On going Zenith 25MC33 roundy restoration

[Electronic M]

Great Dave! PM sent.

I was able to achieve decent purity(on any other set the more OCD parts of my mind would compel me to make it just a bit better) by flipping the rings 180 degrees and degaussing it even more rigorously than before. It was the first time I've been nuts enough to stuff my degauss coil inside a set let alone while the set was running.
The vertical out cathode cap tests like new on my Heathkit C-3 so I'm starting to test resistors.

[dieseljeep]

[QUOTE=Electronic M;3071062]I seem to recall someone saying that 70's "loss leader" roundys did not usually have safety glass installed when they were built so I'd imagine if it was okay then it should be okay now. I've never had a roundy CRT implode (knock on wood) and I've got 4 sets and 6 total CRTs, all of which I've handled at some point. The one I cataracted above even got tapped with a hammer on the screen a few times and is fine so I'm not all that worried.
QUOTE]
That someone was wrong!
Any set without either a safety glass or some kind of an integral implosion protection would never pass U/L listing standards.
All the low end roundys at the time used either a 21FJP22 or a 21FBP22 with a tempered safety glass and a rubber sealing ring.
If you notice, the bonded safety glass is not tempered.

[Electronic M]

So is this a big enough issue that I should transplant the safety glass from my decated Zenith spare or swap that CRT in?

[dieseljeep]

Originally Posted by Electronic M

So is this a big enough issue that I should transplant the safety glass from my decated Zenith spare or swap that CRT in?

Keep your Zenith, all Zenith.

[Electronic M]

I'll have to test both tubes to see which is stronger, as IIRC there was a reason that Zenith jug didn't end up in my CTC-4... If it is weaker and or has worse color tracking than the Silver-Glo I'll probably just swap the safety glass.

[Tubejunke]

Hey Tom, great job on that set. I have one that is identical, but with a metal cabinet. I have posted a thread or two about this, but being on the same subject, I thought that you might know something that I need to verify and perhaps correct in my set.

Did you feel or touch the horizontal efficiency (linearity) coil while tooling around under that chassis? Mine is wobbly and supposedly these have a habit of getting brittle and cracking. Just wondering what you found. Do you happen to have an extra by chance? Most people in the know say it needs replacing if it has cracked.

[Electronic M]

My lin. coil does not seem brittle, but it looks a bit melted. The shaft to the chassis looks almost like it broke long ago and was melted together sloppily with a lighter. It is hard to describe, but I could post a picture if you want. I wonder if the slug is stuck...

I have a spare form that is currently wound with the wire to be used as the horizontal hold coil that I would offer you if there weren't potentially two sets in my collection that might need to have their wire wound on that form.

[Tubejunke]

Originally Posted by Electronic M

My lin. coil does not seem brittle, but it looks a bit melted. The shaft to the chassis looks almost like it broke long ago and was melted together sloppily with a lighter. It is hard to describe, but I could post a picture if you want.

Originally Posted by Electronic M

My lin. coil does not seem brittle, but it looks a bit melted. The shaft to the chassis looks almost like it broke long ago and was melted together sloppily with a lighter. It is hard to describe, but I could post a picture if you want. I wonder if the slug is stuck...

You can post a picture if it's not too much trouble. I found a source for a replacement, so I guess I may as well just replace it since the horizontal and HV sections are so critical in color sets. Most of my collection has always been 40s-50s black and white, so I am a bit lost at times with the many issues that come into play with color sets. I must say that mine came in the door with one beautiful color picture after decades of dormancy. Like yours, I had to replace a few tubes in the HV section and the plate of my H.O. tube was glowing red. Once I replaced the bad tubes it came alive like the day it came off of the assembly line. Of course after about an hour some quirks developed and the color went out. Someone here sent me a crystal that supposedly is a likely culprit with the color problem, but who knows really. Nice of them to help me though. That was over a year ago and I haven't had time to do anything else, but I'm getting the itch bad. I need a nice control door if you see one or have one. Mine is there but has a few dents albeit small.

