RetroB1977 Posted December 2, 2021 Share Posted December 2, 2021 Hi guys! I recently picked up an Amstrad PCW 8256 at an estate sale for $5. I found it in a barn on the property along with a Gateway 2000 4SX-33. When I got them home I did a smoke test. The Gateway works fine. The PCW showed an unstable green square and spun the disk drive before popping and smoking. Now when I try to turn it on it nothing happens. I looked for blown capacitors on the analog board but I can't find anything. If you have any suggestions please tell me. Thanks, RetroB1977 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/ Share on other sites More sharing options...
RetroB1977 Posted December 2, 2021 Author Share Posted December 2, 2021 Would it be possible to externally power the motherboard and then hook up a TV to the video output? I would think it would be a standard RGB signal. Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4959197 Share on other sites More sharing options...
oracle_jedi Posted December 3, 2021 Share Posted December 3, 2021 4 hours ago, RetroB1977 said: Would it be possible to externally power the motherboard and then hook up a TV to the video output? I would think it would be a standard RGB signal. It should be. RetroIsle has the schematics of the PCW. They are not a great scan but you might find better if you dig around. Looks like the motherboard itself needs +12V and +5V. There looks to be a +24V connector that is passed through to the printer. If I am reading this right, the video signal is coming off a large custom gate array and is available on the expansion port on pin 48, with a pin labelled NSYNC on pin 44. Ground looks to be pins 3, 4, 49 and 50. Of course all of this is speculation based on a bad scan. Proceed at your own risk, and good luck! 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4959325 Share on other sites More sharing options...
CatPix Posted December 3, 2021 Share Posted December 3, 2021 (edited) The 24 volts would be for powering the printer, so not required for a quick test. The video signal should be at least composite black and white; RGB might exist but pointless as the PCW is basically a CPC stuck in high res mod, which on the CPC/PCW is monochrome. Unlike the CPC, the PCW require a system disk to work (the ROM inside is merely a bootloader), so without one you'll be stuck with an empty screen. There are several how-to for replacing the original 3" drives with a 3"1/4 drive or a GoTek so you can more easily load software on it. For the popping issue I would check the power supply board first... Some failures may not be visible. Edited December 3, 2021 by CatPix 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4959649 Share on other sites More sharing options...
RetroB1977 Posted December 3, 2021 Author Share Posted December 3, 2021 Just now, CatPix said: The 24 volts would be for powering the printer, so not required for a quick test. The video signal should be at least composite black and white; RGB mgiht exist but pointless as the PCW is basically a CPC stuck in high res mod, which on the CPC/PCW is monochrome. Unlike the CPC, the PCW require a system disk to load, so without one you'll be stuck with an empty screen. There are several pages to replace the original 3" drives with a 3"1/4 drive or a GoTek so you can more easily load software on it. Okay. There is a little 4 pin video connector on the board. Do you know which pin is the composite? BTW, It came with a disk so I think it probably has the system on it. Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4959654 Share on other sites More sharing options...
CatPix Posted December 4, 2021 Share Posted December 4, 2021 (edited) If I'm to believe the monitor schematics : The 4 pin connector carry 2 grounds, sync video and the video signal. Really nothing dangerous for your TV or monitor so you could find a junked TV (just in case) and just try to tie the sync and video signals (pins 1 and 3) together in the RCA input. And ground on the ground of the RCA connector. (this is all video signal voltage, merely 1V you are absolutely safe to touch it and to poke it directly on your monitor input. If you can disconned all of the monitor connectors to be safe it's all the better according to the schematics, there should be a 3 pins connection that seems to be just the brightness controls, and a direct AC (120volts I assume) connection to the mains. If there's a connector, removing that one would ensure you made the monitor part totally safe. I found a cleaned and enlarged schematics : https://twitter.com/zigazou/status/1278416239388512256/photo/2 If the schematics are rights on the physical side, the pins should be 1/3/2/4, that is, video and sync then two grounds. Good news if you have the floppy , but they suffer from belt failure, you will need a new belt (I'd be utterly surprised if yours didn't broke!) https://www.ebay.fr/itm/231670658174?hash=item35f0a5b47e:g:KJEAAOSw2s1UzS5k Edited December 4, 2021 by CatPix Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4960022 Share on other sites More sharing options...
