Mighty Monarch of The Air

[old_coot88]

Originally Posted by vts1134

New cap same problem .

Well doggone. Did you connect the + end of the cap directly to pin 8, and the other end to ground? (Some foreign-sourced electrolytics have an arrow pointing to the [-] end of the unit, which can trick you as to which polarity it's signifying.)

Might R3 be the problem?

Not likely if it measures (approx.) 5K and shows no dead spots or drop-outs throughout its rotation.

I'm going to try again to get the real replacement for T2 to eliminate that from the equation also.

[vts1134]

R3 reads 5k on the high side and just a couple of ohms on the low side. There are no dropouts or dead spots in the rotation. C1B used to connect to pin 8 with a wire. I removed the wire since I was no longer using a multi stage can and now have the electrolytic directly on pin 8 and the negative right to ground. Here's hoping a new T2 will be the answer.

[VintagePC]

If you have the proper resistors to match the new T2's resistance to the original, you can try that too. I doubt it would work, but if it does, it might save a few bucks on trying to locate a matching part elsewhere.

[vts1134]

New transformer same problem . I will return to the schematic for component by component tracing soon.

[VintagePC]

Sounds like it's time to break out the scope

Tracing waveforms can get you a good idea of where the problem lies. Do you have a reference of what they should look like? (Usually in a Sam's)

Also, if you have substitute tubes, it may be worth trying those too. Some sets drive them to their design limits, and the result is a set that works perfectly with one tube, but not another that is slightly out of spec. Both tubes will still test good, of course, so the easiest way to find this problem is what's called the "tube roll" (swapping tubes in the problem areas with another one).

[Phil Nelson]

Originally Posted by VintagePC

the result is a set that works perfectly with one tube, but not another that is slightly out of spec. Both tubes will still test good

I have found that to be the case with oscillator tubes, especially. Sometimes I have had to swap in several horizontal oscillator tubes before finding one that the TV "liked."

Speaking of oscillators, are the voltages on V13 still as far off as before?

Looking at waveforms with a scope seems sensible. This schematic doesn't give models, but you could start by looking at the grids of V13 (oscillator) and V14 (output) and posting photos of what the scope traces look like there.

Phil Nelson

[old_coot88]

Originally Posted by vts1134

New transformer same problem . I will return to the schematic for component by component tracing soon.

Well tarnation. Just out of curiosity, what voltage are you getting at the low/wiper end of the vert. size control? oc

[jeyurkon]

**I forgot about the recent progress and was commenting about an earlier state.**

[old_coot88]

Um.. just to reiterate what was suggested back in post# 62, the plate load resistor of the
V.oscillator is a very common failure point and should be double checked if you haven't already done so. Now that we got the schematic to look at, that would be R66, 470K (half a megohm +/- 10% or so).

And does the V.size control (R4) measure correctly at 2.5 meg or so?

How about the voltage at the bottom of R4? Since it's supplied from B boost, it should probably be somewhere around 400-450 V.

oc