1950 Philharmonic 8200 Audio Issues

[JohnCT]

Originally Posted by vortalexfan

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.

Both vert and horiz? Odd. I'm assuming it's been completely recapped and resistors are close in value.

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

[vortalexfan]

Originally Posted by JohnCT

Both vert and horiz? Odd. I'm assuming it's been completely recapped and resistors are close in value.

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

Yes, if the TV has been sitting for more than 24 hours and I try to turn it on, I don't hear the loud buzzing noise you hear when the TV's Vertical and Horizontal Oscillators and the High Voltage kick in, it doesn't kick in until I turn off and turn on the TV a couple of times.

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?

[JohnCT]

Originally Posted by vortalexfan

... 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.

Just to be clear, when you lost the picture and sound, you were left with a blank raster with no snow, correct?

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

[vortalexfan]

Originally Posted by JohnCT

Just to be clear, when you lost the picture and sound, you were left with a blank raster with no snow, correct?

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

The picture went to a black blank screen, and no audio.

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.

[JohnCT]

Originally Posted by vortalexfan

The picture went to a black blank screen, and no audio.

Is there HV? A problem in the tuner or IF will still leave a raster if the brightness is midrange or higher.

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).

Originally Posted by vortalexfan

Maybe I should try checking those tubes and replacing them with new ones?

I'm not one of those guys that says never use a tube tester; I have several and find them useful to a degree. But what you need instead of a tube tester at this point is a good meter and a good scope (and an iso trans if it's a hot chassis).

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

[vortalexfan]

Originally Posted by JohnCT

Is there HV? A problem in the tuner or IF will still leave a raster if the brightness is midrange or higher.

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).




I'm not one of those guys that says never use a tube tester; I have several and find them useful to a degree. But what you need instead of a tube tester at this point is a good meter and a good scope (and an iso trans if it's a hot chassis).

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

Well I figured out what the problem was and I got it working like it should now.
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.