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 Post subject: RCA T-100 TV nada high voltage???
PostPosted: Jan Sat 27, 2018 11:00 pm 
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Joined: Apr Wed 03, 2013 2:38 pm
Posts: 31
I recently picked up a rca t-100 B&W tv with the original stand, restoring old radios, I'm getting better but old TV's
I'm just getting started. So I went through and replace all Electrolytics and paper caps. Tubes that were bad were
replaced. Picture tube checks good. When I thought everything was a go, I slowly brought the voltage up, found there is no high voltage.
Pwr transformer seems to be good altho have not been able to locate Sams. Any ideas before finally securing schematic.


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Sat 27, 2018 11:33 pm 
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Location: Durham, NC
I think that's a KCS-38 chassis, from 1949-50. There's a service manual for that on the ETF site: http://earlytelevision.org/pdf/rca-9T256-manual.pdf

When you say "high voltage" do you mean the usual 100-200 volts on the plates of most of the tubes, or the CRT's anode voltage (9KV)? This set uses a field coil on the speaker for the power supply filter choke, so the speaker needs to be plugged in, and field coil working.

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Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
tv-boxes.com


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Sat 27, 2018 11:36 pm 
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Location: Redlands CA
Most often lack of HV is due to an inoperative Horizontal Oscillator. Is the Plate of the 6BG6 glowing red after a minute? (Don't run it like that if it is).

Do you get any sound or at least static in the speaker?


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Sun 28, 2018 1:15 am 
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Joined: Apr Wed 03, 2013 2:38 pm
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By golly "You can teach an old dog a new trick" I'll plug in the speaker and see what happens. Stay tuned......
btw the 6BG6 does not get red so good to go on that one


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Sun 28, 2018 1:19 am 
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Location: Woodinville, WA USA
This doesn't address your HV question directly, but here's a T-100 article with some restoration notes that may be interesting:

https://www.antiqueradio.org/RCAT-100Television.htm

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Mon 29, 2018 8:11 pm 
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Joined: Apr Wed 03, 2013 2:38 pm
Posts: 31
I plugged the speaker in and was hoping for a miracle but it didn't happen. I double checked the 6BG6 tube, it checks good. All filaments are burning but there is no activity including sound. I DL the manual so I guess it's start digging time. If anybody has any ideas(to send me in the right direction) please do, as I said I'm new into tv repair as I would really like to get this going hooked up with a dvd


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Mon 29, 2018 8:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Lafayette, CO
My suggestion is to get the power supply straightened out first. Those chassis mount power resistors really need to be looked at. Several salvage ones l threw away after they were pried open--these were all from sets like yours. I will let others chime in on capacitor upgrades. If you can turn up a test picture tube somewhere, that will save some guesswork later on. Craig


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Tue 30, 2018 8:22 am 
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Greetings to stratozen and the Forum:

In the good old days when I was in TV servicing, an NE-2 neon lamp was very handy. Just bring it near the 6BG6 and it should light strongly if the horizontal sweep circuit is working.

If the horizontal sweep circuit appears to be working, then there is not much else left to go wrong... perhaps the 1B3 or any doorknob capacitors after it or the CRT itself.

If the NE-2 is dimly lit or not at all, check for proper screen voltage on the 6BG6 and make sure the B+ supply is at the correct voltage. Do not attempt to measure the 6BG6 anode (plate cap).

If these voltages are OK, then it is scope time. Look for incorrect or insufficient horizontal drive signal to the 6BG6 grid.

It is possible to have either a bad flyback or a bad yoke. Look for less troublesome things first.

Regards,

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Jim T.
KB6GM


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Tue 30, 2018 8:30 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 250
Hey! Check the B+ first! There's no sound....


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 Post subject: Re: RCA T-100 TV nada high voltage???
PostPosted: Jan Tue 30, 2018 11:37 pm 
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Location: Durham, NC
Yes, the power supply operation is the first thing to check. The service info has voltages for all the tube pins. Start with those two 5U4s and work your way through. Anyplace there's no or very low voltage, you can stop and figure out what's wrong there.

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Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
tv-boxes.com


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