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General Category => Technical support - Hardware related => Topic started by: Targhan on 21:42, 04 September 23

Title: CTM 644 with strange RGB desync
Post by: Targhan on 21:42, 04 September 23
Sorry if this problem has been talked about a zillion times, but my faithful CTM644 has some strange display problem, as you can see...

(https://www.julien-nevo.com/cpcScreen.jpg)

I heard a "tac" sound then, the screen became "ok", then a few minutes later, another sound, and it went dark. I dare not turn it on again for fear to make the matter worse.

Is it something that can be repaired easily? There is a meeting in October in France, is it something that can be repaired there by skilled CPCists?

Thanks!
Title: Re: CTM 644 with strange RGB desync
Post by: Targhan on 21:45, 04 September 23
@Kris Maybe that's something you know about?
Title: Re: CTM 644 with strange RGB desync
Post by: pelrun on 06:00, 05 September 23
The coils in your deflection yoke have shorted. It's shown up here a few times before:


https://www.cpcwiki.eu/forum/hardware-related/problem-with-a-ctm644-monitor/
https://www.cpcwiki.eu/forum/hardware-related/another-dodgy-monitor-ctm-644/
https://www.cpcwiki.eu/forum/technical-support/i-burned-the-ctm-644-accidentally/

One of those was repairable! But the fact that your screen has gone dark since means there's probably been more damage done elsewhere.
Title: Re: CTM 644 with strange RGB desync
Post by: Kris on 06:54, 05 September 23
As Pelrun said, the Yoke is shorted (damaged) but several other components as well...
Keep it for the meeting, I will check if I have a "full tube" available.
Title: Re: CTM 644 with strange RGB desync
Post by: Bryce on 12:12, 05 September 23
I wouldn't be so sure that the coils are damaged. A few dodgy capacitors and failed transistors could cause this too, even without the coils being bad.

Bryce.
Title: Re: CTM 644 with strange RGB desync
Post by: Targhan on 23:17, 05 September 23
Thanks for your replies!

@Kris Do you need me to buy some hardware "thingy" before the meeting?
Title: Re: CTM 644 with strange RGB desync
Post by: Kris on 06:35, 06 September 23
Quote from: Targhan on 23:17, 05 September 23Thanks for your replies!

@Kris Do you need me to buy some hardware "thingy" before the meeting?

Nope, wait untill we can do the diagnostic. 
Title: Re: CTM 644 with strange RGB desync
Post by: HAL6128 on 08:53, 06 September 23
Looks like a nice demo effect. 
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