Zenith Roundie
 

Picked up this Zenith Roundie this evening. Thanks to DaveWM I was able to determine that the CRT was good. My tester really let me down on this one. It showed no emissions on any gun. I called Dave and he guided me through a simple test that in this case proved the CRT was good. Thanks Dave.

That's a nice looker, what chassis does it have? It looks like a late 1964 model. Great score!

John, could you or Dave share the details of this test for everyone's benefit? It could prevent other good CRTs from getting tossed.

His CRT tester was showing no emissions. The set had been in sevice, but he did not have a test signal to see the actual picture. It did have a raster.

I just told John to turn the screens down and then one by one turn them up, they each produced a bright raster. Not very scientific, but if your tester is showing zero emissions then I presume its the tester under the circumstances.

Thanks for the reply Dave. In this case the tube was known to have a picture, thus had to have some emissions.

I was thinking perhaps you had a test for a CRT not in a working set.

right. I figured there had to be an issue with the tester, so the next best thing was did each color make a good raster, with out a weak color (generally red).

I have done this before where I was caught without a CRT tester AND the owner had already been turning it on "to test it". Like I said its not very scientific, and not really checking for cut off, but in a pinch...

Of course its better to not turn on a set if its been idle, like the guy with the moto wants desperately to do.

Hhmmm.....I gonna' make a fun guess here and say it's either a 25LC30 or an early version 24MC32. The 21FBP22 dates it a little bit but I could be wrong!

Yeah, that looks like trouble in the making...

If the guy with that Motorola is so worried about getting top dollar, he should contact someone familiar with 15GP22 CRTs and have them go to Utah and check it out. Then share those results here and with the ETF crowd, and auction it off.

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Are you guys talking about the guy with the '54 Westinghouse? Or, did I miss a Moto somewhere around here....:D

Sorry, Mark. You are correct, the Westinghouse.

No apology needed, I just thought there was something I missed!:D

Dave's right, My tester didn't work at that moment. I think it didn't make good connection on the appropriate pins. I couldn't get my meter to come up to the cut off line. On my tester, a B&K 465, I first set the heater voltage, in this case 6.3 volts. Then I set the G1 to 40. Next I set the function switch to cut off and use the G2 control to set the meter at the cut off line. Lastly I switch the function switch to emission and see what the meter reads. I couldn't get any of that to work last night so I assumed the CRT was not emitting although it was clear that the filaments were working in all three guns. Thinking what harm could there be if the CRT was dead anyway so I turned the set on and the set had a great raster!

That's when I called Dave and he walked me through the test he described above.
When I got the set home and set up the tester again everything worked fine. I got an emissions reading of 880 on the red gun, 820 on the green gun and 820 on the blue gun. Since it had already been turned on yesterday with no ill effects I turned it on again this morning and here are some screen shots.

virtually the same set I have. Do you have the legs?
A real sweetie of a set when working right and a workhorse to boot!

no legs on this one

you are pretty close to have it working well. check that contrast adj, if it does not very much, then you prob have an open cap in of the cans, the 200uf IIRC.

A quick test will be to tack in a 200uf + to the center of the contrast pot, neg to ground. just use some jumpers for a quick check. the blurryness is a result of the cateract.

Looks like you're off to a real good start!

Hard to believe it works so well already-great score!

Joe actually pretty easy to believe, I have had several zeniths, most work with no or only very minor work. They were very very well made. Most of my zeniths have all the orig caps. They are a bit harder to work on since the point to point id done with those solder cups which can be bit of a problem getting the parts out and in again (I prefer PCB's) but at least there is no heat damage to worry about. Also the flyback seem stouter than most.

I have had the video out cathode bypass cap (contrast) go open on some, and now and then the AGC has a little black and red electro that will go open, but for the most part I think its best to leave them be and fix when something goes wrong.

The picture on this set just keeps getting better as it comes back to life. I ran it a couple hours last night and the color just keeps improving. I can't get into any repairs this week but next week I should have some time to do it.

Two more screen shots

wow, that is looking good. The only thing you may want to check is the AGC setting and confirm if the contrast control is working well. the AGC will help with contrast some. If the contrast control does little then its prob that cap I mentioned, but frankly it looks fine to me as is.

Kinda too easy eh :D

Oh and for fun when you get the HV probe double check the voltage, but I think you will find it all works just fine as is.

Mine is just like that only no UHF and it has a metal cabinet. It actually produced a BEAUTIFUL picture when I brought it home out of over 20 years dormancy. After some play time the color went black and white and I haven't touched it since. A good fellow here sent me a crystal that supposedly is known to go out and cause this. I know there are many other things that could cause it, but I hope the common issue is the one because I sure would like to see that beautiful picture again.

I have often thought it amazing the color quality that some of the early color sets produce. Mine also had what looked like some horizontal distortion on the far left side of the picture. I know that it really is screaming for caps and it would be worth it to do. I've never redone a color set and I am a bit skittish as there are so many things that must be adjusted or aligned; more so than the old black and whites sets. I don't have any of the alignment equipment and all of our TV shops are gone, so if I do the job, I will hopefully not have to mess with the convergence board and such and stick with the lytics and the paper caps in the horizontal and high voltage areas to begin with at least. Supposedly the HV and horizontal are the circuits to watch out for.

Talking about alignment, I watched a video today that made it look easy but I'm sure a service manual would help a lot. I think the manual would take you step by set through the process. Right now I'm getting some tubes that I need for the set that will hopefully improve the sound quality. I don't think I'll be replaceing any caps unless they just call for it. Here's the video.
http://www.youtube.com/watch?v=o8eK2CyDmiY