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1950 Emerson TV resurrection attempt
#31

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 Icon_lol 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? Icon_crazy  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.

If I could find the place called "Somewhere", I could find "Anything" Icon_confused

Tim

Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
#32

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

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#33

Icon_lol Ya got that right Mike! I watched it some last night for a couple hours and it seemed pretty stable. Not bad for a 75 year old TV! Probably still have a few tweaks to do and something could get off the mark, but aside from a couple fairly minor details, I think it's about ready to stuff back in it's box and call it good! It's not a daily driver, just something to fire up once in awhile and watch an old western or something.

If I could find the place called "Somewhere", I could find "Anything" Icon_confused

Tim

Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
#34

I've been "burning it in" last couple weeks and so far, it's behaving pretty good. It's weird having a lot of the controls on the back - backwards! Anyway, I do have a couple details I'm trying to get worked out. I have a light hum bar going up the screen and is most noticable on the lower channels, and doesn't care if the source is from a modulator or the B&K. It diminishes when I flip the clunker up to 5 or more. I  put the signal into the video and it's clean, but still shows up if I put the channel back to 3 or 4 with no signal. I think it's from the tuner somehow, but I don't know if it's picking up over the air or from within. I did swap tuner tubes with NOS without any change. So - not sure on that one yet. It may just be the nature of this TV.

Another thing that kinda has me scratching my head is that lousy sync buzz in the sound. Now, I can adjust the detector transformer and minimize it - but, it depends on the signal source. This is from a small modulator or RCA set top box but my Agile modulator acts different yet.  I can almost always adjust and minimize the buzz, but I shouldn't have to adjust this each time I change signal sources. I'm inclined to set it for the Agile since it is a commercial unit. Other than those minor annoyances, it is working very good. I'm about ready to put back in the cabinet and see if my resto was a success. It's a 75 year old set and a very simple one at that, so it wont have the filtering to clean out all the 'stuff' we have in the signal nowadays.


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If I could find the place called "Somewhere", I could find "Anything" Icon_confused

Tim

Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
#35

I admire your patience, Tim! Nice work. - Gary

"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
#36

Hello Tim,
The tv looks like it is working well thou.
Anyway I wish I had one of my antique tv's to restore here they are at my family's home only one Ihave here is a Sony Walkman tv and my 27 in Sony tv.

Sincerely Richard




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