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 Post subject: 1938 RCA Model 96K6 repair
PostPosted: Nov Wed 13, 2019 5:29 am 
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Joined: Mar Thu 28, 2019 2:03 am
Posts: 2
Location: Olney, MD
A friend of mine asked me to take a look at a 1938 RCA Model 96K6 radio that was gathering dust in her parents house and see if I could get it working. I'm in the middle of replacing the caps and the brittle and worn wiring. Other than that the radio appears to be in fine shape, but I won't know until I finish recapping, replace the tubes and power it up with my variac. I've never worked on a floating ground chassis and am considering replacing the two prong power cord with a three prong one and grounding the chassis. Is this a recommended practice?


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 Post subject: Re: 1938 RCA Model 96K6 repair
PostPosted: Nov Wed 13, 2019 12:51 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2077
Location: Lafayette, CO
As that is a transformer-powered set, just replace with a two- prong cord. You'll find a cap that is a signal ground attached near the switch, that's much the same thing as a 3-prong cord. Others will chime in about a safety cap. Nice radio, by the way. Do mention your location, acquiring minds want to know. Craig


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 Post subject: Re: 1938 RCA Model 96K6 repair
PostPosted: Nov Wed 13, 2019 1:14 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
Posts: 28408
Location: Annapolis, MD
I'm not sure what is meant by "floating ground chassis". B- and chassis are the same thing in this set.

There's no harm in adding a 3-wire cord, but it could make the set noisier. There is a ground connection next to the antenna terminal. The best performance come from grounding this to a ground that does NOT come through the building AC wiring, In the old days, this was typically a cold water pipe.

If you add line filtering capacitors, be sure they are "safety" types. Read all about it here:
https://www.justradios.com/safetytips.html

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"Even if you don't understand Ohm's Law, you are still required to obey it."


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 Post subject: Re: 1938 RCA Model 96K6 repair
PostPosted: Nov Sun 17, 2019 9:40 pm 
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Joined: Mar Thu 28, 2019 2:03 am
Posts: 2
Location: Olney, MD
Thanks for the advice. I definitely do not want to introduce more noise into the circuit and didn't realize the cap off the switch was a signal ground. I should have. I am also using safety caps and installing a fuse. Thanks again for the good advice, and I'll post as I make more progress (and continue to learn) on this project.
Bob - Olney, Maryland


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 Post subject: Re: 1938 RCA Model 96K6 repair
PostPosted: Nov Wed 20, 2019 4:41 am 
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Joined: Dec Sat 24, 2011 9:17 pm
Posts: 6221
Location: Vancouver Island, Canada
Right, in general, AM and FM receivers work just fine with a 2-prong cord.
Always have the knobs on the radio when it's in use.
Modern electronics use switching power supplies on almost everything, which transmit noise at radio frequencies. So if your have a lot of noise on AM, unplug digital devices.
House wiring can act as an antenna for external noise, such as street lights.

Also the hole in the chassis is usually too small for a 3-strand power cord, so you have to enlarge the hole and create a new strain relief all for not much benefit.

You can install a polarized cord and orient it so the hot side, narrow prong, goes to the Off switch.

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 Post subject: Re: 1938 RCA Model 96K6 repair
PostPosted: Nov Wed 20, 2019 6:01 am 
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Location: Mission Viejo, southern California
I've found that most radios with power transformers receive better with a three wire cord to provide ground than without it. It is also good for safety.

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