[Amps] SB-220 flash over in power supply

Victor Rosenthal 4X6GP k2vco.vic at gmail.com
Sat Dec 14 10:15:07 EST 2019

Sorry. Here it is:

I've heard that RF can damage electrolytic caps, so it it a problem.
You might try paralleling a larger bypass capacitor at the bottom of the
choke. If you do that, you will notice a change in the tuning because
the choke acts like part of the tank circuit.
You could also add another choke with higher inductance after the bypass
capacitors, just to keep RF out of the power supply.
Just the thoughts of a non-expert.

Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5

> I am looking for some advice on some arcing I am seeing in the B+
> supply of my Heathkit SB-220. I never used the amplifier before I
> bought it at a flea market in Spring 2019. I have modified the amp to
> add 160m, following Rick Measures' (AG6K) excellent article in
> January 1989 QST.  Among the many things I did ti the amp, I replaced
> the stock Heathkit plate choke with the plate choke used in Ameriton
> amplifiers (part number 10-15197.  I thought was a better way than to
> winding my own choke. I now get 600w out of the amp on 160m with
> about 80w of drive on the Low B+ position (2kV).  I run the amp from
> a 110vac, rather than 220vac.  It will ultimately be used in a remote
> location where only 110vac is available. While keying in CW. I see
> sparks and flash-overs about 25% of the time. These flash-overs are
> between the leads of the filter caps in the B+ supply and the chassis
> wall of the amplifier. I suspect stray RF is the culprit.  I believe
> the Ameritron plate choke is sufficient, because it is used in all
> Ameritron amps that include 160m. So, what should I do to eliminate
> this arcing?  Would adding a layer of insulation on the interior wall
> of the chassis opposite the filter caps be enough?  Is this just
> applying a band-aid to cover up a more serious problem? I have not
> tested the amp on other bands to see if it happens there, too.  The
> primary use of this amp will be for CQ 160m CW contest operations
> from Labrador (VO2). 73, Dave VE9CB

On 14/12/2019 15:47, Ron W4BIN Youvan wrote:
> On 12/13/2019 11:35 PM, Victor Rosenthal 4X6GP wrote:
>> _______________________________________________ Amps mailing list 
>> Amps at contesting.com 
>> http://lists.contesting.com/mailman/listinfo/amps .
> I see no content, did you send it in text format?

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