Author Topic: Focus adjustment for a PCW8256 screen?  (Read 4956 times)

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Offline JonB

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Focus adjustment for a PCW8256 screen?
« on: 15:09, 31 December 13 »
Hi

Is there a focus adjuster for the PCW8256 monitor on the main board somewhere? Mine a re a little blurry and I'd like to see if they can be improved.

Thanks

JonB

Offline Bryce

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Re: Focus adjustment for a PCW8256 screen?
« Reply #1 on: 16:27, 31 December 13 »
CRTs are focused with a knob that's directly on the flyback transformer. That's the big black plastic thing with the fat lead that goes to the side of the tube. WARNING!!!! Disclaimer, you do this at your own risk. This is the most dangerous part of the CRT and contains really scary voltages that will fry you to a crisp! DO NOT REMOVE THE FAT LEAD UNDER ANY CIRCUMSTANCES AND AVOID TOUCHING ANYTHING ON THE CRT PCB OR THE NECK OF THE CRT BECAUSE IT WILL PROBABLY KILL YOU! Even when the CRT is turned off and unplugged! Ok, so if you still want to try it...

The flyback transformer usually has two adjustments and the focus is usually the top one of the two knobs and looks something like this: http://www.esorensen.com/wp-content/uploads/2008/12/img_6199_1.jpg (The two knobs can be seen on the right hand side in this picture). You'll need to turn on the PCW and leave it a few minutes to warm up. Now use a long insulated screwdriver to slowly turn the knob. The knob will probably be a bit stiff and difficult to turn at first, but after it loosens up you should be able to finely adjust the focus. When it looks good, turn off the PCW, close the case back up and leave it for a while to cool down, then turn it back on and check that the focus has stayed.

Try not to kill yourself.

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Offline CanonMan

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Re: Focus adjustment for a PCW8256 screen?
« Reply #2 on: 17:14, 31 December 13 »
Unfortunately, the 8256/8512 monitor chassis doesn't have a focus control at all, either on the board or on the line output transformer.


Poor focus may be caused by some of the high-value high-wattage resistors on the CRT base board or main board drifting out of tolerance, from what I can see on the schematic. I've owned a few PCWs though, and a couple had slightly soft focus. I never actually got round to curing them before selling them on though  :laugh:

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #3 on: 19:49, 31 December 13 »
Thanks Bryce. I did look for some adjustment on the FBT but couldn't see any. I think I'll live with it... Unless anyone knows a particular component that is prone to causing this.

Regards

JonB

Offline Gryzor

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Re: Focus adjustment for a PCW8256 screen?
« Reply #4 on: 20:55, 31 December 13 »
Phew, Jon posted back :D

Offline Bryce

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Re: Focus adjustment for a PCW8256 screen?
« Reply #5 on: 14:13, 01 January 14 »
Hmmm, if the Flyback transformer doesn't have any adjustments, then it'S usually done with a mechanical adjustment on the neck of the tube, but I haven't a clue how to do it, it's different on every tube and I though they'd given up using that method when black and white TVs went out of fashion.

Good to see you survived though :) Welcome to 2014 :)

Bryce.

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #6 on: 10:42, 02 January 14 »
Yeah, I LIVE! Mwahahahahahahhh!

I don't recall seeing any mechanical adjusters on the back of the tube by the way. Hmm, at this rate I'll be swapping the 8512's tube and board out for the one in my 8256 (which has a better image).

:)

Offline MaV

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Re: Focus adjustment for a PCW8256 screen?
« Reply #7 on: 14:07, 02 January 14 »
Why not just swap the boards instead of the tubes? That should be a bit less dangerous. (provided of course that the 8512 and 8256 have the same size and connectors, I don't own a 8512).

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Offline TFM

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Re: Focus adjustment for a PCW8256 screen?
« Reply #8 on: 18:23, 02 January 14 »
Or just move some RAM chips....  :)
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Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #9 on: 20:03, 02 January 14 »
Or just move some RAM chips....  :)

...and Drive B: which entails destructive case mods to the 8256, which I am definitely not doing (even though I prefer the cream case to the grey case). Removing the tube entails taking the HT lead off, and this didn't seem too easy last time I tried.

I did find a pair of rings on the yoke that, when adjusted (very carefully) seemed to alter the position if the image. No effect on focus, though.

Offline Bryce

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Re: Focus adjustment for a PCW8256 screen?
« Reply #10 on: 23:14, 02 January 14 »
The adjustments that go around the tube neck are to adjust the pictures angle/orientation. The focus (if done like B&W TVs were) will be a forward/backwards slider adjusted with a screw like this: http://www.oldtellys.co.uk/tubeneck2.jpg The screw moves a metal rod that effects the focus grid inside the tube.[nb]Shit, I'm really starting to show my age at this stage :D[/nb]

Bryce.