[Electronic M]

Tubejunkie: Glad you found a new lin coil. I'll post a picture when I pull the chassis later today. The door on my set is dented too, on the handle. I may try to fix the dents, if I don't like the result I do have a spare door. If whatever door I have left at the end is presentable I'll let you know about it.

Originally Posted by dieseljeep

Keep your Zenith, all Zenith.

That is how it will be. The Zenith tube tests 85% on the red and 76% on all else and the Silver-Glo tests 72% across the board.
The Zenith tube is on the border line of failing the color tracking test though. So if I can't get the colors to track I may have to do a mild rejuv to balance emissions better.

I'm starting to think the ETF CRT tester is tuned to be a bit optimistic in it's readings. It tested the Silver-Glo as ".1 Excellent" which as the set was advertised for the meet is the point where the meter pegs on their tester...On my tester it tests at 72% of full scale which is the lower end of 'good'. I've tested CRTs which make that value look anemic on my tester.

[dieseljeep]

Regarding the slogan about keeping your set all Zenith.
I was just quoting an old advertisement about keeping your GM car all GM, by using only their replacement parts.

[Electronic M]

As promised here are the pictures of the lin coil on my set.




I subbed in my spare Zenith 21FJP22A today.



About 2 years ago this tube was the first tube of any type which I successfully removed the cataract on. I decided to do the swap the lazy way...Pull the chassis, neck hardware, and degauss frame(I put the set face down for this part) then loosen the adjustable tension band and lift the old CRT out. I then dropped the new CRT in, loosened the screws which connect the CRT mount hardware to the mask, tightened the band snug, tightened the screws back up then tightened the band a pinch more.




All that is left is to set up the neck hardware for the new tube before I can work on the electronics again.

[Electronic M]

Originally Posted by dieseljeep

Regarding the slogan about keeping your set all Zenith.
I was just quoting an old advertisement about keeping your GM car all GM, by using only their replacement parts.

I'm 21 years old and suspect that slogan was before my time as I've never heard it. Though it has been a long time since my folks bought GM...The last Non-Honda made car in my family was an 89' Chevy Baretta which was an epic POS from the moment it was built.

Too late to go back on the decision to change the CRT now....Though I guess if there arose some compelling reason to do so I technically could, but I am too LAZY to just do it for no reason. I was considering putting the Zenith CRT in for originality and to improve purity days ago anyway....Plus it is safer now in the event of random implosion.

[Electronic M]

Originally Posted by Electronic M

...Though I guess if there arose some compelling reason to do so...

Guess what!....

I powered up the set, waited patiently for a raster and, after far too long, went behind the set to see what the deal was.
I was greeted with this....









It would seem the Zenith tube is gassy...So much so that it was loading down the HV to less than 1/5 of what it should be...I tried to get better photos of it, but some LOUD ominous popping noises had me scrambling for the power switch....

I'm very pissed that I went to the effort of installing a POS in my set and that it was not obvious when I tested the tube earlier. It is almost as bad as when I tested the 21AXP in my CTC-4 and found it in the same state. I guess this means I no longer have a spare roundy CRT(or should I say I never had one from the start?).

I guess I should count my blessings that I never bought a roundy with a dead tube thinking I could drop this in. It also tells me what will happen if I get stupid enough to put the 21AXP back in to my CTC-4....

I already ripped the turkey back out and cut the safety glass I siliconed to it(years ago) off...Should I go to the effort to caulk the safety glass from the dud Zenith CRT onto the Silver-Glo?

UGH, what a lousy day!

[mstaton]

Well that really sucks! I recently went to go look at an Admiral roundie combo. I tested the tube and it was weak. I did a light cleaning of the guns and it came up well into the good range. So I decided to fire up the set. It came on with HV and had a raster but was arcing inside the neck and had the purple glow. Sometimes CRT testers don't show everything.

[dieseljeep]

Ouch!
I hope you didn't get that CRT from anyone I know. The tube looks vaguely familier. I either traded it or gave it away. They wanted it as a dud.
I couldn't get a decent picture on it to save my soul. The one I had didn't have a cataract on it, for being that old.