[Amps] SB200 - RFC2 Replacement?

[carl seyresdahl]

Chris: From your info I suspect you had a parasitic hit. that choke should
normally be able to handle lots more current than the "normal" amount (200
ma . max.) I ould also suggest you get a kit from Rich Measures for
parasitic suppressors and mods for that amp. I have done this for several
SB200's and they all worked just fine. As for the choke itself I think R/S
should have them .. !!the kit above has several small changes that will help
stabilize the amp.
 Please note that I have no relationship to Rich other than as a satisfied
customer . !! the value of the choke is not too terribly critical except it
should be at least 25 to 30 or more uh. Thats all I can tell you at the
moment. !! Good luck with the repairs. Have a good day !!!!
  carl / kz5ca
----- Original Message -----
From: "Chris Allingham" <callingham@sympatico.ca>
To: <amps@contesting.com>
Sent: Saturday, September 28, 2002 11:29 PM
Subject: [Amps] SB200 - RFC2 Replacement?


> A friend of mine has loaned me his SB200.  If I can get it working again,
I get to use it (for a while anyway :=)
>
> From what he told me, and by inspecting the amp, it looks like RFC2 is
burnt out.  From what I've been able to gather from a schematic and partial
manual found on the internet, cut-off bias voltage from the power supply
bias circuit is applied through the coil of the T/R relay, a resitor, and
RFC2 to the grids of the tubes (on RX).  On TX, the Ant Relay jack grounds
the grids of the tubes through RFC2 and a couple of resistors.  (RFC2 is is
parallel with a 1Watt 3.3K resistor.)
>
> The schematics show RFC2 = 28uH.  How critical is this value?  Can I just
go through my junk box and use any old choke that's close in value?  Wind my
own?  If not, does anyone have a suggestment for a replacement part
(supplier, part number, etc)?
>
> Thanks in advance!
>
> 73,
>
> Chris VE3FU / VO2AC
>
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