[Amps] SB-220 flash over in power supply

[Jim]

A .01 uf 6KV cap is available at Mouser. They are about 6 or 7 bucks 
though. They work perfectly for this. Not sure it will fix your problem 
though.



Thanks
73
Jim W7RY

On 12/14/2019 9:15 AM, Victor Rosenthal 4X6GP wrote:
> 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.
>
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> Formerly K2VCO
> CWops no. 5
> http://www.qsl.net/k2vco/
>
>
>> 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 
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>>
>> I see no content, did you send it in text format?
>>
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