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

[vortalexfan]

Originally Posted by Kevin Kuehn

What Notime was suggesting is that you're struggling to understanding the fundamentals(small stuff), yet you so desire to fix very complex problems, things that required advanced troubleshooting skills even back in the day. Electronics is simply one of those disciplines that if you don't "learn yourself" the most basic elements, you may never be able to find your own way. There simply is not a canned answer for many of the problems you'll encounter, not even in advanced text books of the past, so you need to become quite well versed in the basics in order to find your own way. The B&K 1076 I mentioned earlier - being it's old, all tube, and quite a complex piece of test equipment, I fear if it has stopped working when you get it, or stops working at some point, you will just have wasted the shipping money on a useless paperweight. No one here is scolding you, but there simply is not a way for any of us to help you advance beyond your own willingness to teach yourself.

And I did finally figure it out on my own. I realized that some of the electrolytic caps that I didn't replace yet at that point were part of the deflection circuitry so I decided to finish replacing the electrolytics and sure enough it fixed the issue.

As for the Magic Smoke escaping issue I figured out it was the output transformer had gotten smoked, because when I went to test it after my initial recapping (replacing the easier to access electrolytics and paper caps) to check my progress with getting some sort of recognizable raster that wasn't deformed/collapsed looking, I forgot to connect a speaker to the output transformer and I think that's what the magic smoke came from.

Thankfully i have some spare Zenith output transformers that I had salvaged from that old Zenith Console Stereo I picked up for parts, but they have three wires on the primary side rather than just two wires like the one that's in there right now that had burned up.
They have a brown, blue and red wire lead on the primary side as opposed to just the red and blue wires on the original transformer.

If I were to use one of the replacement output transformers that has the three wire leads on my small Zenith TV in place of the burned out transformer, would I just cut the brown wire off the transformer and use just the red and blue wire leads, like how it was done on the original output transformer?

Any help with this issue would be appreciated.

[vortalexfan]

OK so I figured out that the escaped magic smoke that I saw when I tested out the TV the other night before I finished recapping the Zenith Bugeye TV (the smaller 17" Zenith) was from the output transformer which I accidentally smoked because I forgot to hook a speaker up to it when I was testing it.

I have a couple of Zenith output transformers that I had salvaged from that old Zenith Console Stereo that I parted out but I'm not sure if any of them will work in place of the original output transformer in this TV, because they have 3 wire leads on the primary side instead of 2 like the original did, but also the transformer is slightly larger than the original transformer.

What do you guys think? See picture below to see what the replacement output transformer looks like compared to the original.

[old_coot88]

The speaker being disconnected should not hurt the xfmr UNLESS the audio was blasting at such a high level that the xfmr was arcing inside (highly unlikely).

Did you take an up-close whiff of the xfmr? If it's zorched, there'll be a scorched smell coming from it (per the old techie proverb "the nose knows"). And did you verify continuity of both windings with an ohmmeter? The primary should be a few hundred ohms, the secondary a fraction of an ohm.

More than likely the smell was from some other component, probably a resistor that got cooked.

[Kevin Kuehn]

The problem with resistors is they're so small they can't pack very much smoke in them at the factory. So it makes better sense that the smoke came from something significantly larger.

[vortalexfan]

Originally Posted by old_coot88

The speaker being disconnected should not hurt the xfmr UNLESS the audio was blasting at such a high level that the xfmr was arcing inside (highly unlikely).

Did you take an up-close whiff of the xfmr? If it's zorched, there'll be a scorched smell coming from it (per the old techie proverb "the nose knows"). And did you verify continuity of both windings with an ohmmeter? The primary should be a few hundred ohms, the secondary a fraction of an ohm.

More than likely the smell was from some other component, probably a resistor that got cooked.

There was no audio coming from the speaker and the audio output tube was barely warm to the touch, also the output transformer's primary leads measured a little over 500 ohms and the secondary leads measured about 0.6 ohms, which didn't seem right because the Sam's specs the transformer primary as 10,000 ohms and the secondary as 3-4 ohms.

[Electronic M]

Originally Posted by vortalexfan

There was no audio coming from the speaker and the audio output tube was barely warm to the touch, also the output transformer's primary leads measured a little over 500 ohms and the secondary leads measured about 0.6 ohms, which didn't seem right because the Sam's specs the transformer primary as 10,000 ohms and the secondary as 3-4 ohms.

Is that the spec from the parts list or the schematic? Those look like parts list specs which are AC impedance NOT DC resistance. It's possible for a transformer to have a 10K AC impedance and a 500 ohm DC resistance.

What I'd do is hook up a good 4 ohm speaker and connect an audio frequency test generator to the grid of the output tube (test the tube before this test to confirm it's good) and see if it comes through to the speaker. If the the tube is good and voltages on the audio output tube are within %30 of spec and it doesn't pass audio then the transformer is bad.

[dieseljeep]

Originally Posted by vortalexfan

There was no audio coming from the speaker and the audio output tube was barely warm to the touch, also the output transformer's primary leads measured a little over 500 ohms and the secondary leads measured about 0.6 ohms, which didn't seem right because the Sam's specs the transformer primary as 10,000 ohms and the secondary as 3-4 ohms.

