monitor shutdown

hi there again!

I am repairing an old monitor (I was not able to get the serial). But its oldy im sure. During power on, i feel a static at the front of the monitor. An indication of a high voltage but after a few minutes, 4 minutes i think, it suddenly shutdown. So I used my multimeter and tested the collector of HOT. I measured a voltage but when the monitor dies up, the voltage also disappears. I changed some bulging capacitors but still the problem persists.I suspect the deflection yoke but I have no yoke tester. I heard that running a monitor without deflection yoke disconnected is not good. I am a little bit lost here because I havent practiced it for long time now. So can anybody give me suggestions on how to fix this problem. I know safety precautions in electronics. I want friendly advise please. Thanks in advance.

I would doubt the deflection yoke to be bad.

Use an ESR meter, and check all the caps in the scan and power supply sections. It is impossible to tell visually if a cap is electrically bad, unless it had physical damage.

A common cause of a start-up, and shut down, is that there is a fault in the high voltage regulator, any part of the power supply, or there is a scan failure due to failed components.

The only way you will be able to fix this monitor is with proper troubleshooting. This would take a good knowledge of electronics, experience in monitor servicing, and the proper tools to do the work.

I would suggest you give the monitor out for an estimate. This way, you can make an intelligent decision to know if it is worth to service, or simply replace it. Also, when working in TV monitors, there are serious safety issues to be considered.

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Jerry G. ======

I am repairing an old monitor (I was not able to get the serial). But its oldy im sure. During power on, i feel a static at the front of the monitor. An indication of a high voltage but after a few minutes, 4 minutes i think, it suddenly shutdown. So I used my multimeter and tested the collector of HOT. I measured a voltage but when the monitor dies up, the voltage also disappears. I changed some bulging capacitors but still the problem persists.I suspect the deflection yoke but I have no yoke tester. I heard that running a monitor without deflection yoke disconnected is not good. I am a little bit lost here because I havent practiced it for long time now. So can anybody give me suggestions on how to fix this problem. I know safety precautions in electronics. I want friendly advise please. Thanks in advance.

Hi!

Do you have a picture during this time? I suspect you don't. Are the CRT filaments lit?

1. NEVER Measure the HOT collector voltage with the deflection working! You may, if you own a good old VOM with a 1500V (or greater) scale, and ONLY IN THIS SCALE!
2. If the voltage disappears it is either a power supply problem or the controller is shutting down sensing some other fault. Can you turn the set back on with the power switch? do you need to press once or twice? I think, there is some other problem causing the micro to blank the video and to shutdown. Maybe vertical deflection: Turn op the SCREEN Control on the flyback (with the set on and the deflection running) and see if you get a raster or a horizontal line. The H-yoke is very unlikely at fault, the V-yoke is possible (in theory) but I've never heard of a V-yoke failure. It would suspect the Vertical output stages then (or a service switch)