[TV MAN]

Thanks Rich! This is kinda typical in TV work and is one reason I don't shotgun things. If something like this goes wrong, it could end up scrapping an otherwise well done revamp. One thing at a time on TV work.

THIS is why I do things as I do them! Do a section, test, do something else, test. One thing at a time. Oh, and those solder blobs and disappearing clipped capacitor leads? Where do those things go?

Ok, so I'm going to have to do this a section at a time. I have HV, so I should get SOMETHING on the screen, even a dot. The tubes are all lit so I know the big tube is lit also. There's voltages on the audio section. Voltages on the CRT cathode - BUT - NO change when I turn the brightness control! It stays at 120v which is full cutoff. Ah Ha! But - why??? I check the resistor to ground and resistance of the control - oooohhhoooh! Something weird. Very weird! When I check across the 47K resistor from the control to ground, it checks fine. yet, when I check from that control to ground, open! So I check the cathode of the audio driver tube - connected to ground - OPEN! What??? It seems I've somehow lost my ground in that entire section of the set! Which affects the audio and picture brightness.

So, after some troubleshooting I did find the culprit. Do you see it? Yup, A broken ground wire! Yup, one of those that I had to move several times in replacing caps and resistors. but, why it worked fine until I flipped the set to service the top? Nothing touched it. But, if that clip on the 1B3 was that brittle, the wiring in this set may not be much better. Who knows. That one was a hard one to see and took visual tracing and the ohm meter to find. Oh, BTW, if I hadn't mentioned it before, this is a kind of floating chassis where the B- isn't chassis ground, but wired point to point.

   
   

I did some checking and found a more "proper" RCA 12AU7 tube to put in and save this precious one pictured for something more special. Some audiophool would probably have a heart attack knowing that this beauty found it's way into an old TV like this. I think I'll hang onto it and sell it later for my retirement I am kinda starting to doubt that I killed that original tube - I recalled that one of the 12AU7 tubes didn't want to light up in the tester, and I had to unplug it a couple times before it lit up and I could test. Dirty contacts? Maybe. Maybe not. Anyway, it was pretty weak, but with the prices of those tubes I decided that if it worked - it would be used. Well - it did-n't!

   

Next this happened. The photo isn't great, it likes to blank, but it has a truly wonderful picture now! But ... the sound?? Well - what sound?   So, here I go again. It IS different that I can buzz the volume control and get that "buzz", so I know it's working from that point forward, and the sound takeoff is right off the video amp tube, and since I have a good picture, I know things are working to that point. So, its between there and the volume control. Time to go hunting - again.

   

EDIT: Problem found and now the set is working as before. Some signal tracing showed a dead volume control, which ended up being a shorted audio coax cable running through the set. The insulation on the center conductor had broken off allowing it to short to the shield. Now, I'll get that repaired, adjusted in and hopefully do a burn in and wrap this one up. Need to adjust the discriminator coil and hopefully clean up the sound and clean some controls. Again - from moving stuff around, which I have to do in order to replace suspect parts.

[morzh]

I know from experience: there's nothing like the feeling of having just fixed the problem thatyou yourself created.
I am sure it calls for a beer and some warm fuzzy feeling.