to provide power to SCART) and I get exactly the same result .. interesting thing is that the lines show up with the second cable, even unattached to the Amstrad, so I guess this is a red herring in that its just 'normal' display for a non-driven SCART cable (i.e. when it doesn't get a signal from the computer) .. and just to be sure, I hooked up my Atmos to verify the monitor is still working and there is no issue there, its a perfectly stable picture.
So I guess the CPC is just plain dead, and I've gotta open it up, give it a clean, check for bad RAM, bad Z80, etc.
One thing I just noticed - I double-checked the rating of the power supply I'm using, and even though its says it provides 4A, my meter shows only 2A been provided (and yes, its for sure 5V) - so maybe one last thing I can do before I start the long road of debugging components, is find another power supply that I know for sure provides >2.4A, as I've seen a lot of comments that the CPC is very finicky about this. Had a similar problem with my Atmos when I powered it up, had to go through a few power supplies .. I've got a PC power supply that provides both 5V and 12V in the one connector, so I'll go get parts this afternoon to make a cable and see if that will give me a better result.
Thanks again folks!
Hi ibisum,
first, to clear things up about power supplies, devices and amps: The amps stated on a PSU is what it CAN supply. The amps rating written on the CPC is what it needs AT MOST. Devices only take what they need: Converting amps to beer: My local pub CAN supply 1000's of litres of beer (PSU rating), my record consumption lies somewhere around 12 Litres (CPC rating), however during a standard evening in the pub I only drink 3 Litres (what you're reading from the meter).
So the 4A on your PSU is correct, as is the 2.4A on the CPC, but... 2A for an idling CPC seems a lot, looks like something has failed in there. You could try reseating the socketed ICs, but I suspect there is something more serious going on.
Bryce.
@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) Thanks for the clarification - its clear now, re: amps.
But, I did not measure the amps while the Amstrad was plugged in - just, with my multimeter. So its not the Amstrad providing such a load, but the meter - which I guess, is not an accurate way of measuring amperage on the wire?
Anyway, I'm off to the shops to get a few more power supply bits, so maybe .. hopefully .. I'll have some good news in the next few hours.
You can't measure amps without a load, because the load decides how many amps will flow. That still makes the 2A reading quite suspect, because (assuming you were using the meter correctly) inside your meter there's more or less a copper bar (known as a shunt) shorting the two probes. In reality the shunt is a known resistance of very low value. The meter calculates the amps, by measuring the voltage before and after the shunt and then uses ohms law to calulate what the current is. (Vin - Vout / Shunt resistance = Amps).
However, if no load was present, then you are essentially shorting the power supply which should cause the PSU to try to supply as much current as possible. In an expensive PSU, this would probably cause a reading of maybe 10A, but the voltage would drop to about 2V or less. A cheap PSU would just go bang and some smoke would come out.
Bryce.
Yes, thats what I understood to be the case .. its not a super expensive supply and it works fine on other gear. Regardless, I'm off to get a new proven supply for this machine. I hope I can get some results today.
Quote from: tjohnson on 22:21, 07 May 18
If you get an led, using delete key try deleting something got should get a beeping sound out the speaker too.
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Try this. Press Del or CLR with the volume turned up on the CPC. If you get a beep that eliminates a lot of issues.
Quote from: ibisum on 07:20, 08 May 18
- however, pressing DEL does not result in any sound
Bryce.
Thats not definitive anyway, if was me, i try put a headphone in 3,5mm jack with the del key test. In the other hand yo can write a blind command, a | tape + ctrl + intro + a key example to view if the tape relay try to do something to avoid the del key. or press varius keys until he reach the top and generates the del sound.
Quote from: dragon on 19:26, 08 May 18
Thats not definitive anyway, if was me, i try put a headphone in 3,5mm jack with the del key test. In the other hand yo can write a blind command, a | tape + ctrl + intro + a key example to view if the tape relay try to do something to avoid the del key. or press varius keys until he reach the top and generates the del sound.
