LC 12" RGB Display (M1296x)

[flakes]

Hi all

New to the forum, I am having a task trying to restore a 12" RGB for my LC. I have fully recapped it but still not getting a display. I don't currently have a HV probe so cant test the HT but the display is currently acting like the one shown here:

https://youtu.be/IqK6KyChlpg?t=1719

Not sure where to go from here... 

 

[techknight]

Ok, so this is happening when the electron gun is being driven hard into saturation. Way harder than it should be. There should be a negative voltage that biases the CRT beam current into cutoff, with the video amplifier driver transistor array driving the beam back into the active region. 

This is either the video amplifier IC that has failed, or, the G2 screen drive is way too high. May need to turn that down a bit to see if the picture comes back. That adjustment is on the flyback transformer. 

If that doesnt work, then there is a voltage missing somewhere, or the video amplifier IC has failed. 

 

[flakes]

Hi

Thnaks for the tips. I will have a look in a day or so. I have managed to get a 40KV probe kit so will be able to check all voltages and see whats wrong.

Dan

 

[Scott Baret]

If you swapped anything, be sure you swapped model for model. There are two revisions to this monitor, which involve a 100V difference.

 

[flakes]

I haven't swapped anything. I am leaning towards the driver IC being shot. the individual transistors seem ok but I haven't had time to get in and have a good look.