Zenith G2322 "Claridge" restoration

[bandersen]

Starting to go through the pile of TVs I have to restore and decided to start with this Zenith model G2322 chassis 23G22 aka "Claridge"

It has an oddball semi-hot chassis where the top plate is hot, but is insulated from the rest of the chassis. The tubes are series strung with a power transformer just for B+ .





This version has a metal cone 12UP4 CRT which made me nervous as they are often bad. I got lucky though and it test very good


Next up I'll slide the chassis out for a closer inspection.

[nasadowsk]

Oh, was the wacky year porthole with the funky chassis? Yeah, never understood those. I suspect Zenith gave up on portholes in general because, as good a set a Zenith was, the styling was a turn off, as everyone started to have an idea of how a TV “should” look…

Note the UL sticker. Approving everything is nothing new to them…

[bandersen]

This is an early model from 1949. I think they made them until 51 or 52. A bit after everyone else has gone rectangular. Seems like they went their own way with both the electrical and cabinet design. Even had their own FM detector tube (6BN6). Must have cost a bunch in R&D.

[Electronic M]

Originally Posted by nasadowsk

Oh, was the wacky year porthole with the funky chassis? Yeah, never understood those. I suspect Zenith gave up on portholes in general because, as good a set a Zenith was, the styling was a turn off, as everyone started to have an idea of how a TV “should” look…

Note the UL sticker. Approving everything is nothing new to them…

Porthole sets were the logical result of, round CRTs, no measurement standard, and a market starved for bigger screens. You can claim more square inches with a double D mask than a rectangular mask, and even more still if you dispense with the mask and show the whole CRT face.
Around the time Zenith and others gave up the porthole sets larger rectangular tubes were reaching market which made portholes pointless.

I think the idea of the 6BN6 was 2 fold...1.) make something that nobody has a patent on so the difference between paying royalties and receiving royalty payments from other companies pays for the R&D several times over. 2.) Make a tube that is both detector and first audio to reduce tube count and complexity/cost.

[Zenith26kc20]

First time I saw one of those sets the thing that stood out most was the tuner. I was used to seeing the small Admiral turret tuner but this one was impressive!

[Dave A]

I picked up the same set at Kutztown a few years ago all restored. Low contrast now though. I'll be watching this.

[bandersen]

I pulled the chassis yesterday and here's what I found.

• All knobs are present including the five under the door. (I also have the metal back)
• The fine tuning dial string is broken
• The channel selector is frozen.
• The CRT support spring has broken loose because a post broke off the lucite CRT support. (I may have a spare).
• Very little servicing has been done. Looks like only one or two paper caps have been replaced.

Replacement caps?

[AlanInSitges]

Did you decide if the CRT was a replacement or not? I was thinking that it's possible the set was removed from service when the original developed an open in the base and so you've got a relatively low-hour original CRT. Looking forward to find out!

[Kevin Kuehn]

That CRT looks like it's a Sel Son brand. I thought early Zeniths likely came with a Rauland made CRT, which if I'm not mistaken Zenith later owned?

[bandersen]

Correct on both counts. Yes, I do think it is a replacement.

[bandersen]

I finally got around the recapping this beast. The power supply had seen some work and was a bit of a mess. One open power resistor and another had replaced with the wrong value.



I cleaned that up and used adapt-a-caps to replace the 3 multi-section electrolytic caps.


Here's a peak inside the giant tuner.


First power up went well - no smoke and the 5AXP4 test CRT lit up.


I unmounted the PM focus assembly which cleared up the self-focusing 5AXP4 image.


It's mostly working, but I have to max out the contrast and the image is noisy.

[bandersen]

Next I wanted to see what the full sized CRT could do. Here it is all cleaned up.


Gave the chassis a CLR wipe down too.


It lives! Not at all fun to be around that metal cone when it's running.


Normal mode.


Expanded mode


I've swapped all the tuner and IF tubes and rechecked my work. Nothing made any difference.

I'll do a little signal injection next starting at the video amp and working backwards.

[bandersen]

I was able to get a much better image by injecting a composite signal into the grid of the 1st video amp.

Injecting an IF signal into each of the four IF stages seemed to produce a good image as well. I say seem because it's possibly my injected signal was larger in amplitude than a normal signal would be.

Also tried driving the AGC bus directly with a variable DC power supply but it really didn't do much. If I went slightly above or below 0 volts, the image would disappear. Schematic shows 0.1 volts on the AGC bus during normal operation. I'm really not sure what the normal range of this voltage should be.

Finally, went over the tuner again but didn't find any issues.

[Kevin Kuehn]

You could try comparing the tuner signal level at the input to the 1st video IF to what you're directly injecting there. Something needs to give. Maybe use the output of the video detector as the reference so as to not load the IF signal.

[bandersen]

Good idea. I just bought the Sams Photofact for this chassis which has some useful info. For example it says if the AGC delay control is set properly, the signal at output of the detector should be 3.5 VPP during normal operation.

I'll start by going through the voltage and resistance chart for the tuner and IF first though.

I'm also curious about the 470pF cap that couples the output of the tuner to the IF.