Turning the machine on and pressing del repeatably will generate a beeping sound but yes it is possible the speaker could be faulty
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Quote from: ibisum on 12:46, 08 May 18
Yes, thats what I understood to be the case .. its not a super expensive supply and it works fine on other gear. Regardless, I'm off to get a new proven supply for this machine. I hope I can get some results today.
what further progress?
Quote from: tjohnson on 18:19, 11 May 18
what further progress?
Probably like me and my French 464. Good advice from Bryce and other users but simply haven't had the time to take it apart yet. And I also have an Amiga 600 in bits awaiting parts. We're like your Dads mates who when you go to their house they own 10 old cars, most of which don't work as they need parts or fixing! :laugh:
Sorry guys - just a little bit behind the ball with this project at the moment .. my attempts to use my local power supplies haven't been fruitful, so the last thing I will do is try a PC power supply - but for that I have to make a trip to the hardware store for cable accessories .. some time today hopefully, so I can pick it up again this weekend and determine just how terrible (or not) things are with my CPC6128 .. I really appreciate the help so I'l be back with news shortly ..
Okay .. an update .. I bought a fresh 5V/3A adapter, and I've switched out the TV for another, different one. I also have a SCART/HDMI adapter now, and tried that too. No matter what: CPC6128 does not boot.
:(
Well, I now prepare my workbench for an evening of opening the case, re-seating what can be re-seated, and going through whatever test procedures I can find - I think I saw a test manual for the CPC6128 in this wiki somewhere, so I'll be studying that this evening. If anyone else has any other tips for dead-CPC recovery, I'm all ears ..
Here (http://www.cpcwiki.eu/index.php/Service_Manuals) you'll find the service manual.
Good luck!
Yeah, the service manual doesn't provide much useful info imho .. but I've since found a source for RAM chips and have ordered them, in case that is the issue (cross-fingers), and even if its not I figure it'd be good to have some spare .. so I got the MT4264-15's, which I've heard around the 'net are compatible ..
Anyway, I'm still working on recovering the machine - will let you guys know if I make progress. Tonight I'm just doing research; I'll break out the screwdriver some time tomorrow... hope I can feel a warm RAM chip, LOL!
What does the seller say about this? I find it strange that you were sold a working machine yet it doesn't work and now you are buying ram chips. Is there something you haven't told us?
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I trust that the seller sent me a working Amstrad - it just didn't work when it arrived. I'm prepared to do a bit of work to get it working - maybe all I need to do is re-seat a chip or two .. as far as getting the RAM chips already, they're useful for other systems too, don't forget. ;P
And before I throw this machine back to the seller, I really do want to try to recover it and get it working again. That's part of the fun of the retro scene, isn't it? And no, there is nothing I'm not sharing here - the machine simply hasn't powered on for me... yet. As far as I know, I'm not responsible for it not powering on properly (I did double-check all my power supplies with a meter before plugging them in...) I'm hoping I'll get it working with your help, though.
Quote from: ibisum on 20:55, 14 May 18
I trust that the seller sent me a working Amstrad - it just didn't work when it arrived. I'm prepared to do a bit of work to get it working - maybe all I need to do is re-seat a chip or two .. as far as getting the RAM chips already, they're useful for other systems too, don't forget. ;P
And before I throw this machine back to the seller, I really do want to try to recover it and get it working again. That's part of the fun of the retro scene, isn't it? And no, there is nothing I'm not sharing here - the machine simply hasn't powered on for me... yet. As far as I know, I'm not responsible for it not powering on properly (I did double-check all my power supplies with a meter before plugging them in...) I'm hoping I'll get it working with your help, though.
I guess a component could have come loose, on my 6128 the cpu and the 40010 gatearray are socketed but seems unlike they would dislodge in transit without the machine getting damaged in the process. I assume you didn't try and power it with a higher voltage than 5v by mistake, you seems clued up enough not to have done that.
I'm quite familiar with the power issues that we retro-enthusiasts have to deal with at times, so yeah .. the suspicion that I've fried it with a dodgy power supply, while discomforting to me personally, is still something I have to contend with. But I did measure the 5V supply before plugging it in the first time, and it just has not powered on.
