pcw wont start anymore

Started by radu14m, 15:21, 16 September 18

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sad day. :doh:
today my pcw did not start anymore - no sound, no screen display - nothing - completely dead.
yesterday, everything runs perfect. :picard:
what can be the problem ?

i open it and check the fuse, it's fine.
As i am a noob in electronics, i appreciate any advice :)

thanks !!!



There have been discussions about such failures, you might look for these on this site.

The power supply is certainly understood to be fragile, and not easy to repair if certain parts go.   Usually, this sort of failure is readily visible due to burn marks, or smell.

You might take a couple of pics of the area of the board (both sides) near to the mains inlet.   Someone might spot components that look visibly unhealthy!

There may well be a service manual (it's not too big, there's not THAT much in the box) on the web.

Oh, do you have anything attached to the expansion interface, that might have moved?   Remove it, and try again.



There is a schematic at least.

I had the same thing happen to my 9512. In the end I ripped the guts out of the power supply and fitted a compact switching PSU.

Not for the inexperienced though. There are hairy voltages in there.

I also had just the board & drives running off a small 5v/12v PSU with the uIDE expansion port "video" on an LCD display (you can see it in one of the uIDE demo videos I posted on youToob).


You can find the service manuals on the PCWWiki.

As JonB said, don't play with the PSU board. Try to check voltages on the connector that goes to the main board.


thanks Guys, i had an cps8256 attached.
i removed but no go.

also nothing smells, or looks burnout.
i am very carefully because of high voltage.
ill post some pictures :)


Hmm, I'm not at all sure about this, but I think that my PCW has some sort of thermal cutout.   If something happens, it will cutout.   Then, after a number (?) of minutes, it will work again, assuming the problem (like an expansion unit re-seated) it will work again.

But now I think about it, this may NOT be original?   Long ago, late 1980s maybe, my PCW went bang when I tried to daisy-chain two things on the expansion interface, and clearly something shorted.   I took the system to a repair shop, and they fixed it.   Maybe they did an official (or semi-official ?) upgrade?   Since then, I have had a couple of problems that caused the system to NOT work, but after a delay, everything was OK again.

Anyone heard of anything like this before??

Oh, the CPS8256 should NOT be a problem, the way it fits on it's pretty much impossible to short anything.  I tried to attach something else that had a pass-thru, with the CPS on the pass-thru, and clearly that was NOT as foolproof!



Quick explanation: The PCW uses an AN6531 linear regulator to produce the 5V rail. The AN can actually only supply 500mA, but the designers added a few transistors (Q5002 and Q5005) so that it can actually supply a lot more. This regulator has both thermal and current overload protection. So if you pull too many amps from the 5V rail, the regulator will shutdown. However, both the thermal and current protection reset as soon as they have cooled down and it will start supplying 5V again (assuming you have removed the problem that was causing the overload).

So this isn't something the repair guy added, it was there all along. The CPC (actually the CPC monitors to be exact) do exactly the same thing, but they used an L78MG regulator with a current amplifier / bypass using just one transistor.

This doesn't mean they are indestructable though. A complete short or regular overloads can still cause the regulator to give up permanently.


Sebastian Blanco


wow, thanks !!!
to connect a ATX power supply was also one of my toughs  ;D
can you make please some more detailed pictures, to see how did you connect everything ?


Hi Radu

I'm not sure if I'm comfortable advising you regarding your PCW. The reason is that to be able to keep the screen and CPU working as they were before it failed, you will need to make modifications to the power board. You have said that you're not familiar with electronics, and so I am concerned that if I do try to explain this, there are big voltages in there and you could get hurt.

Also, I did succeed in restoring my 9512 but it is not the same as your machine. They are similar, but not identical, so the pictures in my thread might not help. I don't have my PCW apart at the moment so I can't post any more photos. I am sure I could get it going myself if I had it in front of me, but I don't think I can do it remotely, as it were.

Another worry is that, so far, we have been assuming it is the PSU that has failed, but it might be something else. If you rip out the guts of the PSU and it still does not work, then you are in a worse place. It might prove easier and cheaper to buy another machine. They're not expensive (at least in the UK they are cheap). If your PSU is OK, it may still power the CRT. Plug the machine in and look inside the back of the case - can you see an orange glow from the tube heater filament?