RetroB1977 Posted December 4, 2021 Author Share Posted December 4, 2021 1 hour ago, CatPix said: If I'm to believe the monitor schematics : The 4 pin connector carry 2 grounds, sync video and the video signal. Really nothing dangerous for your TV or monitor so you could find a junked TV (just in case) and just try to tie the sync and video signals (pins 1 and 3) together in the RCA input. And ground on the ground of the RCA connector. (this is all video signal voltage, merely 1V you are absolutely safe to touch it and to poke it directly on your monitor input. If you can disconned all of the monitor connectors to be safe it's all the better according to the schematics, there should be a 3 pins connection that seems to be just the brightness controls, and a direct AC (120volts I assume) connection to the mains. If there's a connector, removing that one would ensure you made the monitor part totally safe. I found a cleaned and enlarged schematics : https://twitter.com/zigazou/status/1278416239388512256/photo/2 If the schematics are rights on the physical side, the pins should be 1/3/2/4, that is, video and sync then two grounds. Good news if you have the floppy , but they suffer from belt failure, you will need a new belt (I'd be utterly surprised if yours didn't broke!) https://www.ebay.fr/itm/231670658174?hash=item35f0a5b47e:g:KJEAAOSw2s1UzS5k Thanks! The belt did indeed break. Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4960044 Share on other sites More sharing options...
RetroB1977 Posted December 5, 2021 Author Share Posted December 5, 2021 (edited) I still would like to get the monitor working. (Even just to use it as a cool looking composite monitor.) Here are some pictures of the analog board: If you need better shots of a certain component please ask. Edited December 5, 2021 by RetroB1977 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-4960877 Share on other sites More sharing options...
RetroB1977 Posted August 4, 2022 Author Share Posted August 4, 2022 I finally decided to work at this project again. I took the CRT board out and discovered a bulging capacitor, which I will try to replace. 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5100129 Share on other sites More sharing options...
+OLD CS1 Posted August 5, 2022 Share Posted August 5, 2022 Nothing like a little break to clear your mind 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5100283 Share on other sites More sharing options...
RetroB1977 Posted August 7, 2022 Author Share Posted August 7, 2022 I checked the voltage rails on the PSU output going to the motherboard. I only get 5V so the heater and flyback probably aren't getting power. I still don't see anything blown up... ? Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5101303 Share on other sites More sharing options...
RetroB1977 Posted August 30, 2022 Author Share Posted August 30, 2022 Is it possible for a capacitor to explode in a way that isn't visible? Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5114855 Share on other sites More sharing options...
YannAros Posted September 13, 2023 Share Posted September 13, 2023 I have acquired a PCW8512 which doesn't power up. First investigation showed me that the fuse is broken and R5001 is as well (showing an open circuit). R5001 is the big white resistor that can be seen in your 2 first pictures. I've ordered replacement resistors but haven't got them yet. Have you progressed in your repair since last year? If yes any advice on what to look at further? 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5315939 Share on other sites More sharing options...
RetroB1977 Posted September 13, 2023 Author Share Posted September 13, 2023 Well once I replaced that cap it had HV (I could hear it) for about 2 seconds before some transistors popped there tops (made the worst smell too). I'm not sure where I'll find a parts list for it so I've kinda given up. If you know a where I can get a parts list/schematic I may try and work on it some more. Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5316306 Share on other sites More sharing options...
YannAros Posted September 14, 2023 Share Posted September 14, 2023 The service manual is available here : https://acpc.me/ACME/AMSTRAD_PRO/AMSTRAD_PCW/DOCS_TECHNIQUES/SERVICE_MANUALS/PCW8256_Service_Manual[ENG].pdf Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5316536 Share on other sites More sharing options...
YannAros Posted September 15, 2023 Share Posted September 15, 2023 So replacing R5001 is not enough, at first power on it broke again together with R5002 this time. I saw also that D5007 seems bad, I will remove it to check. I believe more is broken behind, possibly IC5001 (STK7308), I do not know how to check this. Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5317432 Share on other sites More sharing options...
RetroB1977 Posted September 18, 2023 Author Share Posted September 18, 2023 Sounds like something is shorted, possibly a capacitor? Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5319016 Share on other sites More sharing options...
YannAros Posted September 21, 2023 Share Posted September 21, 2023 I've progressed and found out the following is broken: The path highlighted in yellow is in short circuit, i.e. the transistor in IC5001 is always conducting. R5001 and R5002 got broken. In the protection circuit, Q5001 and D5007 are also dead! I've ordered a new STK7308 (IC5001) and remaining broken components. I let you know! 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5320561 Share on other sites More sharing options...
YannAros Posted January 16 Share Posted January 16 I wanted to let you know where I ended up. Replacing STK7308 and other components that I've found broken didn't solve the issue, I even managed to break the new components. I, for some time, used a new meanwell power supply to provide +5V and +12V directly to the power board, by passing the high voltage stage and it worked without any issue (+24V is only required for the additional printer that I do not have) I finally found a broken PCW8256, missing the cpu board and keyboard, for cheap and transplanted its analog board, now I have a fully functional PCW8512. 1 Quote Link to comment https://forums.atariage.com/topic/327867-amstrad-pcw8256-repair/#findComment-5389842 Share on other sites More sharing options...
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