So today I open the case and start the burnt-finger testing of chips to see if anything is particularly warm.
In the Oric/Atmos world (and elsewhere) we have a few docs that describe test-point procedures - i.e. look for this voltage X on pin Y, etc. No matter how I search, I don't seem to be able to locate a similar set of docs for the Amstrad world - the Service manual is woefully useless it seems, with a flow chart that just says ''replace these chips if you don't get video output'' .. but I'm wondering if any of you other enthusiasts have encountered a more detail test-point procedure for narrowing down the issues? I'm all for burnt-fingertip testing, lets see if it provides some insight into what is going on .. but if there is a more technical test-point procedure I'd love to know it.
Anyway, my next action will be: open the case, inspect for obvious damage (blown caps, are they a thing?), leave it on for 20 minutes, look for overheating chips, replace chips. Repeat until it boots.
My tips:
Check that the socketed chips are properly seated.
Caps: Not really an issue in the CPC world. There is only one critcal electrolytic on the power rail (just behind the power socket), it rarely leaks as it wasn't really put under any stress in its lifetime. Swap it anyway.
Check that you are definitely getting voltage to all the ICs. I usually check the power pins of IC105 (74LS153 beside the CRTC) This is one of the furtherest points from the power input. If it's anything below 4.8V then there may be something partially shorted somewhere.
Regarding RAM: Possibly defect, but there are more likely candidates if you are getting absolutely nothing on the screen. The Z80 and the CRTC would be the first things to check. The Z80 is easy to check because it's socketed, the CRTC means lots of soldering, but as an Oric owner, you probably have some experience swapping those rather dodgy ULA chips :D
Bryce.
Haha - my solution to the ULA problem on Oric has always just been: find another Oric. ;). (I have 7 of them now...)
Thanks for the tips - this is precisely what I was hoping for .. I'm going to open 'er up later this evening (Central European time) in the peace and quiet, and start probing around. I sure hope its not the CRTC or CPU .. those haven't been so easy to find online.. but I did just get confirmation that the RAM has shipped, so lets see ..
Either way, thanks again, I'll dutifully report back my findings. I know what its like when you see a new member get an old machine up and running again, hopefully you guys will share my joy when it happens ...
Both the CRTC and CPU are still available to buy. Regarding the Orics, if you want them repaired then let me know. I have a source for the ULAs. I'm also the proud owner of both an Oric 1 and an Atmos. I even managed to load a tape on the Oric 1 once (or was that just a dream?) :D
Bryce.
Good to know there's another Oric fan here .. well actually all my machines except for one Atmos, are now functioning .. I have the full suite, Oric-1 (x2), Atmos (x5), and even a Telestrat .. I'm an active contributor to the scene over on defence-force, and I have a couple Cumulus boards, as well as the brand-spanking new Twilighte+Sittler card which I just received last week, and if it weren't for the CPC6128 I'd be playing with Orix .. in case you haven't seen that yet, check it out - its bonkers: http://orix.oric.org. Basically, a Minix-like OS for Oric, with bank-switching features and other great peripherals, like USB, mass-storage, serial .. a second 6502 .. etc ..
(And if you are interested in my non-working Atmos as a fun project, I'd be quite happy to trade it for something Amstrad'ish of similar value/working-condition .. I think its just an ULA replacement, but .. with my CPC6128, who has time for that noise ..)
Anyway, we can talk Oric stuff elsewhere, glad to know I'm not the only one here with that particular lust ..
We can continue this discussion in a PM. I know someone who's interested in getting an Atmos, so I may take you up on that offer.
Bryce.
Just to follow this up .. We had a RetroSession at Metalab here in Vienna last night (https://metalab.at/wiki/RetroSessions) and I invited MaV, from this forum, to join us - and he did!
MaV very kindly assumed responsibility for case-opening duties - I guess curiosity as to the state of things overcame him, and after a brief intro and looking away to other attendees, I returned to find MaV with the CPC6128 in intimate embrace over the electronics workbench .. he'd gotten 'er opened up, and was sitting there cooing away at all the things that could be wrong.
