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#16
05-19-2011, 10:00 PM
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I have a Zenith out in the shed that I think is from somewhere in the 69-71 era. I would give it to somebody if they were to come get it. Not much different from this one.
__________________
Bryan 
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#17
05-20-2011, 08:48 AM
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#18
05-21-2011, 07:23 PM
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It's here!
I owe my friend Mike big time for helping me get this sucker home. It was in the second floor bedroom of the mother-in-law's and we were both drenched in sweat by the time we got it to the first floor. We manged to get it in between thunderstorms in my '71 Olds Vista Cruiser station wagon-- how appropriate! The model is Y4528 and the chassis is 20YIC38. The CRT is a 25XP22 that is a replacement Sylvania. It test good overall, with the red gun being a little weaker. The chassis is very dirty but appears to be unmolested. I did an initial inspection and clean up. I powered it up slowly on a variac and was rewarded with a a raster and sound  The picture is shrunken and monochrome but obviously the vital organs are good! The EC cans stayed cool to the touch. Marty59 is right, the convergence controls are behind the speaker grille-- cool!Every control in the thing is very dirty so the next step will be to pull the chassis and clean things up. The are photos of when I first got it home, after a little clean up, first raster at 90V, the CRT emissions test (on green) and the raster after some tweaking. The only knob missing in the main tuning knob which shouldn't be too hard to find (I took the other knobs off for transport). I;m really psyched to have my first vintage color set -- and it's a Zenith  -Clark
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#19
05-21-2011, 08:37 PM
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For some reason I had a feeling this was the 20Y1C38 chassis and not the slightly newer 16Z8C50 and I was right. Mine had a a slightly plainer cabinet but you got practically the same set I had when I was starting out with tvs.
Wish I had kept mine. 
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#20
05-21-2011, 10:03 PM
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JCFitz, I just reread your earlier post and you did indeed nail it as a the 20Y1C38 chassis. I'm glad to know that it was (is) a good performer. I'm very pleased that the CRT has useful life left and the the fly and yoke are OK. I'll post more pictures soon.
-Clark
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#21
05-23-2011, 11:09 AM
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I haven't had much time to work on the set but I did finish giving it the once-over. I replaced several weak or shorted tubes, including the burst amp. Each time I was hoping it would restore the color, but no dice. The SAMS for this set is 927-2. Anybody have a scan of this before I shell out $22 to SAMS?
I cleaned the VHF tuner, which is a high quality turret type. The UHF tuning was frozen. I did get it moving but it's still quite stiff. The VHF fine tuning seems inoperative. It's activated by pressing in the spring loaded outer concentric knob around the channel selector. It engages and turns the gear on front of the tuner but it make no change to the tuning. The AFC switch on the front panel also seems to have no effect. I thought that maybe the absence of color was a fine tuning issue but I couldn't get color from my color bar gen when tweaking the output frequency. Clearly, I need to pull the chassis and start looking for bad caps, etc. Cosmetically, I'm really happy with the shape that it's in. The cabinet is cherry veneer and solid cherry and it's in excellent shape. I found a temporary tuning knob that works until I find an original. Here are some more photos: -Clark
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#24
06-03-2011, 09:41 AM
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Thanks to Bryan, I now have the SAMS for this set. One look at the schematic and I realized that in a boneheaded late-night move I had completely missed checking the 6GH8A reference oscillator tube. I had checked every other tube and forgotten to check the most notoriously wretched tube in the set! A quick sub with a 6U8A (I'll put in a 6EA8 soon) and this is what I saw:
  It's got some purity issues, but it's looking pretty good overall. The white speckled noise in the picture is a result of my cheap "RCA" DTV box. And to think that up until now I had been blaming my Philco 49-1140  I suspect its crappy switching PS.Last weekend, I inspected the chassis and replaced several electrolytic and what appear to be paper caps. Here's a shot before I did anything. It appears to be all original.  Those look like paper caps, don't they? I replaced the brown ones. The white Elmenco is rated at 1KV so I'll need to order a replacement for it and a few others. Fortunately, the vast majority of caps are ceramic disc. Next, I'll check the HV and HOT cathode current and adjust the efficiency coil. I'm looking forward to getting this set back in tip top shape and watching some period-appropriate movies on it. They certainly don't build them like this anymore! -Clark
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#26
06-03-2011, 10:47 PM
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You really need the cathode current test adapter socked for the zeniths. What a pita without it.
Replace the white ceramic caps, they get noisy and leaky and cause the vertical to jump. I wish I had seen this, i have the pdf sams...whatever. I also have a bunch of zenith service bulletins. If you have any specific issues let me know and i will see if its addressed. I have 2 sets with that chassis. The HV regulation can be a PITA too. Super robust flybacks though.
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#27
06-04-2011, 09:30 PM
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I sold these new in 1969.
__________________
julian
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#28
06-06-2011, 09:06 AM
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Things continue to improve by degrees. I tested the old caps that I removed and none of them were leaky. But I think I'll go ahead and replace the rest of the paper caps anyway. ctc17-- thanks for the advice. I see what you mean about the HV regulation and measuring the cathode current. I think I'll leave the ceramic caps alone for now since the set is working pretty well. Here are a couple of screen shots from the Anchor Man DVD:
  The vertical size is still inadequate and there is a green to purple hue shift slowly drifting vertically through the picture. I think it's time to change the electrolytics in the PS! Both cans run cool, but I don't want to push my luck. Thanks for the help. -Clark
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#29
06-06-2011, 06:59 PM
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It looks like you need to tweak the convergence.
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#30
06-06-2011, 09:18 PM
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That set will make a nice pic. the elmencos will cause vert jitter. The brown plastic caps may be fine, I dont recall have to replace them. I am pretty sure I have a thread in here on that chassis, it was one of my 1st color sets.
The fine tuning may have loose gear on the little gear that engages the tuning slugs in the tuner. If you can see the gear on the outside turning and nothing is happening in the fine tune then thats it. its an easy fix, but you will have to do some dissassy on the tuner. a drop of super glue will fix it. But do take it apart as trying to glue it in place will surely end poorly. The UHF will need to have the big drum reamed, it swells up and gets stuck. If you have an old school cap tester you can save yourself a lot of needless cap replacement. Just pull one leg and test for value and leakage.
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