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #11 on: 13:03, 04 January 14 »
Thanks, Bryce. Where did you dig that up from? ;)

Anyway, from memory, I don't think I saw an adjuster like that. It's most odd! Could this be the famous "Amstrad price cutting" in action, I wonder?

Offline Bryce

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Re: Focus adjustment for a PCW8256 screen?
« Reply #12 on: 15:46, 04 January 14 »
The picture was just one I found on the internet. The information comes from my very early days of electronic repair. Yes, there were still black and white TVs in use when I started messing about with electronics. My first lessons (from my father) included valve theory too! :D

No matter how much Amstrad was trying to save, there must be some way of adjusting the focus. It can't be left out completely.

Bryce.

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #13 on: 19:31, 04 January 14 »
Yeah, I agree. Just cannot see anything, either on the yoke or power board; although the yoke is slideable on the stem (or appears to be), the damned thing is glued into place. My bet is they focus at the factory then apply an enormous blob of glue to each side to hold it in place.


In the end, I swapped the screen / power board assemblies round, so I have a PCW8256 with a slightly softer picture, and a PCW8512 with a slightly sharper picture. There's not that much difference, but it's enough for me to notice (therefore, enough for me to be irritated by it).


All I have to do now is find a new home for this 8256 (with working printer). Anyone...?

Offline robcfg

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Re: Focus adjustment for a PCW8256 screen?
« Reply #14 on: 19:47, 04 January 14 »
Hey Jon,


Would you be so kind of telling us both boards MCxxx code?


If we haven't them scanned already, would it be possible that you send me 300dpi scans of both sides of both boards?


Thank you very much!

Offline MaV

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Re: Focus adjustment for a PCW8256 screen?
« Reply #15 on: 21:01, 04 January 14 »
@JonB: Good Job! I wouldn't dare doing that. Now, about the blur. Does it occur evenly on the whole screen area? One PCW here shows an uneven blur, i.e. it's a bit blurry in some places and in others look sharper. The difference is not that big, but noticeable when having a close look.

@robcfg: That reminds me to make pictures of mine if they differ from those of the PCW wiki ...
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Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #16 on: 11:24, 05 January 14 »
Sorry, do you mean the processor boards of both machines, or the processor and power boards of the 8512?

Offline robcfg

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Re: Focus adjustment for a PCW8256 screen?
« Reply #17 on: 15:19, 05 January 14 »
The processor boards of both machines.


Here you can find the models we already have.


Thanks, mate!

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #18 on: 19:40, 05 January 14 »
I also have an AMX Mouse with interface..

Offline robcfg

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Re: Focus adjustment for a PCW8256 screen?
« Reply #19 on: 19:56, 05 January 14 »
If you can take some pictures/scans of the AMX mouse and interface, that would be vey nice!


Can you create disk images of the software?

Offline JonB

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Re: Focus adjustment for a PCW8256 screen?
« Reply #20 on: 22:55, 06 January 14 »
There wasn't any software. The previous owner destroyed all the disks because it belonged to her husband and she was trying to preserve his privacy. So she zapped it all, including the system disks. However, the AMX software is online because I found it and tried it out. It's called AMX Desk, and it us a very primitive desktop wrapper for CP/M. Sadly SymbOS doesn't support the AMX mouse.

Offline TFM

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Re: Focus adjustment for a PCW8256 screen?
« Reply #21 on: 04:56, 07 January 14 »
Then use the AMX mouse in the joystick mode... or use FutureOS  ;)   :laugh:  [nb]Couldn't resist.[/nb]
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Offline Munchausen

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Re: Focus adjustment for a PCW8256 screen?
« Reply #22 on: 19:09, 07 January 14 »
TFM - is there FutureOS for PCW? I've never seen it.


Also, I don't think you can put the mouse into joystick mode? (I have one, if you can I didn't know...)


But you're joking, right?

Offline TFM

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Re: Focus adjustment for a PCW8256 screen?
« Reply #23 on: 21:32, 07 January 14 »
Ok, the truth is out: You need a CPC and on CPC the AMX mouse can be set into joystick mode by holding one button for 5 seconds while switching the power on. Maybe it also works for Joyce.  :)
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Offline Bryce

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Re: Focus adjustment for a PCW8256 screen?
« Reply #24 on: 21:51, 07 January 14 »
Ok, the truth is out: You need a CPC and on CPC the AMX mouse can be set into joystick mode by holding one button for 5 seconds while switching the power on. Maybe it also works for Joyce.  :)

The AMX mouse is a passive device with no ┬ÁP or anything intelligent inside. Holding any of the buttons down for any amount of time when you turn on the CPC will do diddly-squat other than give you a row of X, Z or whatever on the screen :D

Bryce.