Quickie 6100 repair log

Just a quickie for you guys...
Had a 6100 that suddenly stopped giving me a picture. Spot killer
wasn't on, and a check with the o-scope showed that the game was
putting out good XY.

If I cranked the brightness, in a dark room, I could just barely make
out the picture, but it was way out of focus and doubled.

HV was good and it seemed that the deflection board was good... I
figured this was a problem with either the tube (it is a cocktail) or
the neckboard.

After doing some swapping around, I was surprised to learn that it
was, in fact the neckboard.

Cutting to the chase here, I figured there was a problem with the
filament line somewhere between the CRT socket and the low voltage
circuit, what is an LV2000 and tested good. I suspected D108, but
that tested OK also. Not much else to look at... I tested R107, and
it tested within 5% of the 7.5ohm it was supposed to be...

THEN, I tested the resistance between the "brown" filament wire post
and the anode of D108. Ahhhhh.... that measures in the megohms. I
removed R107, sanded and tinned the leads, and reinstalled it. I also
resoldered the post and D108. Now I'm getting about 8ohm between the
filament post and D108.

And the monitor works again!

Since this monitor worked for a long time, and nobody had ever touched
that resistor, I'm not sure how that connection suddenly went bad...
but it did. I'm not sure if just freshening up the solder on that
resistor would have helped matters, but it's never a bad idea to err
on the side of thoroughness.

I hope that somewhere down the road, this little repair log saves
somebody some time and hairs.

Later,
Rob
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