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  #46  
Old 11-09-2018, 04:34 PM
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Dubis7 Dubis7 is offline
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Well, I just cleaned all the tube pins and sockets. Doesn't appear to have had an impact.

If it means anything, it seems like, on power up, it doesn't flicker. It only starts after a few moments.
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  #47  
Old 11-09-2018, 07:03 PM
old_coot88 old_coot88 is offline
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It could be a microphonic tube. Try tapping each tube individually in the tuner, IF, and video chain while watching the screen in a mirror.
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  #48  
Old 11-10-2018, 03:05 PM
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As old coot said LIGHT tapping of tubes is a good start. Also you can
lightly push the tubes to look for dirty / bad sockets. Its all about
localizing the problem .......

On sets built with PCB's & a steel frame the boards are soldered or
screwed to the chassis. The steel is a huge ground & all those mounting
point need to be good. Also look at shields around the IF's. They often
complete grounds & get cold joints.

One last tip. Tube pins can be cleaned with dikes. Lightly grab the pins
& shave them. For the sockets as a last resort you can tighten most of
them with a jewelers screwdriver form the top.

What the hell, one more......
RCA tuners. To clean an RCA tuner especially one using the Nuvista
RF amp tube. Pull the tuner & remove both shields. ONLY put a small
amount of cleaner on the contacts. DO NOT just spray it ! Most cleaners
would turn the RF stage into an oscillator ! It was the first mistake I
made at the bench. Hell I didnt know ! The boss was cool about it. Had
to douche out the tuner with freon then trim the neutralizing cap.

73 Zeno
LFOD !
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  #49  
Old 11-11-2018, 04:02 PM
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Went ahead and did the tube tapping today. I got some odd results - tapping most of the tubes resulted in some level of flickering, but tapping the Video Output/AGC tube had an especially strong reaction. I also noticed that, after tapping them for awhile, the problem went away again. I've read that microphonic tubes can stop vibrating for awhile if you touch them just right, so maybe that's what happened? Anyway, the problem came back after I put the back back on, so I've gone ahead and ordered a replacement output/AGC tube, and I'll see how that impacts things.
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  #50  
Old 11-21-2018, 04:20 PM
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Alright, I'm back with good news. After my tube was dropped at the wrong address, then retrieved and delivered correctly the next day, I was able to test the swap. Sure enough, the new Output/AGC tube has cured my picture flickering. I'm going to call this project wrapped for now. Once my paycheck comes in, I'll be picking up one of those little cheap RF adapters so I can put up my test pattern DVD and align the picture, and I've got a few cosmetic things to replace. I'm looking for a new back, the gold trim has a chip in it I'm planning to fill in and repaint, there's a gouge in the black trim around the picture tube, and the silver paint accent around the trim is wearing away. Eventually, I'll get some information and hopefully a new back and get it all cleaned up.

Thanks again to everyone that helped me through this one! I'll always get a chuckle out of the fact that the entire problem I set out to solve in the first place was a simple tube swap.
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  #51  
Old 11-21-2018, 06:29 PM
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First roundy I did was like that...Bugged the ARF folks, wracked my brain, gave up for a while then pulled the shorted (since previous test) damper out to put in another set that had an intermittent damper short that was causing flickering and that set went dead...Then I quickly went from stalled to all wheels turning full speed/completed resto.
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  #52  
Old 07-10-2019, 12:37 PM
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Okay, well, I'm back with a new problem.

After using this without problem for a few months, I suddenly starting having some bizarre intermittent issues with the picture and audio. It would run fine for awhile, then suddenly the entire set would have this dip where the picture would become blurry and dim and the audio would hum, and then it would pop back to normal. It kept doing this on and off every 20 seconds or so. I switched it off, fiddled with the antenna and all that, and eventually got it working fine by plugging it directly into the wall instead of using it on a power strip.

So, okay, maybe that's the problem?

Except then it started up again. Same issue, and it's gotten worse. When I unplug the converter box and antenna, I'm getting a sort of grainy, lit screen, but there's no "snow" if that makes sense. At this point, it's doing it all the time on power up.

