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 Post subject: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 7:16 am 
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Joined: Dec Sat 21, 2013 5:15 am
Posts: 427
Location: Puyallup, WA 98371
I bought one of these in about 1972 for $5 at a garage sale. Used it several years, but by 1980 or so the picture had become very dim, but it otherwise worked well. I sent the CRT to a rebuilder in Spokane. Got it back and installed it. Turned the set on and the power transformer promptly burned out. It it were today, of course, I would have recapped it. But it was 30 years newer then, and I didn't. I still have it (hasn't been plugged in since that happened) and am thinking about repairing it. I have a very similar 1950 model that worked well when last turned on (also about 30 years ago) that has the AM FM tuner, but it's in a homemade plywood case covered in wood-grain contact paper, so it's a parts set. The 20X11 has the rectifier tube socket in the top of the transformer case. If it's a suitable transformer replacement, I could come up with a new mount for the tube socket, or maybe even swap the tops of the cases and wire it in as it was originally, if that's possible. I'll need to dig that set out and check the model number, then get a schematic.

Just wondering if the shock of a freshly rebuilt CRT would likely have caused the failure, or could the rebuild have been faulty? I don't have a picture tube tester, but I could get one if that seems as likely a cause as old capacitors. Any thoughts? Any proper replacement transformers available out there?

Thanks,

Dale

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 1:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1947
Location: Lafayette, CO
There are more than a few sets out there that would LOVE to be 'surprised' by a newly rebuilt picture tube. We need to find out what that transformer is 'seeing' before we go any farther. How does it act without the rectifier? Do the tube heaters light up? Sounds like the entire set could use a re-cap. Craig


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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 4:16 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 1792
Location: Dallas, TX
It is very unlikely that the CRT rebuild was the cause of the transformer burn out. Just about the only thing that would come close to causing damage would be a short. You can check that with an ohmmeter at the CRT pins. The schematic should show the tube elements to tube pin connections.
More likely would be that a filter cap or the rectifier chose that time to fail. Could also be a wire or similar that shorted because of the chassis movement because of the CRT switch out.

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 4:27 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 27938
Location: Detroit, MI USA
If the transformer does prove to be bad, there have been enough Admirals parted out over the years that you should have no trouble finding the correct power transformer.

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 5:46 pm 
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Joined: Mar Sun 01, 2009 10:27 pm
Posts: 5020
Location: Ann Arbor, MI
If the filter caps decided to go bad while you were waiting to get the CRT back then I would expect that there would have been arcing and fireworks inside the 5U4 as it melted down. Of course you would have had to be looking in the general direction of the 5U4 to see that.
Power transformers can overheat and smell due to a short and not be destroyed. Try removing the 5U4 and unplugging the CRT and then try powering up the set again. If the transformer stays cool, it probably is usable.

A shorted heater in the rebuilt CRT seems unlikely. But measure the resistance of the heater and compare it with another CRT to find out.

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 7:39 pm 
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Joined: Dec Sat 21, 2013 5:15 am
Posts: 427
Location: Puyallup, WA 98371
Thanks all. I'm not going to be able to look at this this weekend, but it sounds like it's unlikely to be the CRT. That was the one change at the time the power transformer went out, so I wanted to rule it out as much as possible. The transformer smoked and dripped - it would have caught fire had I not been there to promptly unplug it. I'm not going to remove the rectifier tube and try plugging it in again.

I'll post on the classifieds for a replacement and replace all the caps, check the resistors, and try again. This is one of those things that has bugged me for years, you know? I guess being tired after a week's work made me finally ask about the chances of the CRT rebuild possibly being to blame.

I'll let you know how things go after I do a full electrical restoration. Having a rebuilt CRT in a set I'm pretty fond of that's otherwise fried is something I'd like to resolve :)

Thanks again,
Dale


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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sat 18, 2019 9:29 pm 
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Joined: May Sun 07, 2017 11:35 am
Posts: 584
Location: Belrose, NSW, Australia
It does sound like your transformer's a goner but it's easy to unplug everything from it and do a check with a dim bulb tester (google it)

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Wed 22, 2019 7:28 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2341
Location: Seattle, WA, USA
You should be able to find a new transformer for that set. Those sets are pretty collectable and the cabinets usually get smashed so I suspect that if you post in the classifieds here and / or on the ETF website you will be able to find a new transformer without too much trouble.

-Matthew

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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Sun 26, 2019 3:51 am 
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Joined: Dec Sat 21, 2013 5:15 am
Posts: 427
Location: Puyallup, WA 98371
7jp4-guy wrote:
You should be able to find a new transformer for that set. Those sets are pretty collectable and the cabinets usually get smashed so I suspect that if you post in the classifieds here and / or on the ETF website you will be able to find a new transformer without too much trouble.

-Matthew


Thanks, Matthew. I'm not going to get to this until winter, but I've posted the WTB ad today.

Thanks again,
Dale


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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Mon 27, 2019 9:35 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 731
Location: Rockaway , nj 07866
This is the power transformer that are usually painted black or the transformer that is hooked to the 1b3 or 1x2 , that's the flyback transformer


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 Post subject: Re: Admiral 20X11 Repair
PostPosted: May Thu 30, 2019 7:21 am 
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Joined: Dec Sat 21, 2013 5:15 am
Posts: 427
Location: Puyallup, WA 98371
Kramden66 wrote:
This is the power transformer that are usually painted black or the transformer that is hooked to the 1b3 or 1x2 , that's the flyback transformer


It's the main power transformer, not the flyback transformer.

Dale

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