[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.

[TV MAN]

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.

[TV MAN]

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.

[GarySP]

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

[radiorich]

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

[TV MAN]

So far, this little TV is holding it's own. I tried using an older ('90s) VCR and it worked great. I can plug in a DVD and use it for a modulator and works very good. Very little buzz in the sound, nice clean pic. The Blonder Tongue modulator does fine, So, it seems a stand alone modulator or set-top box either is slightly off frequency, over powers the AGC, or something. Still fighting a light hum bar, so I'm going to double check my power supply and filteration and lead dress. I also noted some retrace lines on a dark or blank scene, but this could be the nature of this set. Most notable when the contrast is turned down. Richard, get a TV on your bench and go after it! It wont fix itself!

[MuzzcoVW]

Nice work Tim! And, overpowering the AGC was one of my thoughts. You've got to love those "why is it doing that!?" moments at the bench! Craig

[MrFixr55]

Hi Tim,

Nice job! Was that a broken cold joint on one of those resistors by the transformer in one of those pics? Weah, the hum bar is puzzling. You state that it does not occur on the upper channels. Does it occur on the lower channels without a signal? Most NTSC RF Modulators allow a choice only between ch3 and 4. Does your RF Modulator allow selection of other frequencies? Does it hum on Ch 5 and 6, but not 7 and higher? Is there noise in the sound also?

Do you have an ATSC to NTSC convertor or AV jacks on the back of your cable box? (Mine has both HDMI and NTSC outputs.)

My experience with PS induced hum (from bad filters) in TVs was a slowly moving bar, or in some cases, slowly moving distortion in both horizontal and vertical planes.

PS- Mullard HiFi tubes are preferred to almost anything other than Telefunken, but I think that the holy grail tubes are Mullard or Telefunken 12AX7s as they are used extensively in classic HiFi and Guitar amps. 12AU7s and especially 12AT7s are not as popular in Audio circuits.

[TV MAN]

I believe I broke the wire when I was in there changing caps and such. The hum is a little puzzling. I can see it even if I inject a video signal in the video amp, but as soon as I flip the clunker between channels, it goes away, and the higher channel, the less notable the hum is. It's not a deal breaker by any means, just a little annoying. I don't know if Mr Anderson had any problem with this in his Emerson or not. Sync is solid, I only note it in the raster with a signal. And the stronger signal, the more predominate. Really not sure if it's coming in from an outside source somehow or from inside. Mr. Anderson, if you happen to see this, what are your thoughts and experiences with these issues on yours?

Take a look at the picture. It slowly moves up. I might take the TV someplace else and check in case I have something in the house causing this. I have always had hum issues in this house for some reason. Cant hardly listen to AM, so this could very well be external.