Diagnostic old CRT monitor

Thread Starter


Joined May 28, 2011
I have to repair an old CRT monitor used for a PC. The motherboard had one damaged capactior 400 volts and 150 uF (microfarads) (the top of the cap was bend a little but there was no stain on it) and I replaced it with a new capacitor but that didn't helped or changed anything.
Usually when you turn on an old WORKING CRT monitors you hear one single click. The problem with this one is the usual clicking sound is constant for around 20 seconds like it is turning on and shutting down. There are two different clicks occuring and simply repeating. One is louder than the other. It doesn't show a picture even for a split second. The power led is green all the time but no picture at all. It is not a problem related to the power button. I already disassembled the monitor and the button is fine and making contact. All the other capacitors looked fine and there where no burned elements or cold solders.
This click is not a high frequency click because some old CRT does make high frequency clicks. I would rate it a first octave click :D in the range of maybe 300-500 MHz. Even if the repair is expensive I would like to know what is causing this sound?