It didn't take long. Every single RAM chip was heating up. :(
So, the conclusion is: probably I zapped the system when I first powered it on. The seller I obtained it from is trustworthy and provided me video of it booting prior to shipment - but, I guess I must have done something wrong with the 5v and 12v power supplies I'd prepared... the theory that MaV and I formulated after observing very hot RAM, was maybe I'd plugged in the 12v after all.
So, the system is fried.
That said, I've ordered a full replacement-chip kit for the CPC6128, as well as a full set of RAM chips for it - they should arrive next week, hopefully, and I will proceed - slowly and carefully, under controlled conditions of the Metalab electronics workshop - to start removing the dud RAM, putting in sockets, and so on.
So, as I make progress over the next few weeks, I'll keep you updated ... I'm committed to getting this system working again, and I am grateful for all the help - especially MaV and Bryce, who warned me I might have fried things all along. Ah well.
At the very least I can provide some full-chip-replacement-olympics amusement as I plod along.
I might add:
The main chips all had 4,6V at the Vcc pin, which seems ok if a little low. I suspect other components might have been fried as well, i.e. resistors and such, capacitors probably not because most of them on the board can take 12 volts, AFAIK. I didn't check on the glue logic and the FDC, the latter is important for stage 2, once the system shows the basic screen. The 74-series chips will need a bit of investigation after the main components are replaced, I presume.
The screen was black all the time, no flickering at all, which leads me to suspect that the CRTC and/or Gate Array are gone to meet the maker. The keyboard backspace key did not lead to the expected beep and I assume that the 8255 and AY-chip are compromised as well (alternatively: they might be ok, but the ROMs are fried, so the Z80 cannot initialise them properly).
I also checked the Z80 pins mreq and halt and they seemed to do their job. We'd need further investigation with a scope, but at the state the CPC is in I think ibisum should start with replacing the RAM chips first (and put sockets in first). The GAL, the Z80, and the GA are socketed, as is usual I guess, some things therefore can be tested more easily.
The question now is: Is it safe to replace the chips one by one in a certain pattern, then check in between whether the system starts to work or not, or will it need the full replacement anyway and ibisum is having to face a lot of work ahead?
Oh dear not good, I did ask a while ago if you managed to put a higher voltage into the machine which caused you some discomfort.
Re. resistors I'm sure someone more knowledgeable than me may chip in but they tend not to be voltage specific but rated on current e.g. 1/8w.
I think it would be ok to swap individual components until you find the ones that have blown.
Yeah, so I'll start the RAM socket installation some time next week, once I receive a replacement RAM set .. I seem to recall someone saying its possible to sit a replacement chip on top of the old one, without soldering it, to serve as a means of detecting bad RAM - i.e. with new, good chip on top, the old one functions .. wonder if that is worth the effort or if I should just rip them all out?
MaV and I noticed that every single RAM chip seemed to have heating issues - they were very hot after 10 minutes of power being applied. I wonder -could they all be bad, or is something further upstream possibly bad .. hmm .. well anyway, it can't hurt to socket the chips, and I've got good desoldering equipment at the lab anyway ..
Quote from: MaV on 11:13, 26 May 18
I might add:
The main chips all had 4,6V at the Vcc pin, which seems ok if a little low. I suspect other components might have been fried as well, i.e. resistors and such, capacitors probably not because most of them on the board can take 12 volts, AFAIK. I didn't check on the glue logic and the FDC, the latter is important for stage 2, once the system shows the basic screen. The 74-series chips will need a bit of investigation after the main components are replaced, I presume.
The screen was black all the time, no flickering at all, which leads me to suspect that the CRTC and/or Gate Array are gone to meet the maker. The keyboard backspace key did not lead to the expected beep and I assume that the 8255 and AY-chip are compromised as well (alternatively: they might be ok, but the ROMs are fried, so the Z80 cannot initialise them properly).
