After more experimenting, including reproducing the issues on another PC, I've pinpointed the cause of the problem to be the built in VGA cable attached to the monitor. There appear to be some poor connections internally in the cable close to the VGA plug. The cable is very sensitive to any movement there, ending the signal, giving the blue display, or causing other display issues if the cable is moved around just a little bit in that location, even while the plug remains firmly in the PC's VGA port. Sadly it seems so sensitive that, for instance, just leaving the cable attached to my PC and allowing it to slightly move due to gravity is enough to cause the connection to go haywire.

dukeofurl wrote on 2024-12-07, 22:27:

After more experimenting, including reproducing the issues on another PC, I've pinpointed the cause of the problem to be the built in VGA cable attached to the monitor. There appear to be some poor connections internally in the cable close to the VGA plug. The cable is very sensitive to any movement there, ending the signal, giving the blue display, or causing other display issues if the cable is moved around just a little bit in that location, even while the plug remains firmly in the PC's VGA port. Sadly it seems so sensitive that, for instance, just leaving the cable attached to my PC and allowing it to slightly move due to gravity is enough to cause the connection to go haywire.

I've had the exact same problem with a Sony 17Sf. I'm wondering if yours is actually a similar model but Gateway branded.

MMaximus wrote on 2024-12-07, 22:38:

dukeofurl wrote on 2024-12-07, 22:27:

After more experimenting, including reproducing the issues on another PC, I've pinpointed the cause of the problem to be the built in VGA cable attached to the monitor. There appear to be some poor connections internally in the cable close to the VGA plug. The cable is very sensitive to any movement there, ending the signal, giving the blue display, or causing other display issues if the cable is moved around just a little bit in that location, even while the plug remains firmly in the PC's VGA port. Sadly it seems so sensitive that, for instance, just leaving the cable attached to my PC and allowing it to slightly move due to gravity is enough to cause the connection to go haywire.

I've had the exact same problem with a Sony 17Sf. I'm wondering if yours is actually a similar model but Gateway branded.

That could be. Afaik the gateway vivitron monitors such as the one I have were simply rebadged Sony Trinitron monitors manufactured by Sony (there is also a 17 inch version of the gateway vivitron).

Did you wind up doing a fix?

Before I think about cutting the cable, I'd like to slip open the plastic case on the plug to look at the connections to the existing plug, though I can't see a way that it is supposed to come apart.

I've had similar issues with a screen. Integrated VGA cable and picture problems, and moving the VGA cable around would give variations in the pictures (in my case, mostly losing red completely iirc)

Like in my case I doubt it's the cable itself, but probably old/cracked solder joints on the neckboard. The VGA cable is soldered to the neckboard, so either it's the cable's solder joints themselves, or moving the VGA cable around transfers movement/vibrations to the neckboard that triggers the problems because of other poor solder joints somewhere.

If you're confident working inside a CRT, I would try and reflow all solder joints on the neckboard.

In this case, moving the cable around on the plug end gives the issues while moving it around close to the monitor doesn't seem to do anything, so I'm hopeful it's not cracked connections on the neckboard.

Gotcha, hopefully you're right and manage to fix this nice monitor 😀

This monitor is totally fixed now. First off, the built in VGA cable did have very poor continuity, so a new cable from another monitor has been grafted in instead. That completely solved problems I'd have where the monitor would lose the video signal periodically, as well as bad v sync and bad color sometimes.

There was another issue where the display would frequently jitter. That was not solved with the cable replacement and I was thinking there could be one or more bad caps. However I found that the jitter would go away if I put pressure on the top of the monitors plastic case with my hand... And eventually I found it would also go away if I applied pressure from the bottom of the plastic case... Basically something to tilt the entire assembly forward a little bit... Yet it was not sufficient to simply tilt the monitor forward on it's pedestal, there had to be some pressure applied to slightly flex the plastic casing.

A local friend who is well versed in this stuff looked around extensively for bad solder joints but didn't find any. But in any case, wedging something under the case to apply a little bit of upward pressure right beneath the main pcb seems to do the trick. the jitter is entirely cured when doing this.

Here's a bunch of pics from my repair odyssey in case anyone's wondering what the inside of this monitor looks like.