DuMont RA-103 Doghouse lives . . . kinda.

[bigaudioal]

Thanks for the suggestions. Glad I am learning enough to recognize what sections to concentrate on and my inclinations to concentrate on the vertical circuitry, VOT and yoke were good.

Bob, I do not have a scope yet, so flying blind when it comes to wave forms.

Tom, I have replaced all the candohms and resistors over 1 watt in the set. All caps are done (minus micas and some ceramic pf caps). All resistors and ceramic pf caps in vertical are replaced now too. I did try various tube swapping for the vertical section with no change.

I will proceed to test voltages on the vertical tubes, check wiring and controls, then ohm out the VOT and see where that gets me.

One thing that you did mention Tom, is that vertical switch on the back. It does function and adjusts the top part of the picture from WAY OFF the top edge of the CRT in one position, then moves the top part of the picture down in the other position. Which is the position I took the photos in. The overall poor vertical appearance does not change in either switch position however. I will try cleaning that switch too.

This is where the fun begins!!! Trying to track down what is off with my limited experience and knowledge. Thanks again for the nudges in the right directions.

[John Marinello]

I think it's a sawtooth issue as well, but make sure height + linearity adjustments are OK first, as those way off can produce a similar effect.

[bigaudioal]

Ok, so here is the loaded question.

If everything else checks out and tube swapping, caps/resistor checking, etc. fail to change the condition and we are looking at a possible sawtooth waveform issue - where do I go from there? That waveform comes from vertical osc tube, correct? So either the voltages are fine on that tube and the issue is with the tube itself, or the voltages are off and I have to track down where the problem lies feeding that tube, right? So test voltages back from tube to tube in vertical before osc tube until I get to a point where they are correct. Then my issue lies between osc and where they test fine.

This is all assuming that controls/caps/resistors, etc are all done and good. Just wanting to make sure I have the concept down really for diagnosing.