Author Topic: Ctm644 Vr402 pot replacement  (Read 964 times)

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Offline JohneBravo619

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Ctm644 Vr402 pot replacement
« on: 16:01, 24 February 21 »
Hi


I have been having a lot of trouble with brightness on my Ctm644 monitor. On opening it up it looks as though the sub bright pot has been damaged.


Is there any particular replacement for this?


Also, I can discharge the anode but is there any particular caps that still hold a charge?


Thanks


John

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #1 on: 16:14, 24 February 21 »
Hi


I have been having a lot of trouble with brightness on my Ctm644 monitor. On opening it up it looks as though the sub bright pot has been damaged.


Is there any particular replacement for this?


Also, I can discharge the anode but is there any particular caps that still hold a charge?


Thanks


John

It's a standard 5K Linear trimmer pot. You should be able to find them at any electronics supplier, but they look completely different these days. They are closed blue boxes instead of an open design.
There are a few larger caps on the PCB that I would check that they are discharged before poking around.

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #2 on: 16:17, 24 February 21 »
Thanks Bryce! Will take a look!

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #3 on: 17:28, 24 February 21 »
Would you possibly have a list of the capacitors that normally need replacing... May as well give it a full service while I'm there... 😁

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #4 on: 09:58, 25 February 21 »
I don't have a list, but if you want to start swapping capacitors, it's the larger electrolytic capacitors that would most likely need to be changed.

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #5 on: 10:56, 25 February 21 »
Found the list. Thanks again Bryce!!


Thanks

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #6 on: 13:39, 16 March 21 »
Back again... So.... Replaced the trim pot.. Got nothing... Tried to adjust it but think there is something else causing it not to work. Screen still has static and makes a noise to know its on. I then stupidly knocked the h hold trim pot while looking around....turned it on without knowing and now it does not come on at all. Anyone know which capacitors/resistors would have been affected if the h hold trim pot was not properly connected?
Thanks

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #7 on: 15:00, 16 March 21 »
None. I think you may have a problem with the LOPT.

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #8 on: 16:44, 17 March 21 »
So you think that with damage to the h hold pot the LOPT was affected? It was giving a static feel to the screen before this happened...

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #9 on: 16:51, 17 March 21 »
So you think that with damage to the h hold pot the LOPT was affected? It was giving a static feel to the screen before this happened...

No, I think the LOPT has died of it's own accord, unrelated to the Pot. Is it still producing static charge?

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #10 on: 16:53, 17 March 21 »
No....seems dead...no static or sound. Any ideas on where i can get a replacement Bryce?..... don't want to get rid of this monitor... :(


Thanks for all your help!

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #11 on: 17:14, 17 March 21 »
From another CPC monitor. I don't know of anyone selling this part.

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #12 on: 19:05, 17 March 21 »
Bryce...silly question....but would a ctm644 mk1 flyback be the same as the one in the mk2 ?

Offline Bryce

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Re: Ctm644 Vr402 pot replacement
« Reply #13 on: 19:33, 17 March 21 »
I think so, but I'm not 100% sure.

Bryce.

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #14 on: 21:36, 17 March 21 »
Thanks Bryce. Not sure if anyone else knows but i have model 3714009 and i have an offer for a 3714016. Anyone know if this is compatible? Maybe just a newer model??

Offline JohneBravo619

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Re: Ctm644 Vr402 pot replacement
« Reply #15 on: 21:46, 17 March 21 »
Bought it anyway....It was new on ebay from someone who bought them for their business monitors back in the day. Fingers crossed.