I also checked the Z80 pins mreq and halt and they seemed to do their job. We'd need further investigation with a scope, but at the state the CPC is in I think ibisum should start with replacing the RAM chips first (and put sockets in first). The GAL, the Z80, and the GA are socketed, as is usual I guess, some things therefore can be tested more easily.
The question now is: Is it safe to replace the chips one by one in a certain pattern, then check in between whether the system starts to work or not, or will it need the full replacement anyway and ibisum is having to face a lot of work ahead?
With the screen black all the time, there is for sure something else wrong than RAM. Failing "RAM" would just give you a grey screen with black border. I quoted RAM because the symptom can come from anything related to RAM access.
Full black screen can be caused by Z80 / ROM / CRTC / GA .
So after removing the heating RAM, try to get to that grey screen with black border first. Then mount the new RAM.
Quote from: geraldWith the screen black all the time, there is for sure something else wrong than RAM. Failing "RAM" would just give you a grey screen with black border. I quoted RAM because the symptom can come from anything related to RAM access.
Full black screen can be caused by Z80 / ROM / CRTC / GA .
So after removing the heating RAM, try to get to that grey screen with black border first. Then mount the new RAM.
Grey screen, black border. Thanks for the info.
I wouldn't know that because my CPCs are all in good working condition. /me knocks on wood.
Quote from: tjohnsonRe. resistors I'm sure someone more knowledgeable than me may chip in but they tend not to be voltage specific but rated on current e.g. 1/8w.
Yes. I was just guessing that some of the blown components might even cause a short somewhere, which in turn causes resistors to malfunction due to running out of spec.
Quote from: ibisumthey were very hot after 10 minutes of power being applied
More like after 10 to 15 seconds, really. While probing the pins on the other chips I made sure to switch the CPC off after every two, three attempts just to make sure the broken RAM chips are not getting too hot and damaging other parts.
I added pics in case its of interest - perhaps some of you Amstrad gurus can take a closer look at the chipset and let me know of any gotchas/interesting details I don't know yet:
https://metalab.at/wiki/RetroSessions
If most ICs are measuring 4.6V on VCC then one or more ICs are shorted inside. I'd remove the RAM first and power it up again to measure VCC. Then start removing the AY (the AY is very voltage sensitive) and then the TTL chips one by one a re-measure VCC each time until it gets back to 5V. When you've got to 5V you can start putting the new ICs in and see if it boots. It's a long repair ahead of you though. Don't start removing the CRTC or 765 until you've removed the AY/TTLs and confirmed that VCC is still being pulled low. The analogue ICs in the amplifier section are probably ok, they could take 12V, but everything else could potentially die at anything above 5.25V. That's what the specs say.
Bryce.
Cool, thanks for the advice Bryce - I'll be doing this surgery some time later in the week, will keep you posted - and I'll be sure to follow your advice very closely. Great info!
If you're really lucky, sometimes the RAM will have shorted the 12V so fast that it protected the other ICs from damage. I've seen this happen a few times (not just on CPCs). A fully shorted IC can pull the rail back down to 5V or lower.
Bryce.
Interesting! I'll be sure to follow the test procedure rigorously after I get the RAM removed ..
Just an update .. this chip kit arrived today, seems to have a majority of what I might need to replace:
https://www.ebay.com/itm/Zilog-Z80-Amstrad-CPC-6128-Homebrew-IC-Kit/151327810599?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Still waiting for the RAM replacement kit, however .. as soon as that arrives, I will attempt resuscitation...
No idea why the seller associates this bundle with the CPC 6128. The majority of the ICs are not used in the Amstrad.
Bryce.
Smart seller definately not China prices tapping into the retro revival
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Well, taking a glance at the CPC 6128 schematics and taking the RAM chips already in account, this leaves ibisum short of at least one of each:
74hcuo04
73ls32
74hc132 or 74ls132
74ls145
74ls153
74ls244
74ls273 or 74hc273
74ls373
PAL 16L8AC
Gate Array 40010
Since Bryce proposed checking on the TTL chips first, the batch above will be absolutely necessary for repairs.
