Tatung CM-1495 monitor repair (Badged Gateway 2000)

[Skip94]

Hi all
I have here a Tatung CM 1495, badged as a Gateway 2000. It takes TTL or analogue inputs so would be nice to get working.
This is, internally, almost identical to a TVM "Multi-Function/2 Colour monitor", to the point that the PSU, board with the flyback on and the neck board are identical. The other two boards differ slightly. I know this as I have loan of a fully working TVM monitor.
So far on the Tatung I have repaired cracks on two of the PCBs, and run bodge wires where traces were broken. It appears to have suffered this damage in shipping.
This got the monitor to the state where it powers on and displays an image on the screen.
However this image is flickery and has a rainbow effect to it, so obviously something is still wrong.
A very similar issue is talked about here
And here
These are both regarding the TVM monitor, but as I say, they are near enough identical.
But unfortunately no solutions were posted.
I have uploaded a video of its behaviour here
As it hasn't entirely failed and hasn't lost just one colour, I'm a little unsure where to look next.
I'm wondering if it could be a capacitor problem, but I dislike the approach of recapping things just because they are old, I'm hoping to narrow down where to look a little first.
Does anyone have any thoughts?
Cheers
Andrew

 

[Skip94]

I've been doing a little more tinkering.
I've narrowed the problem down to this board. I fitted the one from the TVM monitor I have into it and the flickering goes away.
The colours are still slightly off in places, but can be got almost correct with a magnet in the top corner. The more I use it the better it seems to get, so I suspect it just needs a thorough degaussing.
So now to diagnose whats causing the flickering with the original "main" board.
This board is the one that is cracked, but I have been over the damaged area with a multimeter and cannot find any traces that are broken, except for the 3 I repaired.
I have gone ahead and ordered new caps for this board too, they weren't expensive and it'll be something else I can rule out. I'll probably reflow the whole board while I'm there too. I can't see any bad solder joints, but my eyes aren't always the best.
Luckily all the ICs on the board I can still get easily, if it turns out one of those is at fault.
Andrew

 

[Skip94]

Would probably help if I attached the pictures
In the 1st one, the top board is the dead one, the bottom one the good one.
Andrew

 

[Skip94]

Fixed!
Recapped the above board and I now have a stable image. Colours are still off in places, but I did knock one of the little rings onnthe neck of the CRT slightly, so will play with those. As this recap did so much, I'll go through and recap all the other boards.
Andrew

 

[gatewayrepairs1985]

Fixed!
Recapped the above board and I now have a stable image. Colours are still off in places, but I did knock one of the little rings onnthe neck of the CRT slightly, so will play with those. As this recap did so much, I'll go through and recap all the other boards.
Andrew

Great job recapping the board! Did you ever end up fixing the colors on this monitor as well?

 

[Skip94]

Great job recapping the board! Did you ever end up fixing the colors on this monitor as well?

Thanks, it was a long process, but I think well worth it.
No joy with the colours and the focus seems a bit off across the tube. I can get it right in one place or another, but not across the screen. I'm tempted to try a tube swap from the good monitor, as I suspect the current tube has been damaged. This monitor certainly suffered a lot in shipping.
Andrew

 

[gatewayrepairs1985]

Thanks, it was a long process, but I think well worth it.
No joy with the colours and the focus seems a bit off across the tube. I can get it right in one place or another, but not across the screen. I'm tempted to try a tube swap from the good monitor, as I suspect the current tube has been damaged. This monitor certainly suffered a lot in shipping.
Andrew

Ah, I see. Still super cool that you have the skills to restore these old monitors - glad you were able to get it at least partially working!