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 Post subject: Need help with 2 Admiral TVs 19A11 and 26X76
PostPosted: Aug Sat 13, 2022 12:31 am 
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Joined: Jul Wed 09, 2008 12:40 am
Posts: 497
Location: Orlando, Florida 32803
The first is a 19A11 "Chinese" with the 17T1 chassis. It started misbehaving a little while ago. It now has a double picture on the screen and the focus just isn't there. Audio is good. Totally recapped by PO.

The second is a a 26x76, chassis 24D1. Replaced the multi section cans. The PO had gone though and done all the wax paper caps a few years back. Can just barely tell that video signal is getting through but its nothing watchable, audio isn't coming through either.

I'll try and get some photos tomorrow.


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 Post subject: Re: Need help with 2 Admiral TVs 19A11 and 26X76
PostPosted: Aug Sat 13, 2022 1:46 am 
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Joined: Apr Sat 06, 2013 1:18 pm
Posts: 789
Location: New Hampshire
One at a time. Double pix if a hoz osc problem will be side by
side pixs. If top & bottom its the vert. Start painlessly with trying
tubes first, You can rob peter to pay Paul. Try the tubes from the other
set if the same.
On the other set IIRC Admiral used a separate audio chain. If so
look at the tuner tubes first.

73 Zeno 8)
LFOD !


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 Post subject: Re: Need help with 2 Admiral TVs 19A11 and 26X76
PostPosted: Aug Mon 15, 2022 11:33 pm 
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Joined: Jul Wed 09, 2008 12:40 am
Posts: 497
Location: Orlando, Florida 32803
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 Post subject: Re: Need help with 2 Admiral TVs 19A11 and 26X76
PostPosted: Aug Tue 16, 2022 2:01 am 
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Joined: May Mon 24, 2021 2:33 pm
Posts: 107
Location: Chapel Hill NC
Location: Chapel Hill, NC
It looks like two unrelated issues -- horizontal oscillator and focus voltage. That set has a separate horizontal oscillator from the high voltage generation, and the entire horizontal deflection circuit is contained in half of a 6SN7. Howard Holden has written a wonderful analysis of this clever circuit, and he's commented on it here many times. https://earlytelevision.org/pdf/admiral_tv.pdf Does the picture change if you adjust the Horiz Hold? If you're living right, perhaps just changing that 6SN7 will fix the double picture. But I suspect it's a cap or resistor that has decided to change value, despite having been replaced earlier.

The focus voltage (did you try adjusting the focus control?) is created by a voltage divider from the 5KV HV, made up of a long string of high-value resistors. They change value over time too, so give each one a check. Also, watch for any signs of arcing or dirt tracks between and among the HV wiring points.

Here's the Wallace's TeleAids chapter on the Admiral 17T1 chassis (usually the model 19A11 uses the 19A1 chassis). https://earlytelevision.org/pdf/admiral_17t1_telaides.pdf Sam's and Rider's for the 19A11 are at the same location on the ETF website.

_________________
Mark Nelson
http://tv-boxes.com
TV columnist for AWA Journal


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