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Post subject: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 10:12 am
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Roadie
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Anyone ever had to remove this trimmer (mylar?) in a Silvertone? If so, which value cap worked out.

Thanks for any input,
UN

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Post subject: Re: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 10:34 am
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Rock Star
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Looks like a noise-oscillator reduction setup (coupled with resistor and fixed cap) --- maybe leftover technology from their receiver-tuners.

I hope it works, as I have no idea where to find one, even with the proper pico-farad range.


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Post subject: Re: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 12:09 pm
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Rock Star
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From DIY board...

"That's referred to as a "mica compression trimmer." The value might be printed on it. If not (and if you can't find the original schematic or parts list with the value), you'll need to remove one end from the circuit, compress it all the way and measure the pico-farad value. If you need a replacement, Nebraska Surplus has dozens of them.

Incidentally, that's a very unusual application for a trimmer cap. I have to wonder if it was intended to "tune out" an oscillation. If that's the case, I'd remove it and reconfigure the circuit and/or wiring layout to stabilize the tube.

The solution might be as simple as adding a grid or anode stopper, or a ferrite bead."


https://www.surplussales.com/Variables/ ... pCap1.html


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Post subject: Re: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 1:00 pm
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Roadie
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Joined: Sat Dec 13, 2014 7:34 am
Posts: 245
It's gotta be for oscillation. It's 10pf - 80pf and it only works occasionally. I found one online but I may be better off finding a cap value that works and just replacing it with that. I may just pull one end and see what happens.

Here's the schematic
Image



https://www.westfloridacomponents.com/T ... PC462.html

UN


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Post subject: Re: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 1:10 pm
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Rock Star
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That's what I'd do. Go for 80-100 pico-farad, 300-400VDC rated ceramic disc cap.

https://www.mouser.com/ProductDetail/Mu ... OsQBf3A%3d

Happy Turkey Day!


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Post subject: Re: Silvertone 1431 trimmer question
Posted: Wed Nov 22, 2017 1:27 pm
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Roadie
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Joined: Sat Dec 13, 2014 7:34 am
Posts: 245
Thanks for the info BMW, I've got a couple of 100pf silver mica's. Happy Thanksgiving to you as well, I've been cooking pies all day!

UN


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Post subject: Re: Silvertone 1431 trimmer question
Posted: Fri Nov 24, 2017 7:04 am
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Roadie
Roadie

Joined: Sat Dec 13, 2014 7:34 am
Posts: 245
Lotza conflicting data on a 6X5GT input capacitor. 4uf, (32uf on Mullard sheets), can't find a solid max rating. This Silvertone has a 10uf/450v input cap. I can't see any reason why a 16uf (which I stock) would create a problem, but I'm a little little leery given it's reputation and my limited experience with this rectifier.

Note - A Silvertone model 1333 uses a 6X5 with a 16uf input cap and a 2.2k dropping resistor.

Any thoughts?

UN


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