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 Post subject: RCA 8x541
PostPosted: Dec Sun 03, 2017 7:55 pm 
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Joined: Nov Wed 22, 2017 6:01 pm
Posts: 10
Hi: I am a newbie to this hobby, and have been working on an RCA 8x541. I have replaced most of the caps and test run it on a Variac. Before recapping, it had a loud hum, which is now gone. Unfortunately, all I hear now is a very low hum, with occasional lightning storm type static.

After reading on this forum, it seems that in addition to whatever other problem it has, it may have the dreaded SMD. If this is the case, do I even want to continue to try and repair it?

I don't want to sink a lot of time and money into it if the results won't be satisfactory.

Thank you for your advice.


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 Post subject: Re: RCA 8x541
PostPosted: Dec Sun 03, 2017 8:23 pm 
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Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
Yes you could have the SMD on this model. Check the secondary voltage on IF cans while the static happens. If you see spikes of voltage you have SMD. Can be repaired cheap with some new caps after you remove the mica sheets.


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 Post subject: Re: RCA 8x541
PostPosted: Dec Sun 03, 2017 10:43 pm 
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Joined: Nov Wed 22, 2017 6:01 pm
Posts: 10
Thank you for the reply. So I would check the voltage across the secondary terminals of the IF, or from chassis to terminal on the IF? I am new to this and probably don't know some of the basics. But I am learning a lot.

I imagine there must be a write-up on this repair here on the forum somewhere.

Thank you again.


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 Post subject: Re: RCA 8x541
PostPosted: Dec Mon 04, 2017 12:05 am 
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Joined: Jul Mon 06, 2015 11:25 am
Posts: 170
Greg C wrote:
I imagine there must be a write-up on this repair here on the forum somewhere.


There are lots of helpful videos on YouTube showing SMD repairs. Just search for "SMD" or "silver mica disease".


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 Post subject: Re: RCA 8x541
PostPosted: Dec Tue 05, 2017 12:46 am 
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Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
Read with DC meter low scale from negative end from filter capacitors to secondary of of both IF cans. Any spiking DC reading indicates a voltage leak. SMD.


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 Post subject: Re: RCA 8x541
PostPosted: Dec Tue 05, 2017 2:47 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 2949
Location: Mountains of Mourne. Ireland.
Here's a go-to-video for... Replacing mica capacitors in an AA5 I.F. transformer.
viewtopic.php?p=2765766#p2765766


Should you require a couple of spares, both I.F. transformers can be found here $7.00 ea
http://www.oldradioparts.com/2a6fla.txt ←page was updated on January 1st, 2017 !

search for RCA 73036 and RCA 73037 on the above page using keyboard shortcut
Ctrl+F on a PC Cmd+F on a Mac

homepage: http://www.oldradioparts.com/


Schematic: http://www.nostalgiaair.org/Resources/243/M0015243.htm
high-resolution schematic: http://americanradiohistory.com/hd2/IDX ... e-0280.pdf

Greg.


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 Post subject: Re: RCA 8x541
PostPosted: Dec Wed 06, 2017 1:05 am 
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Joined: Nov Wed 22, 2017 6:01 pm
Posts: 10
Thank you very much!


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