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  #16  
Old 09-14-2017, 09:38 PM
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Quote:
Originally Posted by walterbeers View Post
Also another thing that i have seen happen is that the HV cup itself develops a crack or a spot in which the HV will arc through to the chassis. In this case you just need to replace the HV cup.
If it is a single point leak you can often fix the cup by, cleaning the snot out of the cup, drilling out the carbon path and filling the hole with RTV silicone (which has a higher dielectric strength than the plastic used in most cups ). It ain't what techs did back in the day, but with some cups NLA it is sometimes the best approach.

Also some sets (IIRC Zenith mostly) used resistance wire for the HV rect heater winding which must be accounted for when replacing.
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  #17  
Old 09-15-2017, 12:01 PM
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PM received, D09 schematic and Stan Prentiss list of production changes has been emailed. If yours is a code 2, check if the HV regulator cathode circuit changes have occurred. A regulator limiter diode and 10 meg is added on the other side of the 1K 5%

Good luck with cup repairs, I put a piece of #1/0 HV cable jacket insulation flattened out under the HV cup of a 16" color Zenith (chassis 12A10C15) that had burned a hole thru arcing. It is still holding up after 20 years, my woodshop set.

I drilled out the conductive carbon path first. Not sure if I used RTV but that is a great idea. The black stuff I suppose the same as used on tripler-fly terminals.

The cup to chassis mounting screws were long enough and there was clearance for the tube to be installed
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Last edited by DavGoodlin; 09-15-2017 at 12:22 PM.
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  #18  
Old 09-15-2017, 04:45 PM
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Quote:
Originally Posted by Findm-Keepm View Post
I'd also clean the regulator socket and cap above the cage - it has full 25KV on it and looks as though it may be just as dirty, judging by the plate cap.

HV loves and attracts dirt - it's a much lower resistance/impedance and may be your only problem.

Will do...thanks!
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  #19  
Old 09-16-2017, 10:52 AM
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Hi--

I tried most of the above options....I cannot pull the horizontal output tube (is it above the 3CU3?). It has some sort of a round metal ring that locks it into place....I feel like I would break it if I tried any harder....but I did clean its cap. The 3CU3 glowed orange and/or blue....the back of the crt had some blue lighting up and the sounds of a CRT coming up, but nothing in the screen (pic does not show the blue).
I see a crack on the CRT as well. (see pic). I did not notice that before. I pulled out the cap a bit to investigate, but plugged it back in.
Sound was fine, no smoke or arcs.
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  #20  
Old 09-16-2017, 01:47 PM
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The tube above the HV rect is the HV regulator....You remove it by pushing that ring down before/while pulling the tube.

If you have HV, blue neck glow, no picture, and a crack in the CRT glass, then your CRT has probably lost vacuum through the crack and is now ruined....Good luck in the CRT hunt.
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  #21  
Old 09-16-2017, 04:41 PM
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Yeesh, never saw a CRT go like *that* before. Oh well, at least it was one with the beginnings of a cataract.

Keep your eyes open for a Zenith Chromacolor II with a 23V CRT, no cataract issues and it should be a drop-in swap. There may be minor mounting hardware issues but that's it. They're relatively common and there are probably a lot of NOS units in hiding considering the 4-lead safety cap fiasco.
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  #22  
Old 09-17-2017, 10:38 AM
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Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.
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  #23  
Old 09-17-2017, 12:49 PM
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Quote:
Originally Posted by Radiophile2001 View Post
Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.
Possibly a poor connection between the HV button and the internal coating of the CRT caused arcing and localized heating around the button, which cracked the glass.

jr
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  #24  
Old 09-17-2017, 01:59 PM
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Or someone tried to "pry" out the HV Anode connector. In a hurry, I did it once to a 23EGP22 set. 13 days of worry while the customer mulled over dad's $61 estimate for repair (filter cap, a rectifier and an HV cup...), I'd have eaten a picture tube. In the end, she bought a set at Sears. I got to junk the Motorola, and breathed again.

The crack didn't curve - it was straight as an arrow, to the side I had pried from...
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  #25  
Old 09-17-2017, 11:05 PM
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Quote:
Originally Posted by Radiophile2001 View Post
Yeah, as I said....ghosts in the machine!....How would a CRT crack like that without some kind of impact?
Anyway, sounds like this one is toast, as far as my skill set goes....!
It was worth a try tho and thanks, all, for the advice on this old Sylvania.
I wouldn't trash it, good 23V CRTs are easier to find than Sylvania tube tabletop sets. Swapping out CRTs is fairly easy, it's the setup adjustments that are tricky.
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  #26  
Old 09-18-2017, 08:12 AM
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Cool, thanks....I will not trash it.....although I do not know where to find one....
That set was closed up tight....the room is locked, I don't know how anyone would have touched that anode connector....bizarre...!
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  #27  
Old 09-18-2017, 08:36 AM
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Any delta-gun color CRT the same screen size form 1965 to the last ones made ~1980 should be compatible. Tubes made prior to 1968 will mark a 23" view-able area tube 25 (ie 25AP22) tubes made after '68 will mark them 23V (ie 23VAXP22). Look for delta gun color CRTs or TVs that contain them for sale.
Bob G has some 25EGP22 CRTs that might work http://antiquetvguy.com/FramesetPage...FrameSet1.html
The ETF also has a large selection of CRTs that may work in your set. http://www.earlytelevision.org/crts_for_sale_color.html

Or look for a early to late 70's solid state set with a deltagun CRT the same size like an RCA XL-100, Zenith CCII etc.
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  #28  
Old 09-18-2017, 10:12 AM
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Thanks!
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  #29  
Old 09-18-2017, 01:08 PM
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I have had three quality CRTs ruined by gremlins over the years.

The first two : Zenith 1967 color 25GP22 arced and sheared neck off at CRT bell, under the yoke. RCA 1965 color CTC16X had rebuilt channel master 21FJP22 and worked great, one day I turned on and heard crackles. Necked the same way, with weight of yoke/converge yoke landing on chroma board.

The last was a few years ago, a 1965 metal Zenith 24MC32 with a 21FB RCA HiLite, the neck sheared right at the blue lateral magnet, testing like new just weeks before. I was so upset, I gave the set to another VK member, who had a NIB crt for it.

lesson learned: NEVER spin anything metal on the CRT neck, like the blue lateral magnet/spring. acting just like a glass cutter, this may have been done before I got it when it was set up.
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  #30  
Old Yesterday, 05:51 PM
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I have seen hi voltage problems crack the bell, And blow the neck off CRT. Make sure you find and repair the hi voltage problem before you turn the set back on with a new CRT. If this set has pc boards, Re solder the board connections and tube socket pins.
You have a really cool set. And they do produce a good color picture.
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