Tip on the horizontal hold: the control is a coil, not a pot....So the stop is the knob's pointer hitting the metal tab in the pencil box. To get more range pull the knob out past the point where the pointer hits the stop then turn it some more. The knob should have a hex shaft so you could set it up so the pointer is at mid mech range at the center of the electrical sync range. I can't remember changing caps having much effect on H hold range in Zeniths.

biggest issue with Zeniths was the coil forms, the plastic is an issue, other than that they pretty much just work, even with the old caps. Sometimes you may find a cold solder joint on a tube socket, IIRC the video out on later models had this issue, maybe not a prob on the roundies, but it would manifest as a overly bright pic esp near the bottom, solved with a smack of the cabinet. A good socket cleaning of all the tubes will get you 90% of the reliability back, and that's assuming it was stored where corrosion could take hold. Zeniths were built to last, the other plus is the HV was very robust with no flyback issues.

Best of all is no printed wiring, no production shortcuts. You can run a Zenith all day without cooking it to death.

Yea the RCA PCB's on high hour sets are frequently smoked.

Unfortunately that was also true of clone sets by Philco sylvania magnavox GE Emerson etc. no wonder zenith got such a jump on everyone else🙂

The metal control panel door definitely isn't as tough as they made the chassis and such. I wish I knew where to get a better one. Those screen shots look good. Did you have to do dynamic convergence work? Hope I didn't miss the answer to that in this thread. Just curious as mine needs it. I can live without it, but the Zenith's make such a nice picture, it a shame to go without.

Got a test pattern gen, hex diddle stick, and a chassis #? You'll need a gen with cross hatch to do it, and a diddle stick. I've got some Zenith issued color service manuals....It would be a trivial matter for me to post pics of the convergence procedure documentation for your chassis (or the closest one I have lit for).

Most deltagun sets have the same convergence procedure and some makes/models were kind enough to essentially number controls to walk you through the procedure.

I haven't done anything yet except replace three tubes. Guess I got lucky :) New caps should arrive today.

New caps from Digi-Key have arrived and they were very well packed.
I went with them because they have a decent selection of 500v caps. I wanted them to replace the six original 475v rated caps.

All the caps are rated for 105C and long life. The two caps in the B+ voltage doubler are also rated for high ripple current.

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The main B+ runs at 330 with a voltage divider tapped for 235 and 120 - all well below 475.
Then it occurred to me it uses a solid state rectifier so B+ will be available instantly while the tubes are still warming up.
I expect B+ runs fairly high until the tubes start conducting.
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Two of the caps are 4uF and the only 500V+ ones at Digi-key below 10uF are surface mount.
10uF would probably work just fine but I decided to give these 3.9uF SMDs a shot. I think it'll be easy to solder on extension wires.

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I'm a little wary of pulling the chassis, but it needs to be done. The width slowly grows about 20% over 15 minutes from a cold power up, controls are dirty and some HV arcing persists. A recap, cleaning and new tubes should improve things.

If cleaning does not cure the arcing problem, You may have to replace all of the hi voltage wires in the cage. Inc the wire to the crt anode. Had to do this to two of my Zenith color set's. The color circuits are working good so, DO NOT touch the coils in the color circuit. They get brittle from heat and will break if the core is turned to adjust. Another problem is you may see some slight bars in the picture on a black screen. I was not able to track down that problem. Not that noticeable, And most people would not even see them.
Ed

the set used mylar caps, so why are you doing a full re-cap? Slow width is a weak horizontal output tube.

He's right you know... the HO tube is just getting tired.

I was thinking it was electrolytic slowly forming up. I can check that by monitoring the B+. Wasn't planning on replacing all the caps - just the stripped bumblebees looking ones. Are you sure all the caps are mylar?

I tend to change the bees and the tubular white ceramic cased ones...I've found bad or dying ones in sets of this vintage so if I'm in there for something I tend to change those.

Be watchful of those surface mount caps. Mitsubishi sets used them everywhere and the capacitor plaque was terrible. Just watch for goo coming out after a while.

For the most part, what Tom said.
Most are Mylar tho. It's not like the older sets you're used to where you have to change ALL of those horrid wax caps. Sets from about 1963 on up are pretty stable. You won't have to worry about capacitor plague. That was mainly a "Jap" set thing.....

