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Old 10-07-2017, 03:44 PM
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Freon Freon is offline
Apprentice Necromancer
 
Join Date: Jul 2017
Location: Normal, IL
Posts: 23
Help wanted resurrecting 1969 Zenith 12A10C15

Long story short, this Thursday I rescued a 1969 Zenith A3520, chassis 12A10C15, from my college town's electronics recycling drop-off point. A knob-tuned Zenith color set was my Holy Grail of CRTs and my long search for one was finally over. I assumed it was a mid-70s set, probably solid-state.

I got it home, realized what I had was a genuine tube set, what appears to be an early Chromacolor, right when they started using plastic cabinets. I had class soon so in the nick of time I foolishly did a test power-up. Things actually looked pretty promising, I saw the orange glow of tubes, and in 20 seconds the CRT began to light up white and was suddenly halted by a loud screeching noise of varying pitch, which turned out to be arcing somewhere on or below the bottom middle of the CRT body. Some split-second sputters of snow-like lines blinked on the screen as the screeching continued. After 25 seconds with no signs of improvement I figured enough was enough and I didn't want to cause more damage than I potentially already have. I shut off the power, the screen blinked out like it's supposed to. And no, I'll NEVER do something that stupid ever again. I'm very sorry.

I decided this set would be better off going to a tube TV enthusiast with more experience and equipment so I listed it on the classifieds of this forum. I knew about this place from some months of lurking and had made an account prior. I actually got enough encouragement from other members that I decided to change my stance. I'm definitely going to need your help here. I'm learning everything here as I go, and I'm slowly starting to get aquainted to tube equipment. Videos from Shango066 and Mr. Carlson's Lab on YouTube, in addition to reading through repair threads on this very forum, have been a big help.

Yesterday, I figured out how to get the set apart and gave everything a much needed dusting on the inside. Here is a photo album with more info, remarks, including where I believe I saw the arcing.

What I can tell by now is that the CRT is probably okay, and so is the horizontal and vertical deflection as I saw a picture fill the entire screen. I still haven't nailed down the cause of the arcing; that is my primary goal.

Someone on the classifieds thread mentioned that the focus voltage divider may be arcing. I have no idea where that is.

Last edited by Freon; 10-07-2017 at 06:50 PM.
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