Yes, but after swapping the RAM and having known good CPU, GA and CRTC:
If you still have a completely black screen (no border) then swap the 74LS153s (RAM Multiplexers), the 74LS244 and the 74LS373 (RAM i/o buffers).
If the GA isn't reacting (not outputing a clock signal to the CPU) swap 74LS132 (IC110 - Reset, GA enable and printer port circuits)
If it boots to a blue screen but doesn't get to the ready signal swap the ROMs.
74LS145 - Only swap if the AY is new and the keyboard still doesn't work.
74LS273 - Only swap if the printer port isn't working.
Bryce.
Hehe .. I'm kind of getting the feeling I should a) ship this unit to Bryce to fix, and b) go look for another deal on a CPC6128 that I won't blow up this time. :P
Send it over if you like.
Bryce.
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Nope, gonna wait for the RAM, do that, then see what else happens. I remain committed to the cause; when it finally boots, this machine is gonna get a lot of love.
Quote from: ibisum on 18:00, 14 May 18
I've since found a source for RAM chips and have ordered them
I have a feeling I'm going to be needing some RAM chips soon as well. Where did you find them?
Quote from: llopis on 16:44, 15 June 18
I have a feeling I'm going to be needing some RAM chips soon as well. Where did you find them?
EBay, and .. it turned out to be not so great .. I need more chips too.
What happened on the eBay?
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I didn't get enough chips, and some of the ones I did get were bad.
Anyway, I ended up just getting another CPC6128 for my needs for now, as well as a PCB that I could use to harvest parts, hopefully, to recover the other one some day. I'll just get my CPC6128-related project started with the newer machine, in the meantime, though ..
Did you just try changing the memory?
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No .. I used a friends RAM-tester (set up for another project), found that the set that I ordered had a few duds, and decided to just get another CPC6128. I'll definitely have this set of parts available for next time .. and I do intend to repair the original which I (more than likely) borked myself, but for now I'm moving on and putting the Amstrad to use as intended, with an M4 board which should hopefully arrive this week.
Thanks to MaV and Bryce, and the rest of the gang too, for all the support - you should rest happy knowing that there's another Amstrad fan out here with at least enough parts (probably) to build another CPC6128 one day in the future. ;)
Oh man, so you ask for the borked 6128? Keep it for a meet and repair session
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I borked one CPC6128, I believe, myself. Then I got parts intending to fix it. Then I ran into problems getting all the parts I would need to do a replacement. Then my M4 board showed up. I decided to get another CPC anyway, so I did.
I will get the original project done - CPC with M4 board, doing stuff at a local hackrrspace.
And then, some day in the near future, I will return to the borked CPC and fix it.
While it is a shame and a pity that I borked a CPC, I did gain a lot of experience and most importantly, made contact with MaV here in Vienna, and it looks like we'll be pushing things forward as Amstrad users in our next RetroSession @ Metalab soon.
So its not all bad news. :)
Anyway, I will definitely put the borked CPC on the workbench some time this year and get back with a progress report .. its just that I have the M4+Amstrad, plus the TwilighteBoard+Oric, to get set up and put into use in demonstrating effective modernisation of our retro- collection ..
What's a TwilighteBoard?
Bryce.
Bryce - its a modern board made for the Oric-1/Atmos machines, which gives us amazing capabilities, akin to what has been provided for the Amstrad community by the M4 board... details here:
http://orix.oric.org/hardware/twilighte-card-v0-3/
At the RetroSessions/Metalab here in Vienna, I'm pursuing the goal of regular demonstrations of older, archaic technology, being given new life through modern accessories such as the M4 board and Twilighte and others (Cumulus, etc.). We have a lot of IoT and ESP8266/ESP32-style hacking projects going on at Metalab, and the goal is to use the older 8-bit machines as an interface to some of these kinds of projects.
Just as a followup and completion for this thread - I ended up just getting another CPC6128 for my needs, and will be working on recovering the one I borked over the next few months.. its not a priority given that I have another setup working, and can continue my Retro explorations with it ..
Thanks for all the help guys - this thread has been very useful.