640b e-cap values - Printable Version

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+--- Thread: 640b e-cap values (/showthread.php?tid=24165)

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640b e-cap values - WyTex - 03-03-2023

Morning guys -

Found this nice looking Philco at an antique shop last month and decided to bring it home as a birthday present to myself.   

https://philcoradio.com/library/download...l.%201.pdf

After rebuilding the bakelite blocks, checking resistors, tubes, etc, this set has hum that does not change with volume.  As I was about to swap out tubes one by one I noticed part #68, a 3 part electrolytic can on top comprising 2mfd, 2mfd and 1mfd e-caps.  I missed this and suspect it could be the hum source.  Been unable to locate these value electrolytics so far.  Are there alternatives for 1mfd and 2 mfd, 450v caps?  AES has these but only at 50v rating.  

Looking for guidance.  
Thanks very much fellas,
Paul

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RE: 640b e-cap values - Brad Winder - 03-03-2023

Good morning Paul,

Yes, that will be the source of the hum issue. Because of their low value and where they are used in the circuit, you could use non-electrolytic caps. But JustRadios and Sals Capacitors both carry 450v electrolytic caps in 1 and 2 uF sizes.

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RE: 640b e-cap values - morzh - 03-03-2023

Paul,

I have always been able to rebuild the multy-section electrolytics.
And, as Brad noticed, because of where they used and their values, you do not have to worry about the ripple rating and the temps, so use any reputabe mfr electrolytic caps, and they should all fit nicely inside this cap, and they have the common GND lead, so easy to do.

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RE: 640b e-cap values - WyTex - 03-03-2023

Finally. Hum is so hard to troubleshoot for me.
Thanks very much Brad and Mike.

Paul

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