Monitor Repair Tips

General notes.

Monitors which intermittently lose one or more colours etc. is often due to poor connections on the CRT base. If the rear cover has a big lump of sponge or spring fitted it presses the CRT PCB forward breaking the solder connection at the base connections. It means the metal screen has to be removed to view and gain access to the joints, but don't forget to test the cable too!.


Acer JD144F

Bright red screen with flyback lines. R944 (850R) bias resistor on crt panel. Replace with a (1k/ 7w) ceramic for longer life.

Goldstar 1725DM

Pink/blue screen. Re-solder video connector on the tube base panel that comes from the main chassis.

Mecer CM1402E

Powers up but shuts down immediately. IC402 (TDA1180) faulty.

Mitac/Escom AL4050PD

Dead. R940 (470k) oc.

Olivetti DSM 27-140E

This monitor was a bit of a pain, no line drive etc. etc. Anyway the cure is as follows...
With no line drive to the LOP transistor, I had to get the scope out. Checking around there was no drive to the line driver transistor. Tracing back the signal path I found the line driver chip. Again no signal from the chip, and no power to supply it. Checking the PSU all the voltages was present which made me think a little. Tracing the +12v I found a diode which feed the line stage with 12 volts on one side and zero on the other. Checking it with my meter it read ok. I started to remove parts after the diode to see if anything was dragging it down. I could not find anything. So as a long shot I changed the diode.

The next thing it starts into life. The diode is a 1N4818. Sorry I can't give you a circuit reference but its now Sunday and the monitor when back on Friday. It goes to show a 5 pence diode can stop a something from working.

Targa M142PNL

Dead. Lopt tranistor o/c b-e. Original is 2SC4769. Used BU508DF.

Trust 14" CM2228NL

Dead. R804 (27k/ 2w) oc.

Viewsonic 14ES Mod/no 1448ESI

Dead. R603 (33k) oc.