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Commodore monitor 1084S-P and PHILIPS CM8833II

i'm at work, but i'll grab a photo later, the heatsinks on mine are also conected to GND - there is a tiny spring clip that grabs them, which is soldered to the board.
 
heres the heatsink clip:
1709582869030.png

and heres where it goes on the board (for anyone interested :) ) oragne is where the tabs go, red is the 'pin' on the groupd clip (please don't look too closly at pin E just above, yes, I lifted a bit of the pad when initially de-soldering!)
1709583014517.png
 
I also found my 'scope , though it's not quite lab equipment, just one of the kits from amazon, but of course, I cannot find the probe lead.

1709583085505.png
 
spiny said:
heres the heatsink clip:
View attachment 1274931

and heres where it goes on the board (for anyone interested :) ) oragne is where the tabs go, red is the 'pin' on the groupd clip (please don't look too closly at pin E just above, yes, I lifted a bit of the pad when initially de-soldering!)
View attachment 1274932
Click to expand...
This Photos confirm a short from Collector and Base from heatsink if you use BU2508A without isolations, and probably is it damaged for this error, the EMITTER is coing to heatsink and COLLECTOR are shorted to EMITTER from heatsink.
 
demonlg said:
Sorry, from Collector and Emitter and not Base....my digit error....:)
Click to expand...

I need to learn not to rush in when replacing components :)

So, the BU508AF turned up today, is this part a suitable replacement ?

1709753644615.png

also got some freeze spray delivered today, I need to find a cap that takes a 'straw' as this just has the wide nozzle.

1709753719666.png
 
Hello,

Need help fixing my CM11342-05G having the following symptoms:

When turned on, the green light is on but the screen doesn't show anything and I can hear a squealing noise just for 1 sec and it is gone.
(not like when the flyback (LOPT) transformer is dead and it makes a continuous high pitch noise)

I checked all the rail voltages 128, 9, 5, 12, 28 and all are ok.
I checked R3563 and it is good reading 4.7 Ohm.

I noticed thought that the voltage across C2541 is zero while it should be -27V.
Also across R3534 it is zero while it should be -27V.

which component is the culprit ?

I would appreciate your help.

Thanks,

Shad
 

Attachments

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C2541 short circuit.
R3540 open circuit.
D6540 open circuit.
Transformer winding faulty (open or short circuit).

Something that -27V is connected to is short circuit.

Dave
 
daver2 said:
C2541 short circuit.
R3540 open circuit.
D6540 open circuit.
Transformer winding faulty (open or short circuit).

Something that -27V is connected to is short circuit.

Dave
Click to expand...

Hello Dave,

Which transformer you mean ? 5401, 5402 or 5510 ?

Thanks,

Shad
 
It doesn't say in your image.

The one that diode D6540 is connected to...

Between pins 9 and 10.

This is the source of AC Volts that is rectified and smoothed to derive the -21V DC supply.

However, if the transformer is not being driven properly, then this would be another cause of no supply.

Dave
 
Dave,
That transformer is the flyback LOPT 5510.
I have replaced it now and still nothing changed. 27V is not present.

Could the problem be coming from somewhere else that drives the flyback transformer ?
or shall try to replace D6540, C2540, R3540, R3541, C2541 ?


Thanks,

Shad
 
Why are you replacing stuff?

Why are you not using your multimeter to test things?

>>> Could the problem be coming from somewhere else that drives the flyback transformer ?

This is what I have already stated: "However, if the transformer is not being driven properly, then this would be another cause of no supply.".

Can you provide a link to the full schematic please?

Can I also suggest creating your own thread for this repair - otherwise we will get confused as to which monitor we are repairing...

Dave
 
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