[R-390] R-390 C101 and C103 Caps

[Roy Morgan]

On Jan 3, 2009, at 11:06 AM, Perry W. Remaklus wrote:

> I am working on a R-390 and C101 (10uf 600VDC B+ filter) and C103  
> (10uf 300VDC audio decoupler) are both are leaky --- both are paper  
> in metal cans.

Perry,

The main B+ fiter cap in the R-390/URR is an oil/paper cap.  I'm  
surprised that  you find it leaky.. they very seldom fail or leak.   
If  you replace it with an electrolytic, that will work just fine.  Be  
sure the voltage is high enough.  The surge voltage on that cap will  
happen before the series regulators get heated up, so a quick  
measurement at turn-on will be needed to find out what you need.  Here  
is where the DVM is best set aside and a VTVM with moving needle used.

Roy


>  I can locate a poly cap for the audio decoupler but it is expensive  
> (Cornell Dubilier UNL series Electrofilm Metallized polypropylene).  
> Would a much cheaper electrolytic work here?

Film caps of that value are simply not needed in that spot.  Use  
electrolytics.

Get good caps at reasonable prices at:
http://justradios.com/

Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073