Width adjustment stopped working on 1084S-P2.

[e5frog]

I was finally getting around to adjust the convergence on my 1084S-P2. After a bit of tinkering and adding two magnets I got the picture almost perfect - a lot better than when I started.

Adjusted picture height and positions, everything was nice so back on the shelf after attaching the rear part of the housing again. Big smile...

When turning it on again I had some picture flutter, small disturbances and picture was very wide. When trying to adjust the width, I got nothing, no change. The small disturbances stopped after a while and I assumed I had broken the pot or something.

Measured, desoldered, measured again, nothing wrong with that, soldered it back on and found the service manual for the 1084S-P1. Schematic is very hard to read... Seems there's a few resistors and then it goes to the TDA IC.
Checked the voltage on the first pin, it was -26V, according to the schematic for the "1084pal2" that voltage is -21V - for that one at least. When adjusting the pot I can change the voltage from -26V to almost 0V (-0.2 or so).

So I guess that IC could be broken.

Does anyone have any good tips or a better schematic, preferably for the 1084S-P2.

Don't know what could have happened, it's pretty annoying now that I got the picture right again.

[Toni Wilen]

Does image geometry still look correct? (Straight lines don't become curved near the edges etc)

EDIT: Asking because I had old monitor that had stuck full-width screen with bad edge geometry, problem was caused by shorted diode. Unfortunately I don't remember anymore what its function was.

[e5frog]

Yes, geometry is otherwise near perfect.
Guess I should discharge it, pull the PCB out and trace the signal... *sigh*

Well, yes, it could be something as simple as that.

[e5frog]

Discharged the tube, disconnected and desoldered enough to get the PCB out of the monitor, started looking for errors after also contacting Ray Carlsen for support and tips...

After checking most stuff such as diodes, resistors, with some help from the 1084S-P1 hardly readable schematic and resoldering some recommended components I also desoldered the cage on the bottom of the PCB - there I find a small strand of dremel metal brush, stuck to one of the pins of the large upright coil in the upper cage and touching the cage of course - so it was shorted out and no adjustment could be made - apparently.

As I had taken the time to tear it all down I proceeded to check solder joints and made sure all diodes measured OK, then reassembled and everything was working again. Screen is nice and sharp again all controls are working!

My own fault for using the dremel with a bare PCB on the table - I'll try not to do that again - or at least with a better quality brush that doesn't shed...