HP D8911 19" CRT losing red in integrated VGA cable (bad contact?)

Boohyaka

n00b
Joined
Aug 4, 2020
Messages
17
Hi guys, I need some help here... I have a beloved 19" HP CRT (D8911) and yesterday it starting having displays issues with what seemed like not being able to display the red color through the VGA input. At first I thought it was a warm up issue, but after a more thorough troubleshooting, it seems it was just a coincidence and the problem lies with the integrated VGA cable. My knowledge of CRT screens being pretty basic and having pretty much no real idea what I'm doing, and as I've heard both sides of the horror stories of working "inside" a CRT ("you will die" vs "it's exaggerated" basically), I prefer playing it safe and turning to the experts around here first.


Please follow the link above for a few pictures of the screen guts + a video showing the symptoms. In the video I'm basically holding the VGA cable to one side when the color is fine, and letting it go to its natural position when red disappears and white turns cyan (White being RGB, RGB-R = GB = Cyan) and yellow turns green (Yellow=RG, RG-R = G) so I believe my guess that only red component is missing makes sense. The 3rd picture shows where I'm holding the cable and moving it for the video.

Basically my questions are as follows:

- I also have a Sony G500 I've opened up recently to make a color calibration (see other thread on this very forum) and the tube and electron gun are basically inside their own metal chassis inside the plastic shell, making me feel very safe handling the whole thing. Here, the gun, tube and components are directly accessible once cover is removed. While the screen is disconnected from power, are there things I should avoid touching at any cost or any specific risk, or would it be only dangerous with the power cable connected? I see some huge capacitors and I'm concerned they may be charged even disconnected. In any case I currently feel unsafe turning the screen on without the cover to try and see what happens inside the case when I move the VGA cable around...
- I'm a bit puzzled by the fact moving the VGA cable outside the case has any effect at all, seeing how it seems to be build. The cable seems to be continuous from the external VGA connector, into the case through the hole at the holding neck, and straight inside the metal shell at the butt of the electron gun. So I don't understand how moving the cable around at the holding neck would make any difference as it looks like there's no connection or solder joint there...

My idea at this stage would be to try and dismantle the VGA cable at the holding neck to better see what it looks like, but just want to make sure it's safe to do and see if people have tips, suggestions or ideas about the issue altogether.

Thanks a lot for your help in saving this beautiful screen! :)

EDIT: discharged anode to ground with a flat screwdriver (no buzz or arc, slight pop only).
 
Last edited:

aeliusg

Gawd
Joined
Jan 14, 2016
Messages
771
Look, honestly you should go on badcaps or something like that where people have worked on hundreds of CRTs and could tell you off the bat what the issue is without a doubt. For general purpose CRT repair they have the knowledge. Logically it is probably a bad conductor in the cable. The high voltage stored in and around a CRT is not frequency modulated so if it discharges into your body it can cause fibrillation. People have died from it for sure. Discharge the tube as you did and let the set sit for a few days to a week to be absolutely sure.
 

Boohyaka

n00b
Joined
Aug 4, 2020
Messages
17
Thanks for the advice about badcaps, never heard of them! I'll keep it handy.

Latest update: I'm done I believe.. the VGA cable is indeed continuous, it was only held behind the cover to a ground. It currently looks like this:


...and it's happily showing perfect image with all colors.

Is there a good reason for that shield grounding on the VGA cable? Magnetic interference or something? Image looks great, so I guess I'll call it a day unless someone brings something new to the conversation.

Thanks!
 
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