Craigslist Zenith Score!
 

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I picked up my first all tube Color set today, from a seller in the Collinwood neighborhood of Cleveland. It's a 1966-67?? Zenith, still running on almost all of it's original tubes. On top of that, I found something interesting upon taking the back off the cabinet. There was what appears to be a space command tuner laying loose next to the chassis. It appears that the volume control also has a plastic gear drive attached to it, with happens to be cracked in two. The motor and space command receiver are missing, however. I'm guessing that the space command broke at some point in the past and was simply replaced by a manual tuner. Upon first power up, HV was very low and the picture bloomed and went out of focus as the brightness control was increased. A new 3DJ3 took care of that problem. The Electrolytic cans stay nice and cool, too! I'll post the model and Chassis numbers in a little bit.
Sorry about the poor quality iPhone pic. I'll post better photos soon.
Also, How hard would it be to find the missing Space Command components?

This was the extra tuner I found laying in the cabinet.
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sweet. cool cabinet. are the reds weak or is it just the programming (looks a bit weak to me)?

Kewl score !

It's the lighting and my iPhone camera. CRT tests strong on all three guns.

Well, I have a problem. Went to turn on the set this morning, and a raster never appeared. I can hear some HV whine and audio, but nothing else. The set played fine all last night. Where would be an obvious place to look for a problem like this? I checked the HV rectifier, horizontal output tube, and damper, all tested fine.

Can you hear the high voltage "crackle" when it comes up? If so, look for the video output tube and see if it is lit. I have a similar chassis, different model that gives a nice picture.
Also, check your focus rectifier. I am not sure but on some sets no focus voltage can cause no raster.

Do you mean the crackle as the picture comes up and into focus, If so that's what I'm not getting. I'll check the focus rectifier, it's the green "stick" rectifier, correct? Just test it as a diode?

use a HV probe to monitor the CRT anode voltage

is the HOT red plating? wiggle the HOT and the horz osc tubes. hold a neon bulb near the plate cap of the HOT (I have one mounted to a small plastic stick).

I would pull the HOT plate cap off, check for B+, if that checks then I would put it back on and check the HOT grid for about -50v, screen voltage of around 150v. Also check the cathode current of the HOT.

This is where a tv analyst like a B&K 1076 comes in real handy.

you cant check the focus stick like a reg diode. You can just check the focus pin of the CRTwith either a meter like a simpson 260 on the 5kv setting or just a reg HV prob, the same as used in the CRT anode. Check to see around 5kv

The HOT is not red-plating, and has a mild blue glow. I don't have an HV probe right now, but will borrow one from a friend. Neon lamp lights near the plate cap of the HOT.

I would try a new HV rectiifier tube, assuming the HV is not present.

I'll give that a shot, though I just replaced it with a NOS one last night.

From looking at your pictures that set never had space command. Sorry.

Bingo. The "new" one i installed yesterday must have been a dud.

If so, what was the original purpose of the extra tuner and bracket on the top of the cabinet which it was mounted to? Was it just a different type of manual VHF tuner that failed and was replaced with a similar one?

Several things, Zenith used power tuning on their remote sets back then so there would not be anyway to mount a VHF knob on the front of the set. They also didn’t use a motor drive on the volume control it also most likely would be behind a door with the VHF fine tuning. That tuner does not appear to have ever been setup for power tuning. Even if it was just missing the motor. There are other ways to tell as well.

Thanks for the information. I saw the gears and got all excited. The extra tuner will remain a mystery I guess. I'd like to get it working again, as it had lighted channel numbers that appeared from behind the smoked plastic control panel faceplate. At some point a tech must have pulled the original tuner out and installed a new one with a standard knob.

Ahhh....so YOU were the one ;).

I was planning on traveling from Buffalo to snag it, but you walked in with double my offer. Hey, I'm just glad that a VK member got it :) Great set!

Sorry about that. I haven't seen a tube color set on Cleveland craigslist in over a year, and the last one i tried picking up, the seller ended up flaking on me. I jumped on this one when I got the chance.

Well, I feel like an idiot. This set was meant to use a 3A3 HV Rectifier. If I would have looked more closely at the cabinet tag in the first place I would have figured that out about two days earlier. When I opened the HV cage the other day, a 3dj3 was what I found, so that's the tube I replaced it with. That explains why every 3dj3 I put in ended up glowing blue in a few hours, or less. I've had the 3A3 running in the set for close to six hours. So far no problems.

By the Way, this set uses a 23XC38Z chassis.

The list of subbed tubes keeps on growing. A 6LB6 had been subbed for the 6JS6 HOT, a 6HV5 for the 6HS5 HV REG, and the aforementioned HV rectifier. Since I swapped out the tubes with correct replacements, I've had no problems.

I may be wrong about this but some zeniths provided for a HOT swap with a jumper change. there should be a tag on the jumper block with which connection to make on those two tubes. IIRC it changes the source and voltage of the screen on the HOT.

The only jumper located anywhere near the HOT is for increasing horizontal width. In any case, I tested the 6LB6 I pulled from the set and it was really weak. Set played beautifully tonight with the 6JS6C installed. I just ordered an HV probe. I figured I'll need one now that I own a set like this. Also, does anyone have any service data for a 23XC38Z chassis? It'd be nice to have it just in case.

Also, 6-19-66 is stamped on the HV cage. Would this be a production date code for the Chassis?

some of those subs are ok.many of the 12 pin sweep tubes will sub no problem.the reg and damper in many zeniths must be a pair specified on the layout.iirc its about the warmup time.making sure the reg is ready before the damper warms up.

The set is now working really well, a weak 12HL7 video amp and three weak 6KT8's later. This set appears to have a lot of original tubes.

The Tuner and IF tubes were also original, and really weak. Replacing those took care of smearing when white text appeared on screen.

The reason for the specific regulator/damper pairings in the Zenith
color sets was that the two tubes heaters are wired in series. Probably a safety feature to keep the HV from coming up if the reg. was pulled.
The heater currents have to be matched in a series connection or one tube will light up real bright and the other hardly at all. The two pairings are equivalent tubes with different heater current ratings.