Dell Ultrascan P991 no image.

[josejl]

Hello. A few months ago I bought a Dell P991. I was very happy with purchase, geometry was near perfect and the colours were great.
However, two days ago, I was using it, and the image blinked once, but it recovered. 10 minutes, it blinked again, and the image was completely gone.

This is what happens when I try to turn it on.

https://www.youtube.com/watch?v=ENFNS1-DYYc

All electronic shops in my area refuse to do repairs on CRT, so I was wondering what could be the issue.

Thanks

[momaka]

Re: Dell Ultrascan P991 no image.

Sounds like either the PSU is having a hard time coming up due to something shorted or tube gone to air. Judging by the sound, I don't think it's the flyback, as it sounds like the HV is trying to come up.

So open the monitor and take a video of the back area where the neck board goes onto the CRT tube. If there is a cover on the neck board, remove it so it is visible. Then try powering the CRT monitor On. Do you see any of the spark gaps (little glass tubes) on the neck board or the D board sparking inside? If you post a picture with the back off, I should be able to identify them for you.

[josejl]

Re: Dell Ultrascan P991 no image.

I think the one at the start of the video should be it? This one sure has a lot of shielding compared to the other CRTs I have opened (just for minor adjustments to G2/Focus). I saw the anode cable being attached on the right side one, so I didn't want to remove it for safety. My knowledge of electronics is very limited, so I'm quite paranoid about touching anything I am not 100% sure.

https://www.youtube.com/watch?v=Ha6MhpXGdzY

[momaka]

Re: Dell Ultrascan P991 no image.

Can't 100% tell, but it looks like either the flyback is arcing to something or the HV anode wire is arcing to something.
If it's the former, the only way to fix this would be a new flyback.
If it's the latter, you can try to insulate where the wire arcs... though that may not be easy.

Can you still provide some pictures of the CRT monitor back area? I just want to see (if possible) where the spark gaps are relative to the flyback so I can have a better idea of where the arcing might be coming from.

And yeah, no worries about getting shocked from the monitor in this condition. The HV arcing like that means the tube is almost or fully discharged. Even the primary cap in the PSU will likely be discharged. So as long as the monitor is unplugged, you should be pretty safe to touch in there or disassemble it. But again, before we get to that, if you can provide some pictures and also indicate on them where the arcing is exactly, that would be great. The video is a bit blurry so I cannot pinpoint it exactly.

[josejl]

I was able to remove the shielding, but video still remains quite blurry. However, I was able to pinpoint where it's happening. Spark gap SG901

You can see the schematics in the service manual for this monitor, the Dell P991 seems to be a rebrand of this model

https://www.manualslib.com/manual/24...-Cpd-G400.html