From: "Gerry" 
Subject: RE: [drakelist] R4B hum

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Modern electrolytic capacitors do =
have a
certain amount of overrating but there is no reliable way to determine =
how
much. You would have to have the spec sheets from the manufacturer to =
give you
a better idea. Still I wouldn’t do it. You can never tell what =
line
voltage will do over time. Then there is temperature rise, another =
unknown. I
would suspect your B+ may be over the line at initial turn-on. After the =
tubes
warm up it probably falls to a lower and safer value. Manufacturers only =
say
their capacitors will perform up to a specified maximum voltage, after =
that,
you’re playing with fire (literally). As for hum, I would first =
make sure
the AF output tube is good. When my R-4B developed a loud hum, I tried a =
new
tube and that fixed it.

 

-----Original =
Message-----
From: =
owner-drakelist{at}www.zerobeat.net
[mailto:owner-drakelist{at}www.zerobeat.net] On
Behalf Of Mark Lakomski
Sent: Saturday,
October =
25, 2003
1:46 PM
To: John_K7FD;
drakelist{at}zerobeat.net
Subject: Re:
[drakelist] =
R4B hum

 





Hi
John,





 





I just restored an R4A that =
isn't
humming yet but that cap gets





very uncomfortably warm =
(and is
bulging) and am working on a 





substitute.  There are =
a few
other electrolytics but with a 100 





and 200 uf section on the =
power
supply I'd think it was most suspect.





 





I've seen nothing new or =

---