Author Topic: Got amstrad pcw 8256 but the fun don't lasted very long ...... :O  (Read 14168 times)

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Offline JonB

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Seemingly, not. All the guys that could fix this are retired..


Meanwhile, the replacement turned up, but it, too, is dead. :(

Offline ||C|-|E||

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Here near London I know a company that could repair it, but they would be charging much more than the PCW is worth. That is why, at some point, I decided to start working in the monitors myself.  It was that and maybe a lack of common sense.

Offline Sebastian Blanco

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The fun is back and this time is not the Atari 2600  :P

















Offline JonB

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Nice one!


Hey, looks like you have an electrolytic cap for the chip smoothing. It doesn't really matter, but it's supposed to be a ceramic disc or tantalum cap.


Oh, also, I had an idea about how to resurrect these 9512s with monitor. Just need to examine the power board schematic. Don't throw any parts out yet!

Offline Sebastian Blanco

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Yes i used an electrolytic cap,  but if it can affect video quality i can change it.
I have to test it using scart later.
Also i read on your post that your tv image look white not green maybe your tv is not selecting RGB mode and you are just looking at composite video for that reason you don´t see the green rgb line video.
If you find how to fix the monitor it will be great, but i have lost all hope.

Offline JonB

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It's fine, I prefer white.


I think we can get the proper monitor running, but I need to do some experiments first. If I'm right, I will post instructions. Keep all the parts!

Offline JonB

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@Sebastian Blanco : It's looking more promising. After a quick look at the monitor schematic, I can see it is powered from the 12v rail only (with an additional 5v line to power a single IC that the video signals go through). In fact, they could be separate PCBs! So if we remove all the components in the lower part of the schematic and fit a 12v / 5v power supply, mounting it on the board where the removed components were, we should be able to resurrect the PCW 9512 monitor. Isolating the mains supply is easy because it passes through an easily recognisable choke called L001. On one side of this is the power supply, on the other is the mains input, switch and fuse. So if we take the choke out and wire its input connections directly to our new power supply, we will benefit from the PCW's power switch and internal fuse circuit. When the PCW is reassembled, it will look completely normal.


Note: There is no 24v supply in this scheme (for powering the printer) but it could be added if a suitable 3 way power supply can be found (24v / 12v / 5v). In terms of power requirements, I would say you need 3A for the 12v supply, 2A for the 5v and 2A for the 24v.

Offline Sebastian Blanco

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JonB look like a good idea to try, looking at the regulator part in the schematic, seem not be to hard to do, just drop a small 12v 5v inside the case (there plenty of space) and bingo  ;D .

Looking at the 8256 shematic i think the choke is L4001 here.
The 5v volt regulator as you say goes to the sync ic on the top seem to be the only one that take 5v.
What i don't get is the 5v line change to 12v adj half way and then change back to 5v again.




Offline JonB

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I meant to refer to L5001 which is the choke next to the power switch at the bottom left of the schematic.


The "12v adj" label is referring to the trimmer to the left of it. The line is 5v.

Anyway, all that old junk can be removed, so don't worry about it. But make sure the power cable that is plugged into to the main board is connected.

Oh, and the switched mode power supplies often have voltage trimmers on them, so I advise checking their outputs with a meter with a load, and adjusting where necessary.
« Last Edit: 19:06, 09 February 17 by JonB »

Offline Sebastian Blanco

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Hey man you are a damn genius it seems to work, i just bridged 12v and 5v and gnd to the main board from an ATX psu.
And the monitor glow i can hear it also, still dont rewired the motherboard to the monitor but look promising  :P
https://ibb.co/cwP61F
https://ibb.co/gKuaTv


« Last Edit: 03:05, 10 February 17 by Sebastian Blanco »

Offline JonB

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Hmm, yeah. I though it might. Well done!


Now why didn't I think to use one of my XT power supplies for a quick test? Too busy with uIDE, I suppose... Anyway, I have ordered a 5v 8A / 12v 3A supply from eBay so I will be hacking the monitor board soon.


