Jump to content
IGNORED

Amstrad PCW8256 Repair


Recommended Posts

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 

 

 

 

B1311259-DC78-46DA-BC10-50717A7A7655.jpeg

Link to comment
Share on other sites

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!

 

  • Thanks 1
Link to comment
Share on other sites

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 by CatPix
  • Like 1
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

If I'm to believe the monitor schematics :

pcw_monitor.gif

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

 

Eb3Yg0IX0AEkcTu?format=jpg&name=4096x409

 

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 by CatPix
Link to comment
Share on other sites

1 hour ago, CatPix said:

If I'm to believe the monitor schematics :

pcw_monitor.gif

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

 

Eb3Yg0IX0AEkcTu?format=jpg&name=4096x409

 

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. :)

Link to comment
Share on other sites

  • 7 months later...
  • 4 weeks later...
  • 1 year later...

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?

  • Like 1
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

I've progressed and found out the following is broken:

image.thumb.png.1f6574bcfece87c4379ad51c6c257638.png

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!

 

  • Like 1
Link to comment
Share on other sites

  • 3 months later...

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.

 

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...