Re: power and mic wiring

Bob Lunsford

Original caps are indeed "unobtanium" but replacement caps
are worlds ahead of the old technology. I had a Swan 350
about ten years ago that I bought at a hamfest. Plugged it in
and the power supply caps were beyond saving and one
blew up and it sounded like a shotgun shell going off.

There are some who advise putting a variable AC transformer
in the circuit and bringing it up slowly "to polarize the caps" but
while this may work, better is to do as suggested: Make a list
of the electrolytic caps and plan on replacing them.

Some have suggested putting a 100-250 W lamp i series with
the AC so the AC is limited. Might try it but it is a trial and error
situation where error is most likely and proves to be a waste of

I had a Philco 650 back in the '50s that had a shorted bypase
cap on the power output tube from screen to ground. It was not
an electrolytic. This proves that it could be any cap. The electro-
lytics are polarity sensitve and putting one in backwards as far
as polarity is concerned is like inviting a short and immediate

Go slow, take your time. Some of those old radios were superb
as was the Philco I had.

Bob — KK5R


On Tue, 1/1/19, Mike Lichtman via Groups.Io <> wrote:

Subject: Re: [BITX20] power and mic wiring
Date: Tuesday, January 1, 2019, 8:23 PM

    On the 30’s radio,
replace all the caps (especially the electrolytics) 
before powering up again or you may burn up the power
transformer. They are usually “unobtanium”. 73 Mike

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