Sams specs are impedance ratings and not DC resistance.
The ratings you state seem to be right. Compare it with another transformer.

[vortalexfan]

Originally Posted by Electronic M

Is that the spec from the parts list or the schematic? Those look like parts list specs which are AC impedance NOT DC resistance. It's possible for a transformer to have a 10K AC impedance and a 500 ohm DC resistance.

What I'd do is hook up a good 4 ohm speaker and connect an audio frequency test generator to the grid of the output tube (test the tube before this test to confirm it's good) and see if it comes through to the speaker. If the the tube is good and voltages on the audio output tube are within %30 of spec and it doesn't pass audio then the transformer is bad.

Ok, well I for sure checked all resistors in the area where I saw the smoke come from and all of the resistors tested fine yet, as for the output transformer goes what would happen if you hooked an 8 ohm speaker to a 4 ohm output transformer? I'm asking because the speaker I was using to try and test the audio output on the TV was an 8 ohm 30 watt bookshelf speaker.

UPDATE: I figured out where the smoke really came from, it came from a replacement 470 Ohm 1/2 Watt resistor I had replaced in the TV that either got really hot or got smoked because its kind of charred looking in the middle of the resistor, and the original 470 ohm 1/2 W resistor that was in there which was an old carbon composition resistor broke in half on me when I was trying to unsolder it from the old can capacitor terminal it was attached to originally when I was installing the replacement cap, (the original carbon composition resistor also looked quite charred looking as well) so I wonder if that capacitor was under spec'ed for what its intended duty was in the circuit?

[old_coot88]

Originally Posted by vortalexfan

...what would happen if you hooked an 8 ohm speaker to a 4 ohm output transformer?

A slight reduction in volume.

[vortalexfan]

Originally Posted by old_coot88

A slight reduction in volume.

OK, but it wouldn't of caused a no audio issue?

[Kevin Kuehn]

I suppose you've already measured the DC voltages on the pins of the Audio output tube, and verified they are close to what Sams calls out.

[Kevin Kuehn]

Originally Posted by Kevin Kuehn

I suppose you've already measured the DC voltages on the pins of the Audio output tube, and verified they are close to what Sams calls out.

FWIW when you do the above you'll need to have the output transformer connected in the circuit. In case you haven't figured it out, the Sams for your Bug eye model Y1814YU is in Sams 333 folder 17.

Link to the center section of the schematic, where the audio output is at the top right.
https://live.staticflickr.com/65535/...ce52b32e_k.jpg

Link to right Page of schematic.
https://live.staticflickr.com/65535/...660e33e3_k.jpg

Link to left page of schematic.
https://live.staticflickr.com/65535/...16ea5667_k.jpg

[dieseljeep]

Originally Posted by vortalexfan

And I did finally figure it out on my own. I realized that some of the electrolytic caps that I didn't replace yet at that point were part of the deflection circuitry so I decided to finish replacing the electrolytics and sure enough it fixed the issue.

As for the Magic Smoke escaping issue I figured out it was the output transformer had gotten smoked, because when I went to test it after my initial recapping (replacing the easier to access electrolytics and paper caps) to check my progress with getting some sort of recognizable raster that wasn't deformed/collapsed looking, I forgot to connect a speaker to the output transformer and I think that's what the magic smoke came from.

Thankfully i have some spare Zenith output transformers that I had salvaged from that old Zenith Console Stereo I picked up for parts, but they have three wires on the primary side rather than just two wires like the one that's in there right now that had burned up.
They have a brown, blue and red wire lead on the primary side as opposed to just the red and blue wires on the original transformer.

If I were to use one of the replacement output transformers that has the three wire leads on my small Zenith TV in place of the burned out transformer, would I just cut the brown wire off the transformer and use just the red and blue wire leads, like how it was done on the original output transformer?

Any help with this issue would be appreciated.

It's fine for a temporary test, just use the red and blue wires.
I never cut the leads from a transformer, just insulate it with tape or ??.
Tack it in and with a speaker connected on the secondary and try it!
Replace the 470 ohm resistor with at least, a one watt unit.

[vortalexfan]

Originally Posted by Kevin Kuehn

FWIW when you do the above you'll need to have the output transformer connected in the circuit. In case you haven't figured it out, the Sams for your Bug eye model Y1814YU is in Sams 333 folder 17.

Link to the center section of the schematic, where the audio output is at the top right.
https://live.staticflickr.com/65535/...ce52b32e_k.jpg

Link to right Page of schematic.
https://live.staticflickr.com/65535/...660e33e3_k.jpg

Link to left page of schematic.
https://live.staticflickr.com/65535/...16ea5667_k.jpg

I've already got a physical copy of the Sam's for this TV, as for measuring the voltages at the Output tube pins no, I haven't done that yet, I will do that now.

I have a signal generator but not an audio generator, would a signal generator work the same way?

[vortalexfan]

Originally Posted by dieseljeep

It's fine for a temporary test, just use the red and blue wires.
I never cut the leads from a transformer, just insulate it with tape or ??.
Tack it in and with a speaker connected on the secondary and try it!
Replace the 470 ohm resistor with at least, a one watt unit.

Replace the 470 Ohm resistor with a 1W unit even though the Sam's calls out a 1/2W in that position?