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  #16  
Old 01-21-2015, 12:19 AM
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Originally Posted by Electronic M View Post
You traded a fine example of Zenith's first production consumer color chassis...I probably would have kept it if I was in your shoes, but then again my love of Zenith products is such that I save Zeniths newer than some sets I'd leave on the curb.
I did, but it needed a CRT and other things.. It was one of those things that got to be too much.. I must have sunk $800 into it between buying and shipping from Harry Poster, to getting a CRT, that ended up breaking during Greyhound shipping, which took over a year to get money back out of them.. And at least I was able to get more out of them than what I paid between buying the CRT and shipping.. So at least I got some of my money back out of it.. And after all that.. It had to go.. Lost it's charm due to what I went through.. But I think Zenith stuff is much better than RCA, and I do plan on getting another Zenith Roundie or two...
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  #17  
Old 01-21-2015, 05:12 PM
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Great scroe Tom, can't wait to see it light up!
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  #18  
Old 01-22-2015, 02:05 PM
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Great scroe Tom, can't wait to see it light up!
Thanks, I'm looking forward to working on it. From what I seem to recall reading about Sylvania CRTs this set having one is either very good or very bad....IIRC folks here have said that Sylvie CRTs look really awesome when they work, but were not long lived...At least in the rectangular era. I plan to test the CRT and then see what it does on a variac...I've had older stock Zeniths wake up working good so it is worth a try. Depending on what other personal projects I find on my plate during break week I may or may not try to give it a full service once it is home. If not there is always spring break or summer to work on it.


Garry, I do have some tube stereo gear I'd consider trading. I'll try to PM you back with some pictures in the next week or two.
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  #19  
Old 01-22-2015, 07:11 PM
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My Saratoga has it's original 21AXP22, after a Beltron run to wake it up it hasn't missed a beat and looks great.
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  #20  
Old 03-08-2015, 03:18 AM
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I got it today (technically yesterday). The CRT was asleep, but woke up well aside from the blue gun which which is a tad weak and may need a mild rejuv to balance it with the others.

I goofed and damaged the CRT protector cup portion of the back while moving it in to my house. It is fixable, and more importantly the CRT survived it, but I still feel dumb for doing it.

I went ahead and brought it up on a variac. The first time got I sound, and the caps (and one of the 3DG4s) stayed cool. The HV did not work, but I found a clue (a small spark in the HV fuse holder) that led me in the right direction. The 500mA HV fuse was blown, and someone bridged it by wrapping thin wire around (which stopped making contact) it and reinstalling. I grabbed a 250mA fuse (of the wrong mount type thus the red clip lead holding it in) and tried again. This time I got HV, and better yet confirmation that most of the circuits are working right.




You gotta love Zenith build quality, a good ~53 years down the line, and probably a decade of dormancy (judging by the sleepy CRT), and it still works that good with almost no help.
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  #21  
Old 03-08-2015, 01:02 PM
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Wow Tom, that's looking very promising! Nice find in Blonde cabinet! Keep us posted.
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  #22  
Old 03-08-2015, 01:06 PM
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I'm in Love.... OK, Serious Lust... (grin)
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  #23  
Old 03-08-2015, 08:00 PM
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Very promising indeed! Looks like it has a cloverleaf from a newer model. That's one less headache. Hope its an easy restore.

Dave
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  #24  
Old 03-09-2015, 02:34 PM
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Originally Posted by Zenith6S321 View Post
Very promising indeed! Looks like it has a cloverleaf from a newer model. That's one less headache. Hope its an easy restore.

Dave
It don't look like any Zenith convergence clovers I've seen, and the integral purity rings are an interesting feature that I don't think I've seen before anywhere. There seem to be two adjusters per petal present, the black knob appears to be static convergence, but I wonder what the white lever is for....To lock the static convergence knob maybe? The electrical tape splices midway along the leads seem to typify the old repairs I've been finding so far....

Among those old shoddy repairs were replacing the dial light with the wrong type and leaving the metal shroud to bounce around inside the set, dealing with bad fuses by bypassing them, or replacing them with parts that are not of the correct speck.



I think I may have fixed the vertical problems (shrunken bottom, poor linearity, only synched at half frequency) it had by replacing all the bees in that circuit (the others tested fine on my heath C-3)....



....I say may have fixed because it did not let me get full confirmation. I popped the chassis back in, and powered it up to a blank raster that filled the screen and seemed to not be flickering at 30Hz as before so it is looking better. I think the tuner may not have been getting power. I found some bad warning signs elsewhere in the chassis while repairing the vertical, and as I was trying to fix the lack of signal those signs, and the slap shot repairs came home to roost....The PS section has submitted it's formal resignation.
While I was troubleshooting the no RF signal issue I was treated to a 3DG4 light show, and the line fuse blew a fraction of a second before I got to the power switch....The line fuse was supposed to be a 7Amp fuse, but low and behold a 10A was in there, and they even noted that by writing on the chassis.


