Still struggling… no high voltage and tingling when touching controls

[Madeline12]

Hello… again.

Welp, I’ve replaced all capacitors (both paper and electrolytic) and carbon composition resistors in my Stewart Warner TV from 1951. Booted it up again today with a dim bulb tester which glowed very dimly. Did not get sound nor raster. All tubes, including the picture tube, had a nice orange glow. Upon adjusting the brightness, I felt a slight tingling in my fingers, and unplugged the TV.

At a bit of a loss… the fuse for the flyback was/is intact, though I’ll be testing it regardless. But I’m starting to wonder if possibly the doorknob capacitor near the HV rectifier tube could be the problem… I had assumed the black marks were old flux, but I’m starting to think it’s indicative of another issue… I’ve attached a picture.

Could this be causing the tingling and other issues I described? Any suggestions on how to proceed further?

[Electronic M]

First off if you have discussed this TV on this website before please don't create new topics for it...Pick one of the topics you've made and reply to it when there's updates. It's important to keep all the discussion and info on the set in one place so we don't have to dig for it.

The black looks like it could be black corona dope (insulative paint) the doorknob could be good or bad.... visually there's usually no way to tell unless they're blown in half. Best way to tell is unhook an end (discharge the positive first so you don't get zapped) and stick that end in a shot glass or other small glass container so it can't arc when the set is running.. It's not why the brightness control tingles.

I don't know what model you have to look up the service info, but there are 2 kinds of TV power supplies transformer and hot chassis. Hot chassis sets tie one of the 2 wires of the unpolarized cord to chassis and depending on which way you plug it in the chassis and any exposed metal on the cabinet could be at 120VAC (most makes tried to insulate the metal connected to chassis to prevent touching it but whether the safety bits are still present and good who knows). Transformer sets aren't "supposed" to give you a tingle but can...if the transformer primary insulation fails the chassis can get hot, even if everything is working there's sometimes chassis to cord bleeder resistors that are designed for bleeding excess charge between the chassis and line back to line.... the bleeder resistors can give you a tingle but are designed to limit current to non-harmful levels.

Do you have absolutely no sound?... No static, no crackle in the speaker when changing channels or rotating the volume knob from stop to stop?
If so you need to get the schematic, and a DMM, figure out where to measure the B+ voltages and check them. I suspect your missing one or more B+ voltages or that they're more than 20% below spec (which is bad). The heaters run on the A power supply and it's very easy to have A but no B.

Now is the time for voltage checks and troubleshooting, not firing the parts cannon.

[Madeline12]

Originally Posted by Electronic M

First off if you have discussed this TV on this website before please don't create new topics for it...Pick one of the topics you've made and reply to it when there's updates. It's important to keep all the discussion and info on the set in one place so we don't have to dig for it.

The black looks like it could be black corona dope (insulative paint) the doorknob could be good or bad.... visually there's usually no way to tell unless they're blown in half. Best way to tell is unhook an end (discharge the positive first so you don't get zapped) and stick that end in a shot glass or other small glass container so it can't arc when the set is running.. It's not why the brightness control tingles.

I don't know what model you have to look up the service info, but there are 2 kinds of TV power supplies transformer and hot chassis. Hot chassis sets tie one of the 2 wires of the unpolarized cord to chassis and depending on which way you plug it in the chassis and any exposed metal on the cabinet could be at 120VAC (most makes tried to insulate the metal connected to chassis to prevent touching it but whether the safety bits are still present and good who knows). Transformer sets aren't "supposed" to give you a tingle but can...if the transformer primary insulation fails the chassis can get hot, even if everything is working there's sometimes chassis to cord bleeder resistors that are designed for bleeding excess charge between the chassis and line back to line.... the bleeder resistors can give you a tingle but are designed to limit current to non-harmful levels.

Do you have absolutely no sound?... No static, no crackle in the speaker when changing channels or rotating the volume knob from stop to stop?
If so you need to get the schematic, and a DMM, figure out where to measure the B+ voltages and check them. I suspect your missing one or more B+ voltages or that they're more than 20% below spec (which is bad). The heaters run on the A power supply and it's very easy to have A but no B.

Now is the time for voltage checks and troubleshooting, not firing the parts cannon.

I apologize, still a little newer and didn’t feel the past threads provided any insight much. Will do so from now on.

The TV is a 9121A. The chassis is not hot.

I am also noticing that when discharging the picture tube, the anode cap typically pops out easily without spark when applying a screwdriver + resistor. Not sure if that’s of concern, but thought I’d add.

