#1
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Questions regarding broken CRT lead
Hello,
I have been working on an RCA CTC-20C which started with a mostly dead CRT (among other issues). After some time on the rejuvenator, the CRT was able to produce a fairly good picture overall. This became short lived when I decided to work on the chassis some and afterwards would not get any neck glow. Upon de-soldering the bakelite base, I noticed that one of the leads had broken off mostly flush (somewhat recessed) to the glass. Has anyone encountered this type of issue before? If so, has anyone found a way to repair this type of damage? Thanks, Matthew |
#2
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If it is recessed things get difficult.
I'm guessing you lost a heater lead. If it was not a heater lead you could probably use conductive glue, but the heater draws a lot of current and odds are conductive glue won't survive that... If the glass is reasonably thick around the lead and there's a raised bit of glass wrapped around the lead stub then you may be able to expose a solder able nub by grinding the glass down with a small gentle dremmel grinding bit.... but grind too far and you loose vacuum. Also you have to apply heat with the soldering iron for the shortest possible time needed to get a solder joint....too long heating it and the glass will crack and the vacuum will leak... grinding the glass will also make it more prone to cracking....... What you have is a game of finesse, speed, judgement and luck with the future of your CRT on the line....No pressure.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#3
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What a heartbreaking experience. I will try to clean up the area and see if I can expose any of the wire. It appears that there is a bit of oxidation at the base of all the leads.. But only the one managed to break (or maybe burned up; the glass stub you speak of that can be ground down is chipped.)
Going into the project, I initially never had much hope with the initial condition of the CRT. But things were really looking positive after the rejuvenation. It was a joy to watch for the brief time I could. |
#4
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Quote:
Further, if you rejuvenated the tube with a CRT tester, bear in mind that any improvement you may notice won't last long, so it is probably just as well that you will have to replace the tube. Rejuvenation is usually done only to restore a CRT to usable condition (albeit dim) until the tube can be replaced; it is not meant to be a permanent fix. The tube will eventually dim again, at which point it must be replaced. CRT brighteners were often used in the 1950s-'60s to extend the usable life of dimming tubes, but again, this was only a stopgap measure and usually resulted in a dim CRT again within months; the only solution in this case was either to replace the tube or the TV.
__________________
Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. Last edited by Jeffhs; 12-20-2018 at 07:13 PM. |
#5
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See reply #218.
http://www.videokarma.org/showthread...master&page=15 |
Audiokarma |
#6
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This tube is a round 21fjp22. The TV had a brightener on it when I had acquired it, but would not produce much of any kind of image initially. On the tester none of the guns would show any readings until the rejuvenation was performed. The difference afterwards resulted in a picture that was very impressive in a lit room (compared to an extremely dark unfocused looking picture in a dark room). I suppose I had hoped maybe this would be a fairly long term fix.
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#7
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If it is not the heater conductive glue will work fine.
If you are afraid of overheating to solder, get some pure Indium wire off ebay and use that as solder, using ordinary liquid flux. It melts at just the right temperature, solders easy and won't melt with ordinary base heat. Indium can't hurt ... its a good solder and sticks well to copper, steel, other tube pin alloys, and ordinary solder. I've even had good luck soldering to germanium with it! Use a small wire and glue down to the glass after soldering. But ... I've had good luck with regular solder and a tiny tip on both CRTs and a very rare iconoscope. |
#8
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Quote:
Rejuvination is risky use all safer measures first.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#9
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Agree 110%. Rejuv only after all other measures (including CRT brightener) have failed. Learn't that the hard way many moons ago. |
#10
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...
Last edited by andy; 11-18-2021 at 04:49 PM. |
Audiokarma |
#11
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I have used silver-filled (i.e., conductive) epoxy to repair a similar problem on a CRT base:
https://antiqueradio.org/CapehartFar...airingTubeBase Phil Nelson Phil's Old Radios https://antiqueradio.org/index.html |
#12
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But is silver epoxy conductive enough to repair a lead that carries heater current in a 3 gun color CRT (1.8 amps nominal, and much more at cold turn on) ?
jr |
#13
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Don’t know offhand, but this page has some specs:
https://www.mgchemicals.com/products...ive-epoxy-8331 Phil Nelson |
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