Here's a video of what it looks and sounds like as of today: https://www.youtube.com/watch?v=1joh...ature=youtu.be

I have a couple theories. First, I ordered a few new tubes for the tuner. I'm thinking I may have a dying RF amp tube, but that's just a wild guess. I suppose it could also be a weak mixer/oscillator. Whatever the problem is, it has to be before the audio and video are separated.

I'm also wondering if there isn't a wiring problem in the wall, since it got better before when I switched to a direct connection. I'm going to try moving to a different location and seeing if that improves things. If it does, I may be looking at a house problem and not a television problem.

If anyone has any theories on what this looks like, though, please let me know. I'm a bit stumped by the fact that, at least before today, it would be fine for awhile before suddenly doing this. Seems like a heating problem, which is why I'm saying tube, but I'm no expert.
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  #53  
Old 07-10-2019, 12:45 PM
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Okay, same problem, but I was able to capture the intermittent nature this time.

One thing I forgot to mention is that tapping near the tuner seems to impact it. I didn't capture that part effectively, but it went from normal static visual and audio to everything cutting in and out maybe ever 20 seconds. Then I tapped the cabinet near the tuner and it started cutting in and out much faster. Loose connection somewhere, maybe?

Anyway, here's the video: https://www.youtube.com/watch?v=yXLR...ature=youtu.be

I may see about pulling the back off and reseating the tubes at least. Not sure if that'll do much or not, but I suppose it can't hurt.
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  #54  
Old 07-10-2019, 06:36 PM
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Unlikely that your power connection has anything to do with it, since the raster is not shrinking when the video and audio disturbance occurs.

Reseating the tubes is a good first try, but if/when that doesn't work, the next thing might be to tap/prod various internal places, bend wiring, etc. with an insulated stick to see if you can find the intermittent item. Edit: I think I would start with the cables connecting between the tuner and the main chassis.
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  #55  
Old 07-11-2019, 03:37 PM
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Okay, so this is weird.

The new RF amp tube came in. I swapped them out, and it ran fine for a bit. I actually noticed that the audio static was there, but the snow was absent, but I figured it wasn't getting a strong signal since the antenna was disconnected, so I put the back on and sure enough the snow came back.

It ran fine for awhile, then started cutting in and out again, so I took the back off.

Now I have snow, everything looks normal, and as of yet (probably about 15 minutes) there's no signal loss. Tapping tubes and playing with wires isn't changing anything either.

Any ideas?
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  #56  
Old 07-11-2019, 04:39 PM
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OK, you have snow and no intermittent with the back off.

I'm stumped, but would try putting the back on again.

Having snow is normal, but if it goes away to a blank picture again, it means that the signal path is broken somewhere in the tuner or IF or the connection between them, or the AGC voltage has gone wacky. How putting the back on could cause this, i have no idea, but that's the only indication you have so far. Could it be a heat problem opening up a connection? Don't just tap the tubes, grab a cloth or something to keep from burning your fingers, and wiggle the tubes.

Edit: Also, what happens if you wiggle the channel selector?

Normal operation with no signal should always give you snow.
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  #57  
Old 07-11-2019, 08:50 PM
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Dubis7 Dubis7 is offline
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I was able to find a consistent pattern, if that helps. If I turn it on, then switch it back off and back on after a moment, it loses audio and video and makes a sort of whining noise before it comes back on fully.

https://www.youtube.com/watch?v=ilmJ...ature=youtu.be

I'm going to try running it with the back off again, if only because the intermittent nature may mean the normal behavior when the back was off was coincidental.

This is definitely a signal problem, though. I'm just not sure how to proceed.
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  #58  
Old 07-11-2019, 08:55 PM
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Slight update: Audio is getting through but video isn't. So maybe this is a video only problem? The audio seemed like it was having trouble before, though, and I'm not sure but I think the volume is lower? Unfortunately a lot of this is very subjective.
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  #59  
Old 07-12-2019, 07:29 PM
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Okay, well, the new Mixer/Oscillator tube came in today. I swapped that and have been running it with the back on for hours now. Haven't had a single issue, everything seems rock solid, and it considering the previous behavior it would have started acting up by now. So I'm going to say I had some sort of intermittent issue with that tube. I may swap the old one back in later and see if the failure comes back, just to prove it, but so far so good.
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