It would appear this set has had a history of power supply problems. On top of the badly replaced horizontal and line fuses one of the heater fusible links opened and was crudely bypassed. The 10A line fuse modification, I'd guess, was the cause of the insulation melting off all the line wiring except the power xformer leads.
I don't know what to do about the wiring going to the power switch. the leads coming out of it's shielded jacket have melted, and I don't know if I should try to strip the jacket farther hoping the lead inside is okay, leave it as is (with most of the exposed damaged part replaced, and the ground shield lead clipped), or steal a similar (non-zip) cord off a newer VCR or DVD player...



The tube that arced had it's mica wafer knocked up and partially off the cage of the tube so I figured that might have caused the arcing, and tried another 3DG4 in it's place, put a new 7A fuse in, and powered it up again....The result: the heaters of all but the 3DG4s lit, and after a moment I wiggled the 3DG4s until one lit, and as soon as it was warmed up it arced and took out my only 7A fuse.

Since then I've started checking/replacing the lytics in hopes that a shorted one is the cause of the rectifier arcing, but frankly I don't know if that is even the right approach to troubleshooting the issue. The last time I had a similar problem (6X5 in an audio gen) over a decade ago it was solved by selling the unit with the problem (which is not a good solution to this)....Does anyone have any clue what would cause a 3DG4 to arc, have any solutions, or any experience with this kind of problem? I suppose I could try to convert it to silicone diodes as a last resort, but I want to at least try to make it work with tubes again.

The back damage I inflicted consists mostly of the mounts for the neck protector cup, and a small crack to the cup its self.





For more chassis pictures, rummaging around here will yield some.
http://s1095.photobucket.com/user/El...?sort=3&page=4
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  #25  
Old 03-09-2015, 07:29 PM
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I replaced all of my electrolytic and paper caps before I powered mine up, so maybe an electrolytic couldn't reform and is very leaky. One of my 3DG4s heater would not light. I was able to bend (using a thin, sharp awl-like spikey thing inserted into the tube pin side of the socket) the socket pin contacts spring metal to get a solid grip on the tube pins. I have not had a repeat of that problem. I would bet its a combination of a leaky electrolytic cap and only one 3DG4 working resulting in overloading the 3DG4 and toasting it while the cap caused the over-current to pop the fuse. My chassis also had a 10A fuse in it. I am using a 5A slow blow in mine now.

Dave

Last edited by Zenith6S321; 03-09-2015 at 07:34 PM.
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  #26  
Old 03-09-2015, 10:28 PM
Olorin67 Olorin67 is offline
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Must be a pretty good short somewhere to take out a 3DG4... If there are 2 in parallel, wouldn't they need to be pretty well matched tubes to keep the load balanced between the two?
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  #27  
Old 03-10-2015, 05:17 PM
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Well, I tested the two close lytic cans. The 4uF 450V sections all were on their way to being open, and one was a bit leaky so I replaced them all with new 10uF caps. The 80uF 475V sections all tested alright, and I don't stock replacement caps rated over 450V so I left them. The Zenith manual indicates the highest PS voltage is only 410V so I wonder if I could get away with 450V caps.
I swapped the used 3DG4 socket contacts with the unused and tightened them all. I found a couple more 3DG4s in my stash (one was a Zenith brand ), and decided to use them (even though the previous ones that arced test just as good).
I then tried a variac power up again and, this time, got no fireworks. The raster returned and once the voltage was high enough I got the signal stages back.

The vertical stage seems to be working perfectly now.

The focus is poor, there is high contrast video smearing/ringing/ghosting that is adjustable with the fine tuning, and the color is on the far edge of the fine tuning and unstable.

I'm going to go after the remaining can and all the bees, and see what that does.

The burnt looking 11ohm ceramic resistor under chassis between the chassis and the B+ winding center tap has cracked, but still tests spot on, and the set works with it that way. Anybody know the wattage of that resistor so I can find a replacement?
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  #28  
Old 03-10-2015, 08:20 PM
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Its a 20 Watt.

Dave
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  #29  
Old 03-13-2015, 07:31 PM
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Originally Posted by Zenith6S321 View Post
Its a 20 Watt.
Dave
Thanks!

I've replaced all the bees, and it is close to completion. The picture is pretty much at the 'don't need to mess with it no more outside of control tweaks' threshold, but the color does not synch through as much of the fine tuning range as I feel it should so I'm going to test the chroma tubes (and all the other tubes while I'm at it).



There is one defect I'm not sure how to address. Namely the tuner seems to have a blown balun. On it's stock tuner I can get my agile modulator without any thing hooked to the antenna terminals very clearly, but I can barely tune in a DTV box properly connected to the antenna terminals.

This led me to a fascinating discovery...I wanted to try another tuner, since I seemed to recall a similar tuner in my junk tuner box, and after some digging I found what looks like a factory correct UHF VHF tuner combo with space command, and bezel!






Part of me wonders if it is for a later model though since the UHF tuner does not use a tube like the chart indicates, and the bezel is a different color and font wise from what is on it.

There is a part of me that is considering getting the space command parts and retrofitting it to use those tuners....
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