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

[Kevin Kuehn]

Originally Posted by vortalexfan

I don't know how you could of missed this, but C50 has a lot more to do with the audio output circuit than you think it does, for example the 245V B+ supply is shared in common between the Audio Detector Tube and the Audio Output tube, and both supplies are filtered through C3B which are their common tie point in the 245V B+ supply through R54 and R56 (R54 feeds the 245V B+ supply line to the Detector Tube and R56 feeds the 245V B+ supply to the output tube and both of those resistors are tied to the positive side of C3B which is tied to chassis ground just like it was originally when it was in the old can cap, if you look at my schematic excerpt and my markings explaining where the negative voltages are being measured at and where the common points are in the two "unrelated circuits" you'll see that I'm not nuts in how I'm following this circuit layout and what I mean by the voltages after C50 are negative unless I reverse my leads.

I'm well aware B+ feeds multiple circuits. Are you saying you are measuring a negative voltage at point TS8-3 where you have circled, or everything to the right of that point including all the audio output voltages? C50 is an audio coupling cap and has absolutely no influence on B+, other than it could be leaky and letting B+ cross over to the volume control. If that cap is bothering you please remove it from the circuit.

[vortalexfan]

Originally Posted by Kevin Kuehn

I'm well aware B+ feeds multiple circuits. Are you saying you are measuring a negative voltage at point TS8-3 where you have circled, or everything to the right of that point including all the audio output voltages? C50 is an audio coupling cap and has absolutely no influence on B+, other than it could be leaky and letting B+ cross over to the volume control. If that cap is bothering you please remove it from the circuit.

I'm measuring a negative voltage at point TS8-3 and everything to the right of that in the TV's Audio Circuit, everything to the left of that measures normally (or as normally as a still malfunctioning TV can measure) which is the 210V that is supposed to be the 245V B+ Supply which is currently only measuring 210V right now.

[Kevin Kuehn]

Originally Posted by vortalexfan

I'm measuring a negative voltage at point TS8-3 and everything to the right of that in the TV's Audio Circuit, everything to the left of that measures normally (or as normally as a still malfunctioning TV can measure) which is the 210V that is supposed to be the 245V B+ Supply which is currently only measuring 210V right now.

How about you disconnect C50 and see if that negative voltage situation changes. I'm trying to get you to isolate one circuit from the other so we can make some progress and you're being very difficult to influence.

[vortalexfan]

Originally Posted by Kevin Kuehn

How about you disconnect C50 and see if that negative voltage situation changes. I'm trying to get you to isolate one circuit from the other so we can make some progress and you're being very difficult to influence.

I did disconnect it earlier and it did make somewhat of a difference but not a whole lot I wasn't getting negative voltages anymore but I was still getting only 22V on pins 5 and 6 of the 6AQ5 tube, so in that sense the removing C50 didn't affect the voltages but it did eliminate the weird negative voltage issue that was going on to the right of C50 in the audio circuit.

[Kevin Kuehn]

Originally Posted by vortalexfan

I did disconnect it earlier and it did make somewhat of a difference but not a whole lot I wasn't getting negative voltages anymore but I was still getting only 22V on pins 5 and 6 of the 6AQ5 tube, so in that sense the removing C50 didn't affect the voltages but it did eliminate the weird negative voltage issue that was going on to the right of C50 in the audio circuit.

Well for heavens sake please leave it out of the circuit if it eliminates the negative voltages. Unless you really enjoy banging your head on the wall. Then we can hone in on why the voltages are so low. Do you have a new capacitor you can replace C50 with?

[vortalexfan]

Originally Posted by Kevin Kuehn

Well for heavens sake please leave it out of the circuit if it eliminates the negative voltages. Unless you really enjoy banging your head on the wall. Then we can hone in on why the voltages are so low. Do you have a new capacitor you can replace C50 with?

No unfortunately I don't, but I have one on order from AES I ordered a 10,000pF 5kV ceramic disc cap from AES because the 5kV ceramic disc caps were the only ones that had the 10,000pF value without having to go into the polypropolene/Polystyrene/orange drop variety caps.

Anyways I'm very sorry I'm frustrating you, and believe me this is frustrating me just as much as it is you, because I was hoping that these Zenith TVs would just work after being recapped like my Meck TV did but unfortunately that's not the case here, these Zenith TVs are being stubborn and are not wanting to work correctly even after a recap job.

[Kevin Kuehn]

Originally Posted by vortalexfan

No unfortunately I don't, but I have one on order from AES I ordered a 10,000pF 5kV ceramic disc cap from AES because the 5kV ceramic disc caps were the only ones that had the 10,000pF value without having to go into the polypropolene/Polystyrene/orange drop variety caps.

I think 10,000 pf is the same as .01uf, no? At any rate that's what I'd put in there, or whatever you have that's close. It's an audio coupling cap so not that critical.