I do in fact have an old RCA dot bar generator and a diddle stick. I would need to check the stability of the generator as I seem to remember it being a bit persnickety last I used it. Someone rigged the end of the input with a bunch of resistors in a haphazard way for some reason. Anyway, yes I would like to do that. I think I have the Sam's folder in .pdf for the set. Sorry, it's just been sitting for a few years waiting for the "significant" to vacate. :thmbsp:

"Another problem is you may see some slight bars in the picture on a black screen. I was not able to track down that problem. Not that noticeable, And most people would not even see them."

I've always noticed them too, quite common on roundie Zeniths. About three light/transparent vertical bars, no foldover, just there!

Interesting you mention that. Mine has them too. They are not a problem, but just there.

There is no way i would use those surface mount caps unless you want to see a failure in a day or so. throw them in the garbage.

Why exactly ? Just because they are surface mount ? They'll work just fine.

Justradios dot com has 4 mfd@500 volts. I'm just leery of those type of caps. Keeping an eye on them would be good. If they do leak, be careful. If you are using a Weller soldering station, the goo eats the tips up in less than a day.

Meanwhile, I pulled all the tubes for testing. Unfortunately, careful as I was, the cap broke off the 6JS6 and let the air in :tears:

The tube looked well used and may have been weak, but now I'll never know for sure. I have 1,000s of tubes NOS and pulls but had a heck of a time finding a replacement.

As for the others, I check them with a TC-162 and found many had shorts or excessive grid leakage. Luckily, I had replacements for all on hand.
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While searching I came across this Servicemaster 3AT2 made in Korea. I think it's the first Korean tube I've come across. Don't plan on using it, just though it was interesting.
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Back to the 6JS6 saga. I finally dug up a used one that tested good and popped it in.

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Hmm. Nothing on the screen. Let it run a while and slowly the screen lit up dimly with a weird image.
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A while later, it got a little better.
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I hooked up by Seco meter and found it was drawing less than 100mA. Schematic calls for 225. Time to search for another 6JS6....
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Just as I was about to give up, I found one mixed in with my octal tubes :)

It certainly draws more current, but no HV at first then it suddenly sprang to life and I got a nice, bright image back. At least until I turned it off and back on. No HV, drawing 200mA and starting to red plate!
https://c1.staticflickr.com/5/4243/3...71822a79_c.jpg

I popped it back in the tester and found it has a short. I was able to tap the side a few times and clear it out.
Put it back in the set and it has been been working without trouble for a couple hours.

Even so I'm not crazy about leaving it in the set so took a chance and bought a NOS tube on ebay for $14. I got lucky and it works great!

The image now fills the screen, vertical linearity is pretty good and no more streaking.

I do still need to cleanout the HV cage and fabricate a shield for the HV shunt regulator. Eventually, I'll pull the chassis and go over it too.

Even though it's working pretty well, it's got issues. Like I sporadically loose vertical sync, and focus control is at one extreme, occasional arcing and dirty controls.
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One last thing for now, I stumbled across a NOS channel knob on eBay.
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After a bit of a struggle, I got the old knob off. The clear plastic fine tuning was filthy and got a good cleaning.

Here's how I've got the bulb sitting in it's holder. I'm not sure I've got it positioned quite right.
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Here's what I got after fighting with it a while. I really need to setup a mirror so I can see what's going on while I position the bulb.

Even so, it's definitely better than before.
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One of my favorite Zenith channel knobs!!

Nice. You do good work on your set's.

I occasionally lose vertical sync for a couple seconds. Also, the vertical looks like it is about to collapse then clears up. I have never replaced the vertical integrators so maybe that is the problem. The focus control on mine is at the end of its range even after replacing the string of focus resistors. I wonder if this was the case when new. I restored mine ten years ago and I am quite sure I need some new tubes here and there judging by the overall performance is not as perfect as it was before. I need to look on Ebay for spare parts. I would like to have a new convergence cloverleaf as I had to glue mine back together when I first got the set.

Replacing the tubes definitely helped. There is a HV adjustment control. It could be we need to tweak that and our focus would be good mid range on the control.

Has any more progress been made on this set? I'm interested to see how it turned out.

No, sorry I haven't had time for any projects the past few months. I've been too busy with work and fixing up my house.