Meanwhile, how about a better tube? http://www.cpcwiki.eu/forum/nc100-nc200-pcw-pda600/pcw-8256-white-screen/
« Last Edit: 09:50, 10 February 17 by JonB »

Offline JonB

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Right, then - let's give it a go!


I dismantled my machine and gave it all a good clean, including the CRT and boards. After the "massacre of the innocents" (removal of all High voltage parts of the circuit, as well as a bunch of other parts from the low voltage side), we have this:



* Power Connections.JPG
(1401.81 kB, 2592x1936 - viewed 285 times)



The space is for a drop-in 12v / 5v power supply which I have on order. The connections are as below - lft hand brown wire is 12v, right hand brown wire is 5v, blue wire is GND and the red jumper gets 12v to the CPU board's power cable to run the floppies.


 [ Invalid Attachment ]

Offline JonB

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Et voila!


 [ Invalid Attachment ]

Offline JonB

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There is still a problem though. The screen flickers on drive access. The monitor's 12v supply is connected directly to the motor power supply, maybe this is it. But the power supply has 8A. The 9512 supply is not the same as the 8256, see attached. The power lines are on sparate circuits. Maybe I took too much out. Or maybe I can fix it with a big smoothing capacitor. Any ideas?




9512 Power supply schematics:
* 9512 power RHS.JPG (137.24 kB - viewed 94 times)

 [ Invalid Attachment ]

Offline Sebastian Blanco

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You can try using a choke to filter the line that go the floppy drive.
Also a simple one is just to use a small separated 12v supply for the disk drive.
Or use a more modern floppy drives the 3.5 ones I'm using only use the 5v line no need for 12v.

Or use caps filters on the floppy motors:
https://www.pololu.com/docs/0J15/9
« Last Edit: 20:17, 10 February 17 by Sebastian Blanco »

Offline Sebastian Blanco

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Must say you removed all that components quite fast what do you used ?.

Offline JonB

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Desoldering station. This one:


http://www.ebay.co.uk/itm/172508276166

Offline Sebastian Blanco

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I have the cheaper version http://www.ebay.com/itm/30W-220V-Automatic-Electric-Suction-tin-Vacuum-Solder-Sucker-Desoldering-Pump-/271756761687?hash=item3f45f71a57:g:G44AAOSw-W5UyPqd
But have an eye on the bigger one like you got, much easier to clean that the self contained one.

Offline Sebastian Blanco

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its alive master its alive!

Offline Sebastian Blanco

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What i can confirm is the same issue on the 12v line, if you load from the disk drive the screen flicker a little.
After running the amperimeter on the 12v line the monitor only load 0.9 amp, and this power supply have like 20 amps on the 12v so no overload. Probably just noise from the floppy motor.
Also the monitor only load a few miliamps  on the 5v so no problem.
The digital motherboard use 0.8 amps 5v.

Offline JonB

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its alive master its alive!


EXCELLENT IGOR! NOW PASS ME THE ELECTRODES!!! MWAHAHAHAHAHAHAHAAAAA!

Offline JonB

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@Sebastian Blanco


While we're on the subject, what's that isometric game you are running? And isn't it time you cleaned it?  :D

Offline robcfg

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The game is La Abadía del Crimen (The Abbey of Crime), which @Habi ported from CPC to PCW.


It's the computer version of The Name of the Rose and a masterpiece of programming.


You should definitely check it, but it's though as hell, don't forget to get a guide  ;D

Offline Sebastian Blanco

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Hahahaha yes need a good clean, but first i like to get my messy workbench clean off all junk and finish the revival.
Also yes it is abadia del crimen, i don´t understand the game a monk get to me and start to talk and then i loose.
Still trying to fix the motor interference to the monitor ,the funny thing is that this disk drive is only +5 but it make the monitor flicker when it moves. Looks like it pull low the power line low or something.

Offline 1024MAK

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Try a filter, for example ceramic capacitor, high current inductor, and another ceramic capacitor.

Code: [Select]
                        L1
DC in ---------+-------mmmm-------+--------- out to device
               | C1               | C2
               =                  =
               | 220nF            | 220nF
0V in ---------+------------------+--------- 0V
Looking forward to summer in Somerset :-)