NEC Accusync 120 21" monitor with intermittent size problem?

[Aslaner]

I have this unit which changes size from time to time. Almost like a slight
zoom in and then zoom back out.
The picture is great, I have redone all cold joints, looked for bad caps,
not sure what is causing this.

 

[Jerry G.]

This can be mostly from the power supply not being stable, or the HV
multiplier module is going defective.

You can verify the power suppy, by monitoring its voltages with a DVM
to start with. If the supply is stable, a new HV multiplier module
should be tried. If I remember correctly, this module is part of the
flyback assy.

It may not be worth to service this monitor.

Jerry G.
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[Aslaner]

I have just found where the problem reside.
behind the flyback and close the board at the back, there is a little added
cct board
when I move it, the size changes.
I suspect the problem reside there.