One easier and safer alternative would be to connect a hard disk PSU (sort of thing you see on eBay - +12v and +5v) to the main board (where the cpu is) and test that. You can use a uIDE PCW expansion port adapter (the one with the video output) to get the image on a TV. Then at least you would be up and running again (assuming your main board is OK). Actually you could see if it worked just by powering the board - if it boots you can see the floppy drive come on, seek and go off again. Then if you do "DIR" on the keyboard it should move again. If this test is OK you can move on to getting a screen up with the adapter.

An ATX PSU is not as safe an option as a small HDD PSU because it is capable of putting out so many amps. But if you have one to hand then try it. Just be sure to connect it up right...

Good luck


Thanks JonB for the explanations, and i appreciate your concerning.

I am not so familiar with electronics, but did some soldering and montages in the faculty as engineer.
I would test the PSU and post some fotos, also to see the boards and components.

now im not at home, and can do the tests only in the weekend.
i want to keep the machine as it is, with the green screen as it reminds me of years when i start working with the pc :)

can you post please the link with the [size=0px]uIDE PCW expansion port adapter you mentioned ?[/size]

Sebastian Blanco

The adapter is sold by JonB you can see it in action on this thread:Is part of the IDE kit.


thanks, it"s an amazing kit :)


So.. some information on the power & video connectors inside the PCW8000 series machines.

Drive power connector:
Red - 12v
Black - GND
Orange - 5v

Note: 12v and 5v are the wrong way round for a normal 3.5" drive.

CPU Power connector:
Brown - GND
Black - GND
Red - 5v (for CPU and drive electronics)
Orange - 12v (for drive motors)
Yellow - 24v (for printer)

Video connector:
Brown - NSYNC
Black - GND
Orange - Video
Yellow - GND

You can disconnect the main power socket from the board and use the auxiliary drive connector cable to supply +5v, +12v and 0v (GND) to the mainboard alone, without connecting the machine to the mains. Use a small power supply like you find on ebay for powering external HDDs. Just be aware that 12v and 5v lines on the PCW drive connector are not the normal way round for a disk drive, so make sure when connecting 12v that it's going to the red wire, and 5v to the orange wire.

You can build a small circuit to mix the video and NSYNC signals from the video connector using stripboard. The schematic is shown in the last picture.




Hey Radu, you're in luck.

I have already sent the video PCB off to the fabricators. As you can see from the picture, it is tiny - it measures 21mm x 29mm. Takes 2-8 weeks to be delivered. I designed it so that it will plug straight into the video output header on the PCW's main board (the one at the back which is coloured blue, labelled CP103). I have a suitable female pin header to hand which will be ideal for this. You will need to connect +5v to it though - you can get this from the auxiliary drive connector or from your +5v PSU line. There is also a +5v line on the adjacent keyboard connector (CP103), it is the red wire (pin 2) so if you can solder a wire to that you should be good. In fact this is the best place to get 5v from as it is next to the video connector. The board's composite video output is by way of header pins (same as the uIDE expansion port connector) so you will still need to make a cable up. I might be able to help you there.


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looking great, thanks !
one ideea would be to remove later the CRT from the PCW an switch with an LCD.
of course in the PCW case 8)


You'd need to find a 12 inch 4:3 ratio monitor... let me know if you do.


Radu, the boards are in the post. 2-8 weeks delivery.. :(


I've just acquired a couple of 50 way edge connectors... so I can build you an adapter with video for the uIDE...  ;)



Radu, the prices are all shown on the uIDE wiki page. As the Pound is nearly worthless the price to you (in a different currency) has, in effect, gone down. You keep winking at me - have you got something stuck in your eye?  :D

For the tiny video mixer board, I won't ask for much, but I haven't worked out how much it will cost to build yet. The PCBs are still on the slow boat from China..

In the meantime, have you got yourself a 12v / 5v PSU yet, and if so, have you connected it to the processor board to see if there is any activity on Drive A? If it's all good, it should boot up. You won't see anything on-screen, of course, but you will see and hear the disk loading CP/M into the processor board's memory.


Radu, the boards arrived. They are tiny, smaller than an SD card..

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The fabricators made a mistake with the silkscreen (hence these curved lines going across the board) but otherwise it should be OK.

Do you want me to go ahead and make one or would you prefer to have the uIDE + video output?


Top of board:

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Rear of board:

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The 4 pin plug should just fit into the PCW's video socket although I haven't tried it yet.


wow, looks amazing !!!!
great work !what is the cost for such a tiny video board adapter ?
i test my pcw with an external psu, it"s alive  :)

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