1950s or '60s vintage Zenith TVs, Need some info - Page 11 - Videokarma.org TV - Video

vortalexfan · #**151** 11-24-2021, 10:52 AM

So does anyone have a spare power switch/volume control for my 23" Zenith?

The reason why I'm asking is because one of the terminals on my switch/volume control broke off (the ground terminal) its a 2 Meg volume pot with a 1 Meg tap and the shaft is about 3¼" long.

See pictures below for the part number and so you can see what the switch assembly looks like.

dieseljeep · #**152** 11-24-2021, 12:59 PM

Quote:

Originally Posted by vortalexfan

So does anyone have a spare power switch/volume control for my 23" Zenith?

The reason why I'm asking is because one of the terminals on my switch/volume control broke off (the ground terminal) its a 2 Meg volume pot with a 1 Meg tap and the shaft is about 3¼" long.

See pictures below for the part number and so you can see what the switch assembly looks like.

You should be able to solder a wire on the remaining terminal.
You removed the pot, so it's a little easier.

Tube TV · #**153** 11-24-2021, 01:37 PM

X2 on dieseljeep's suggestion. That pot is a rare one and would pretty much have to come out of another Zenith.

Just clean the stub down good and get the area well tinned with solder before attaching a wire and is should work fine.

vortalexfan · #**154** 11-24-2021, 01:53 PM

OK, I'll see what I can do.

old_coot88 · #**155** 11-24-2021, 03:37 PM

X3 on dieseljeep's suggestion. Just be sure the tack area is good and clean so it takes solder quickly. Don't wanta cook the resistive element in the pot.

zeno · #**156** 11-24-2021, 07:00 PM

Or change to a universal 1 meg pot & leave the tap off. It only
there to tailor the bass to the volume. ( boost bass at low vol ).
If its push-pull on / off Malory made a replacement switch.
Depending on shaft it was a KR8M or KR9M.

73 Zeno

LFOD !

vortalexfan · #**157** 11-26-2021, 11:23 PM

OK so I fixed the power switch, and volume control pot and I got the backlights going but I'm still not getting anything out of the tuner, in fact just to check to make sure the tuner wasn't malfunctioning I disconnected the IF input from the TV to the VHF Tuner and hooked the IF input to the composite (yellow RCA jack) on the back of my converter box and all I get is a snowy picture with a very faint hint of video activity on the screen. So it looks like the IF Section of the TV isn't working quite right, I'm not sure if its bad tubes or dirty tube sockets, or a badly out of alignment IF section (from someone twiddling the IF Cans when they shouldn't have.)

Does anyone have any ideas as to what could be causing a dead (or nearly dead) IF Section on the 23" Zenith TV?

Electronic M · #**158** 11-27-2021, 02:01 AM

Quote:

Originally Posted by vortalexfan

OK so I fixed the power switch, and volume control pot and I got the backlights going but I'm still not getting anything out of the tuner, in fact just to check to make sure the tuner wasn't malfunctioning I disconnected the IF input from the TV to the VHF Tuner and hooked the IF input to the composite (yellow RCA jack) on the back of my converter box and all I get is a snowy picture with a very faint hint of video activity on the screen. So it looks like the IF Section of the TV isn't working quite right, I'm not sure if its bad tubes or dirty tube sockets, or a badly out of alignment IF section (from someone twiddling the IF Cans when they shouldn't have.)

Does anyone have any ideas as to what could be causing a dead (or nearly dead) IF Section on the 23" Zenith TV?

That's not how it works let alone a valid test. The IF input takes an AM modulated 41MHz ish RF carrier. The yellow composite video output of a DTV box isn't ANYWHERE close to being that.

If you want to inject baseband composite video you can only do that at the output of the video detector diode in the TV (ideal injection site) or points in the video amplifier chain between that and the CRT.

The IF system will ONLY pass IF signal. It will NOT pass composite video.

vortalexfan · #**159** 11-27-2021, 07:12 AM

Quote:

Originally Posted by Electronic M

That's not how it works let alone a valid test. The IF input takes an AM modulated 41MHz ish RF carrier. The yellow composite video output of a DTV box isn't ANYWHERE close to being that.

If you want to inject baseband composite video you can only do that at the output of the video detector diode in the TV (ideal injection site) or points in the video amplifier chain between that and the CRT.

The IF system will ONLY pass IF signal. It will NOT pass composite video.

Ok, then how do people like Shango and the others that I've seen repairing TVs on YouTube use a composite video signal to diagnose the functionality of the tuner and IF on their TVs when they're working on them?

old_tv_nut · #**160** 11-27-2021, 10:14 AM

They are using a modulator to put the composite signal on a carrier, either RF frequency or IF frequency.

dieseljeep · #**161** 11-27-2021, 12:14 PM

Quote:

Originally Posted by old_tv_nut

They are using a modulator to put the composite signal on a carrier, either RF frequency or IF frequency.

To the O/P: Do you have a tuner subber. It would come in handy right now!

Electronic M · #**162** 11-27-2021, 01:41 PM

Blonder Tongue AM series agile modulators do have IF frequency available. That short coax that connects one port on the back to another port on the back has audio/video modulated IF signal...Shango has used that Blonder Tongue IF output before.

Another source of IF signal (and every other signal you could want for TV) is a B&K 1075, 1076, or 1077 analyst.

vortalexfan · #**163** 11-27-2021, 04:04 PM

Quote:

Originally Posted by dieseljeep

To the O/P: Do you have a tuner subber. It would come in handy right now!

No, I don't have a tuner subber unfortunately.

Electronic M: I've seen those TV Analysts you speak of (both the B & K version and the Sencore version as well (I also think HP made one as well) but they usually want $500+ for them and that's way more than I can afford to pay.

bandersen · #**164** 11-27-2021, 05:02 PM

$500 ? You might be thinking of something else.

The B&Ks routinely go for less than $100. Here's one. I doubt the seller knows how to operate or determine if it's working. Could very well be just fine. Fairly easy to work on if it does need some servicing.
https://www.ebay.com/itm/14424548636...AAAOSw0f5hZupo

I use the Sencore VG91 for the higher (44 MHz) IF.
Likewise, this unit could very well be working perfectly.
https://www.ebay.com/itm/22468660785...4AAOSw9CRhjEbv

vortalexfan · #**165** 11-27-2021, 05:41 PM

Quote:

Originally Posted by bandersen

$500 ? You might be thinking of something else.

The B&Ks routinely go for less than $100. Here's one. I doubt the seller knows how to operate or determine if it's working. Could very well be just fine. Fairly easy to work on if it does need some servicing.
https://www.ebay.com/itm/14424548636...AAAOSw0f5hZupo

I use the Sencore VG91 for the higher (44 MHz) IF.
Likewise, this unit could very well be working perfectly.
https://www.ebay.com/itm/22468660785...4AAOSw9CRhjEbv

Yes, I'm sure, I've looked up quite a few old pieces of test gear and quite a few of them the sellers want $500 or more, especially some of the old signal generators and tube testers and even some of the VTVMs, I think though maybe it's mainly the old Hewlett-Packard, and Hickok gear that goes that high, although I've seen some of the higher end
B & K and Sencore gear go that high sometimes too.
It just depends on the model.