[R-390] C-103 replacement

[Roger Ruszkowski]

Fred,
C103 was before the invention of hazardous oils.

The oil fill in R390 originals is mineral oil. OK and still safe after all these years.
 The ratio of core heat in the cap and the surface area required to meet cooling needs
when the room temp was over 110 resulted in oil filled caps. C103 has its own closed fluid cooling system half a century ahead of CPU coolers.

New technology has made much of this stuff a mote point.
We do not even think of operations temperatures for B+ filter caps these days.

More C is better at C103. You get a trade between how hard the cap pulls its inrush current.
The rectifier tubes have current limits. The 10 MFD was as big as possible with out over loading the rectifiers at power on surge.

New parts new internal parameters. Solid state the rectifiers with some robust diodes and add some more C to C103.

Less B+ ripple and a bit less receiver noise floor. A DB here and there and soon your receiver is no longer the choke point in you minimum discernible signal.


Roger AI4NI
 

-----Original Message-----
From: Fred Stillwell <fred.s43 at frontier.com>
To: flowertime01 <flowertime01 at wmconnect.com>
Sent: Tue, Aug 14, 2018 10:17 pm
Subject: C-103 replacement



  Roger,      Thanks for the advice on replacing C-103.  The original 10 mfd. 300 VDC


oil filled cap isn't leaking but  I'm not sure about the type of oil GE used in that part.


  I'll follow your suggestion.


73's  and thanks again,


Fred Stillwell
AA8S