Previously, I’d get crackling in the speakers prior to replacing all the resistors and deoxidizing the pots, but beyond this no sound. No static, radio, or anything else.

Again, I apologize for the additional post. Happy to share the schematic below (that was also shared with me). I have series A-C-D:

https://drive.google.com/file/d/1_EZ...N31OaxzqH/view

[Yamamaya42]

Sorry, the file you have requested does not exist.

[Madeline12]

Originally Posted by Yamamaya42

Sorry, the file you have requested does not exist.

Sorry about that, did the copy and paste of the shortened URL from video karma. Should work now

[Tube TV]

The tingle sounds like bleed resistors. Meter it out and see how many volts and that there is no amps. I have seen them measure as high as 80 volts but no amps. (Should be only a few milliamps max). Unsolder the primary transformer leads and measure between the transformer primary and the chassis. The reading should be very high 500k , 1 meg ect.

Like Electronic M said that black stuff looks like Corona dope and I wouldn't be concerned about it.

As for the anode cap, consider yourself lucky that you have one that comes off easy. Some are difficult. As for no spark at discharge. In 30 years of servicing TV's I still have never seen one spark, but I still discharge just to be on the safe side. This is not the issue.

At both rectifiers and check the ohms of the secondary windings you're looking for 12 ohms between the points shown on the schematic. Also 70 ohms at the choke.
Check the polarity of all the electrolytic caps you've replaced. Check that nothing is touching. Then start checking DC voltages with the set on starting with the rectifiers and move forward.

[Penthode]

If you have tingling, I would suggest you wear rubber sole shoes when standing on the concrete floor.

[Zenith26kc20]

I have a Zenith 25NC33 that used to more than tingle when I touched any knob.
I had a balun short connected to VHF in and blow the balun in the tuner. It had to have the black wire from the power transformer disconnected or it would blow one of the voltage doubler caps. I finally found the power transformer had a short primary to chassis. Replaced it and no more problems. I would check primary to chassis, secondaries to chassis and primary to secondaries for a short. I would think lightning caused my problem. It's worth a try.

[Yamamaya42]

Replacing the power transformer is no tall order.

[Electronic M]

Originally Posted by Yamamaya42

Replacing the power transformer is no tall order.

I'd just grab a 500VA isolation transformer and leave the original if it's only fault is lack of primary isolation...

[Penthode]

The tingling is normal for sets of this vintage if you are standing barefoot on a concrete floor. In a living room environment there will be no tingling because you will be standing on a carpet.

If you are experiencing a "tingling" can you explain where you think the current is flowing which creates the tingling?

If still in doubt, you could measure the leakage from the power pins to the chassis. And to confirm it is the the bypass capacitors, you could try disconnecting them and see if the tingling disappears. If so you could reduce the capacitor value at the expense of introducing more noise into the mains supply. I no longer think that is a big deal with all the little switch mode power supplies which proliferate the average household these days.

[Yamamaya42]

Or, it could be something as simple as the wrong safety capacitors in the input line, for example if it had .01uf caps it it when it was built, do NOT put the same value in again, it can give you a slight shock if they leak, the have much safer lower value x2 safety capacitors now that are made for that job.

not sure what you have in yours. but here is info
https://www.justradios.com/safetytips.html

it's for Radios, but it applies

[Yamamaya42]

Looking at the schematic, it shows .01uf caps on the input line, those are too big by standards now, as mentioned above, the right type safety capacitors will work much better, also see a 270k resistor on the switch side, this might be an issue, not sure, does it make any difference if you turn the power plug around?
And of course do check resistance between primary and secondary on the power transformer, because of that resistor, it should be 270k with the fuse in, and almost infinite with the fuse removed.

[Zenith26kc20]

The safety caps will put around 60 volts AC on the chassis. Turning the plug around may help but 220K is not going to stop the capacitors as acting as a voltage divider.
Quick and dirty, unsolder them and the resistor and see if the tingle goes away.
And I agree, finding a replacement transformer could be a nightmare.

[Madeline12]

Wow, this thread got a lot busier since I last checked!

I am wearing electrician boots on concrete floor when I tested this and sensed tingling.

I had tripled check the polarity of all electrolytic capacitor, and all were correct.

I did take a multimeter to the power supply and found none of the primary, secondaries, HV, etc. were open. I recently acquired an oscilloscope (albeit, unknown if it works, but hoping it does or if I can repair it relatively quick), so hopefully that may be of assistance if I am successfully.

I have since moved and don’t have immediate access to the tv, but I will this upcoming weekend. I will do my best to update and follow the information provided by all you helpful people on this site. Can’t thank you all enough.