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General Category => Technical Support - General => Topic started by: Chipmop on 21:59, 18 March 21

Title: CTM644 without 5VDC and 12VDC output
Post by: Chipmop on 21:59, 18 March 21
Hello together,
I've searched a long time to find such a forum.
Sorry for my bad english, I give my best.
I call a "Schneider CPC 6128" with a CTM644 my own, I bought it 36 years ago ;D
Recently it stops working.
I searched of course in the forum but found no solution for my problem.
I describe as good as I can:
The screen crackles when switch on and when switch off there's a short lightning at the screen.
I measured no voltage at 12V and 5V output. I replaced a lot of passive parts but has no improvment at all. For save I changed the STK7308 to a new one, but still nothing happened. I measured at the output winding of T501(8142009) for the 12V regulator, but there's also no voltage. To besure that the 12V regulator is not shortened I removed it, but still no output at the output winding. I measure around 1MOhm at these output pins. Maybe the transformer T501 is defective? Now I'm at loss and hope somebody can help me.


Thank you in advance!
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Animalgril987 on 01:46, 19 March 21
Hi Chipmop.
Welcome to the forum  :D


I'm not an expert on monitors, but there are people on here, that I'm sure will be willing and able to help.


Regards,


Alan.
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Chipmop on 19:18, 19 March 21
Thanks Alan, you give me hope 8) 
It would be a pity if the device couldn't be repaired.


best regards.


Armin

Title: Re: CTM644 without 5VDC and 12VDC output
Post by: villain on 20:28, 19 March 21
Hi. Armin sounds quite german. Just wait for @Bryce (https://www.cpcwiki.eu/forum/index.php?action=profile;u=225) joining this thread...  :)
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Bryce on 20:32, 19 March 21
I'd consider getting an external PSU and a SCART cable to use the CPC on a standard TV. The monitor might be savable, but is it worth the bother if you can continue gaming / programming on a TV you already have?

Bryce.
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Animalgril987 on 21:04, 19 March 21
@villain (https://www.cpcwiki.eu/forum/index.php?action=profile;u=210): you called, and he appeared... :D
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: xesrjb on 21:23, 19 March 21
Have a look here,




https://www.forum64.de/index.php?thread/92459-anschluss-cpc-464-an-pc-monitor-mittels-konverter/


A very good alternativ..


You can PM me in german, if you have any questions..


xesrjb
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: villain on 21:35, 19 March 21
Quote from: Animalgril987 on 21:04, 19 March 21
@villain (https://www.cpcwiki.eu/forum/index.php?action=profile;u=210): you called, and he appeared... :D


That's what I expected. 😀 Wish this would work as good in other cases. 😁
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Chipmop on 21:53, 19 March 21
Such a converter could be an alternative, yes. I apprecita your suggestion, but I won't give up that quickly. And I like this retro monitor, it just belongs to this old computer. So I the converter will be my last emergency nail  :D
I go on searching for the issue, i suspect the problem in the area of the transformer T501 or the transformer itself.
I will keep you up to date if i have new knowlege.


@villain:with German your absolutely right ;)
[/size]
[/size]Armin
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Bryce on 11:10, 20 March 21
Quote from: villain on 21:35, 19 March 21

That's what I expected. 😀 Wish this would work as good in other cases. 😁

I just happened to be passing by :)

Bryce.
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Chipmop on 15:44, 21 March 21

Hello together again,
i fixed already one problem.The output winding of the 12V output section was actually oxidized near the connection pin. I was able to repair this, because the wire of the transformator output winding was long enough.  Now output of 12V and 5V is present and the cpc seems to start.
But the joy was not so great, because the next problem occurred right away.
It seems that the veritcal deflection is also defect somewhere.


Armin
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Bryce on 17:19, 21 March 21
It must have been stored in very bad conditions for that to happen. If that rusted through, then you're going to have many more parts that have failed or are about to fail.

Bryce.
Title: Re: CTM644 without 5VDC and 12VDC output
Post by: Chipmop on 21:22, 21 March 21

Quote
It must have been stored in very bad conditions for that to happen. If that rusted through, then you're going to have many more parts that have failed or are about to fail.
That's really not the case. It was stored always in dry area.


But in the meantime my CPC is back. The vertical deflection problem was my fault. I accidentally switched SW401 to GND :doh:
Only the colors should be better adjusted.


Thanks for your comments


Armin
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