Need felp fixing Sony CRT monitor (strange smell)

[gmipf]

Model: Sony CPD-G420 (without LCC board)

Service manual: https://drive.google.com/file/d/1wAzhS2 ... drive_link

Back story:
I used the monitor for about 1 year daily as a second PC display and sometimes for 15khz gaming through an OSSC. From one day to another the monitor stopped operating.

The failure code was:

Code: Select all

  Amber   →    Off   →  Amber   →    Off
(0.25 sec) (0.25 sec) (0.25 sec) (1.25 sec)

The failure description is "HV failure" according to the service manual.

My first step was, also I assume a classic beginner mistake. I done a complete electrolytic capacitor replacement of the A1 and D board. Of course that did nothing.

Then I started measuring resistors and diodes and found a defective resistor (R903) which seems to be part of the "HV Protector Circuit Check" according to the service manual.

Current problem:
After replacing smd resistor R903 the monitor is turning on again but now there is a strange smell, when I turn the monitor on for about 10 minutes the whole living room smells. The smell is not quiet like burnt and there is no black smoke.

When I turn on the monitor while the cable between the A1 board and the neck board is disconnected, the smell goes away. I also got an HV probe, I measured 27kV as recommended in the service manual.

That smell was definitely not there before the monitor stopped working. Is that smell related to the neck board or the deflection yoke? I don't know what to do next.

[Josh128]

If you have HV present at the anode, it could be a shorted horizontal output transistor. That can make things hot quick and also kill parts in the power supply section. Are your cathode / electron gun heating filaments glowing in a dark room when you power on?

Check to make sure you still have signal driving the neck board as well. If you get a cheap inductance tester, you can check your H and V deflection coils to see if they read to spec, if you can find it. You should be able to touch the coils on the yoke when its powered on to feel if its getting super hot. If so, could well be a shorted HOT.

[tongshadow]

Are you even getting a picture?

[gmipf]

If you have HV present at the anode, it could be a shorted horizontal output transistor. That can make things hot quick and also kill parts in the power supply section. Are your cathode / electron gun heating filaments glowing in a dark room when you power on?

Check to make sure you still have signal driving the neck board as well. If you get a cheap inductance tester, you can check your H and V deflection coils to see if they read to spec, if you can find it. You should be able to touch the coils on the yoke when its powered on to feel if its getting super hot. If so, could well be a shorted HOT.

Sorry for the late answer. I forgot to mention that I also get a picture when everything is connected. Could the horizontal output transistor still be shorted?

[Josh128]

If you have HV present at the anode, it could be a shorted horizontal output transistor. That can make things hot quick and also kill parts in the power supply section. Are your cathode / electron gun heating filaments glowing in a dark room when you power on?

Check to make sure you still have signal driving the neck board as well. If you get a cheap inductance tester, you can check your H and V deflection coils to see if they read to spec, if you can find it. You should be able to touch the coils on the yoke when its powered on to feel if its getting super hot. If so, could well be a shorted HOT.

Sorry for the late answer. I forgot to mention that I also get a picture when everything is connected. Could the horizontal output transistor still be shorted?

Not if you have a picture. Shorted HOT should be no picture or just a bright vertical line or dot in center of picture.