1950s or '60s vintage Zenith TVs, Need some info

[old_coot88]

Originally Posted by vortalexfan

...I think maybe the negative lead of C3B isn't actually making contact with the chassis (its soldered in place but its not actually contacting the chassis its just "floating" there.

If the can IS actually floating electrically, it needs to be fixed as the first (not last) order of business. But there's still the separate issue of zero plate and G2 voltage (on pins 5 and 6 of the 5AQ5), as discussed previously. This wouldn't be caused by the floating can.

[vortalexfan]

Originally Posted by old_coot88

If the can IS actually floating electrically, it needs to be fixed as the first (not last) order of business. But there's still the separate issue of zero plate and G2 voltage (on pins 5 and 6 of the 5AQ5), as discussed previously. This wouldn't be caused the floating can.

1.) Yes, exactly, I do need to fix the floating negative on my replacement cap that I used to replace C3B that was in the can, and the floating negative lead would definitely cause my negative voltage readings in the audio circuitry.

2.) Yes I do still need to figure out the issue with the low voltage readings on pins 5 and 6 of the 6AQ5 tube socket and the none existing cathode voltage (which should be 17 volts but measures a measly 5 mV.)

3.) As for the floating ground issue, it is easy enough to do especially when you're trying to tie a new individual electrolytic cap negative lead onto a previously used chassis ground tie point that has tons of old solder already blobbed onto it.

[vortalexfan]

OK, I checked all of my negative lead connections on my electrolytics and they aren't floating, so that's not the problem.

But I think I definitely figured out this time for sure where my voltage is getting lost at on my Zenith Bugeye TV.

C49, a 470pF ceramic disc capacitor that goes from TS8-4 to chassis ground measures open (measuring the resistance across it, it quickly goes to O. L. from 25 MOhm and measuring it on my cap checker it measures 25pF, and when I measured the voltages across that cap my voltages were right there going to ground.

So am I onto something here?

[Kevin Kuehn]

Originally Posted by vortalexfan

OK, I checked all of my negative lead connections on my electrolytics and they aren't floating, so that's not the problem.

But I think I definitely figured out this time for sure where my voltage is getting lost at on my Zenith Bugeye TV.

C49, a 470pF ceramic disc capacitor that goes from TS8-4 to chassis ground measures open (measuring the resistance across it, it quickly goes to O. L. from 25 MOhm and measuring it on my cap checker it measures 25pF, and when I measured the voltages across that cap my voltages were right there going to ground.

So am I onto something here?

Are you measuring C49 out of circuit? And even if C49 were open it would have no influence on the weird B+ voltages you're reporting. I'd say it's nothing more than a RF filter to the audio signal leaving the detector plate.

Next definitely for sure possibility please.

[vortalexfan]

Originally Posted by Kevin Kuehn

Are you measuring C49 out of circuit? And even if C49 were open it would have no influence on the weird B+ voltages you're reporting. I'd say it's nothing more than a RF filter to the audio signal leaving the detector plate.

Next definitely for sure possibility please.

Well that capacitor though is where my voltages to the audio output circuit are getting lost though for sure because I measured the B+ voltage from the terminal that C49 ties to and goes to ground and I have B+ voltage there going to ground but then when I measure from that point to the other side of C50 the 10,000 pF ceramic disc cap there's no voltage there (it's -20V or so) and that is supposed to supply the voltages to pins 5 and 6 of the 6AQ5 tube, and yes I did replace C50 with a new capacitor finally and that didn't change the voltage readings any.

[Kevin Kuehn]

Originally Posted by vortalexfan

Well that capacitor though is where my voltages to the audio output circuit are getting lost though for sure because I measured the B+ voltage from the terminal that C49 ties to and goes to ground and I have B+ voltage there going to ground but then when I measure from that point to the other side of C50 the 10,000 pF ceramic disc cap there's no voltage there (it's -20V or so) and that is supposed to supply the voltages to pins 5 and 6 of the 6AQ5 tube, and yes I did replace C50 with a new capacitor finally and that didn't change the voltage readings any.

Let's get one thing straight here. B+ is not suppose to get to pins 5 and 6 of the 6AQ5 through C50. C50 is a audio signal coupling cap to the top of the volume control. C50's function is to pass the audio signal from the plate of the detector to the audio output grid. A capacitor is used because it's intended to block the B+ feeding the plate of the detector tube from getting into the grid circuit of the 6AQ5.

[vortalexfan]

Originally Posted by Kevin Kuehn

Let's get one thing straight here. B+ is not suppose to get to pins 5 and 6 of the 6AQ5 through C50. C50 is a audio signal coupling cap to the top of the volume control. C50's function is to pass the audio signal from the plate of the detector to the audio output grid. A capacitor is used because it's intended to block the B+ feeding the plate of the detector tube from getting into the grid circuit of the 6AQ5.

Well either way I'm not getting any audio out of the TV and I'm still not getting the 200+ volts I need to be getting on pins 5 and 6 of the 6AQ5 tube that the Sam's calls out and I'm not getting 17V on pin 2 of the 6AQ5 either, so I'm still stumped as to what's going on with the audio section of this TV, and I've still got no signal from the tuner to the TV on here either.