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#16
04-12-2020, 10:23 PM
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#17
04-16-2020, 10:59 PM
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Well I got some new 6T8 tubes and installed one of them into this TV and I got the audio to work just long enough for me to get the Video IF adjustments adjusted to where they should be so then I shut the TV off thinking the Audio issue was fixed, but then when I went to turn the TV back on again later on in the evening to make sure it was still working correctly and the audio was gone again and this time I didn't do anything to it to cause the audio to go away, it disappeared on its own this time, and I tried everything I could think of to try and get the audio to come back including swapping in another 6T8 tube and it wouldn't come back.
And I'm not sure what's going on with the audio on this TV as it was working fine until just recently.
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#18
04-17-2020, 11:45 AM
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Bad sockets?
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#19
04-17-2020, 11:55 AM
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#20
04-18-2020, 12:41 AM
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Well I figured out what part of my problem was with this TV's audio problem,
there was a resistor that came loose from where it was soldered to, which I had resoldered the loose resistor back to where it was supposed to go, but it didn't fix the audio issue like I thought it should of. Below is the schematic with the areas in the audio section giving me troubles and the resistor that was loose that I repaired marked out as well.
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#21
04-20-2020, 01:33 PM
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OK, SO I think I figured out what's going on with this TV, I think it has something to do with the tuner, as I was able to get the audio to come back on again today but then when I went to readjust the IF again (as it was out of whack again) my screwdriver slipped and hit the chassis of the tuner itself and then both the picture and audio disappeared.
So it seems the tuner may need some work done to it. Also another thing I've noticed is that my High Voltage and Vertical and Horizontal Oscillators don't start on the first try when I first turn on this TV, it usually takes 2 or 3 tries to get it to come on properly. Any ideas as to what that's all about?
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#22
04-20-2020, 02:04 PM
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Tubes would be my first suspicion followed by carbonized tube sockets then osc coils. Have you scoped them to confirm the oscillators are not running? This could also be thermal. You can try preheating the chassis with a heat gun and see if it starts reliably. If so, you may be able to pin it down with heat and freeze spray. John
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#23
04-20-2020, 11:39 PM
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The reason why I know that the oscillators aren't running for the Vertical or Horizontal is because It doesn't make the distinct high pitched whistling noise that the oscillators make when they are running, and when the High Voltage is running I can usually smell a little bit of an ozone smell when the high voltage first starts running, wheras when the High Voltage isn't running there isn't any ozone smell, also no picture shows up on the screen even after all the tubes have warmed up including the picture tube. Yes the TV has been completely recapped and all out of tolerance resistors replaced with modern carbon film and metal film resistors. I was able to get the audio to come back again but then when I went to readjust the video and audio IF transformers again because they drifted out of adjustment, so when I went to readjust the 1st Video IF adjustment which is on the Tuner Chassis, my screwdriver I was using slipped off the adjustment screw and hit the tuner chassis which then caused me to lose my picture and audio both this time around and when I try tapping the tuner chassis the picture flashes back on temporarily but then goes away again. Which makes me think that my audio problems were and are related to the tuner. What are your thoughts?
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#24
04-21-2020, 06:10 AM
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Sometimes we get lost trying to find a problem because of *too much* knowledge. I would forget about the slipped screwdriver and troubleshoot this like it came in to my shop with no sound and no picture, so that means verifying all voltages in the tuner and IF section, and trying some tubes. Tubes become shock sensitive at times. Maybe the slipped screwdriver caused an overvoltage in one of your tube elements. Since you seem to have a whole bag of what seem to be unrelated issues, I would again check the power supply voltages and scope them to make sure they're clean. John
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#25
04-21-2020, 08:07 AM
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There are a couple of the Video IF tubes in the TV that are original to the set (they were Meck branded because they made the TV for Philharmonic). Maybe I should try checking those tubes and replacing them with new ones? Also I don't really have any 6AU6 tubes except what came with this tv, I do have some 6BA6 tubes which are listed as appropriate substitutes for the 6AU6.
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#26
04-21-2020, 04:09 PM
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Suspect all tubes even ones you have newly installed. One of the longest times I ever chassed my own tail troubleshooting was when I assumed that the damper on a set that had worked prior to a recap had to still be good afterwards....the tube had randomly died and it took me borrowing it to use it in another set for me to get past my stupid preconceived notion that it couldn't have just randomly died.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#27
04-21-2020, 04:53 PM
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Maybe tapping around the tuner is causing a sympathetic vibration somewhere in the sweep section and restoring deflection and/or HV. Again, troubleshoot this forgetting everything you know about the TV (other than it worked after being recapped). Quote:
I would start with the basics. Check the HV. Arc the cap of the HV rect to the cage. Scope the horiz drive to the horiz output. Check DC voltages at the CRT. If it has raster, scope the video from the detector back through the IFs. A signal generator or a dedicated device like a B&K 1070/1077B or Sencore VA48/62 will allow you substitute drive and low level signals to see what's good and what's not. John
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#28
04-21-2020, 06:58 PM
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My power supply caps were shorting against the chassis and some of the resistors for the Power supply circuit. Because of how cramped it was by the power supply area of the chassis, when I originally replaced the old power supply filter caps I had to just use a free floating terminal strip for the power supply filter caps because there wasn't enough room for me to get a soldering gun into the chassis to solder the terminal strip to the chassis without accidentally burning through wiring insulation. So apparently what the problem was that I didn't get the terminal strip situated so that it was sitting completely horizontal against the chassis so that the filter caps weren't touching the chassis or anything else near it, so when I hit the chassis with the screwdriver when it slipped the vibration of the screwdriver hitting the chassis was causing the terminal strip to move just enough to short the filter caps to the chassis and other components nearby which is why i would loose my audio and then eventually my video as well. So I fixed the filter caps and I now have video and audio again.
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#29
04-26-2020, 09:14 AM
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A note: This Philharmonic began as the company founded by Avery Fisher in 1937. Avery Fisher lost control of the company due to WW II production and the need for more capital for the business. Avery Fisher left Philharmonic Radio in 1945, and began Fisher Radio. John Meck acquired the remains of Philharmonic in the 1950 time frame.
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#30
04-26-2020, 10:37 AM
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Linear Mode
