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

[vortalexfan]

Originally Posted by Kevin Kuehn

You really don't want to run the set with the output transformer removed other than to take quick measurements because the 5AQ5 screen grid(pin 6) is still getting B+ and it's not healthy for the tube without the plate also getting B+. I really can't follow what you mean when you say everything after C50 is negative? Exactly where are you measuring negative voltage in respect to B- ?

I'd like to suggest we focus only on this little section instead of jumping all over the map. C50 is only a audio coupling cap that passes audio from the detector stage to the volume control, so we're really not worried about anything other than this little portion of the schematic. Once we figure out what's ailing the audio output then we can move onto the bigger picture.

OK so what I mean by the voltages after C50 are all Negative is that part of the B+ (245V supply) line goes into TS8-4 which is also where one side of C50 goes in at as well as R54 and R56 and C3B tie in at, and at TS8-3 which is where the other side of C50 comes out (and also where the other side of the 245V supply comes out to supply the 5AQ5 tube with its necessary voltages) is where all of the voltages end up measuring negative, as for my B- reference its where the black wire coming from the power switch ties to the chassis and to the "chassis ground" for the old C3 can (which is out of circuit), and using that B- reference point is giving me negative voltage readings on the TS8-3 side of C50/245V supply line unless I reverse my probes (positive red probe to B- reference and the black negative probe to the voltage reference point).

Now I don't know how I can make that any clearer than that but I'm telling you that's what's happening to me with this TV.

[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.

[Kevin Kuehn]

Originally Posted by vortalexfan

OK so what I mean by the voltages after C50 are all Negative is that part of the B+ (245V supply) line goes into TS8-4 which is also where one side of C50 goes in at as well as R54 and R56 and C3B tie in at, and at TS8-3 which is where the other side of C50 comes out (and also where the other side of the 245V supply comes out to supply the 5AQ5 tube with its necessary voltages) is where all of the voltages end up measuring negative, as for my B- reference its where the black wire coming from the power switch ties to the chassis and to the "chassis ground" for the old C3 can (which is out of circuit), and using that B- reference point is giving me negative voltage readings on the TS8-3 side of C50/245V supply line unless I reverse my probes (positive red probe to B- reference and the black negative probe to the voltage reference point).

Now I don't know how I can make that any clearer than that but I'm telling you that's what's happening to me with this TV.

Is the bottom side of R54 on your TV connected directly to the left end of R56, or is it connecting to the alternate point Sams shows with the dotted line? If you'll notice there's an X in the B+ line between R56 and R54. That X indicates the B+ point from R56 is disconnected from R54 when the alternate source is used. In any event you're no longer focusing on the audio output issue and the point feeding R54 has no influence on the audio output portion.

[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

Is the bottom side of R54 on your TV connected directly to the left end of R56, or is it connecting to the alternate point Sams shows with the dotted line? If you'll notice there's an X in the B+ line between R56 and R54. That X indicates the B+ point from R56 is disconnected from R54 when the alternate source is used. In any event you're no longer focusing on the audio output issue and the point feeding R54 has no influence on the audio output portion.

The top-side of R56 is connected to the bottom side of R54 which is connected across C3B, which is the point where you were saying that there was a "dead short" earlier when I was telling you that the voltage from there was going from 145V to 22V at pins 5 and 6 on the 5AQ5 tube socket, which by the way, that is how the original C3B in the can was hooked up from the factory, unless you're trying to suggest that somehow this TV was miswired from the factory and somehow managed to get past Zenith's stringent QC standards?

[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.

[vortalexfan]

Originally Posted by Kevin Kuehn

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.

Yes 10,000 pF is the same as .01 MFD but I'm not sure what the voltage is as it's not specified in the Sam's, plus the Sam's calls out specific types of caps by the value given (MFD for paper caps or film caps in the modern world, and mmfd for ceramic disc or mica caps.) I have some .01 MFD 630V film caps but I don't.know if the voltage is high enough, because I know a lot of times ceramic disc caps used in TVs were often times 1kV or higher rated.

[Kevin Kuehn]

Originally Posted by vortalexfan

Yes 10,000 pF is the same as .01 MFD but I'm not sure what the voltage is as it's not specified in the Sam's, plus the Sam's calls out specific types of caps by the value given (MFD for paper caps or film caps in the modern world, and mmfd for ceramic disc or mica caps.) I have some .01 MFD 630V film caps but I don't.know if the voltage is high enough, because I know a lot of times ceramic disc caps used in TVs were often times 1kV or higher rated.

.01 MFD 630V film is fine. We know what the B+ is supposed to be on the detector side, and there should be no B+ on the volume control side.

[Notimetolooz]

Vortalexfan. I've been checking on this thread from time to time and I have gathered up quite a few comments, so this is going to be a long post.
First of all, you are not doing this for money so take a break from time to time, this thread is not going away. If you are working until you are too tired you are going to make mistakes and will not be thinking straight.

You experience with the Meck is an exception not the rule. Take a look at the restoration articles at Phil's Old Radios. Lots of electrical and mechanical problems.
https://www.antiqueradio.org/restoration.htm
Also notice the thousands of posts on this forum. Do you think that if everyone just did a good job of re-capping they would not have anymore problems? Maybe they are just stupid, eh?.

Boo-hoo, school did not cover electronic repairs. Only the repair schools run by a few companies offered repair classes and for a fee. My repair knowledge is completely self taught from reading magazines like "Popular Electronics" and "Radio Electronics" (available online now) as well as books and from experience. I read many posts on the forums even if I don't have any of the units just so I can learn more. Never stop learning.

Comments like "which end of a capacitor to disconnect" shows you don't know much about how electronic components work. Your statement about DC voltage loss across a capacitor is further proof. (Capacitors do not conduct DC current.) I've suggested before that you look to sources outside this forum to learn about how electronics work (like how a tube is biased).
You comments about reversing the meter leads so that the meter would read a negative voltage as positive was nonsense, (if you did that then the positive voltages would read negative), or were you trying to be a smarta$$.

I'm sure Kevin was confused as I was with your "Alice in Wonderland" reports on the circuit measurements. They do not make sense.
When you have results that don't make sense it usually means some of you assumptions are wrong.
You THINK the meter is correct. You THINK you connections are good. You THINK you don't have any shorts. You THINK the new parts are good. You THINK you installed the new parts correctly. Something is not true.

EDIT: Anyway, I've said enough.

[Electronic M]

Vortelex fan is Captain Clock.... He's minded his Ps and Qs better so I haven't said anything, but I've known for years.

If you regress too much to clock mode someone's going to complain and get kicked you off VK again.