[Amps] Old SB1000 built by me in 1988

[Ken Florence]

Hi Victor,
Thanks for the thoughts. It's done the arcing before sometimes, the band 
switch looks ok. Mine does not have the corona brass washer, but I thought 
that went into the 160 meter circuit off the band switch. I'll have to 
check. It's probably a good idea anyway since Ameritron did it on the 
AL80A. I'll have to give the capacitor plates a good luck.

Heath says in the manual you are OK up to 200 mils grid and 550 mils plate. 
I usually see the grid at about 150 mils and the plate at 500 mils.

Certainly something was wrong in the parasitic suppressor, but all seems 
fine now with the stock suppressor. Also works ok on 17 meters with the new 
plate choke. About 600 watts, but to be expected without a tuned input and 
specific output circuit.

It runs fine on 40 through 10. But figured I'd ought to figure what's going 
on on 80 before stepping up to 160.

Thanks again.

N3KF



On December 14, 2020 12:00:06 PM amps-request at contesting.com wrote:

> Date: Sun, 13 Dec 2020 22:04:44 +0200
> From: Victor Rosenthal 4X6GP <k2vco.vic at gmail.com>
> To: amps at contesting.com
> Subject: Re: [Amps] Old SB1000 built by me in 1988
> Message-ID: <7680a21d-34d6-3dfc-e151-93bab2de4027 at gmail.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Look at the band switch. The sizzling might be an arc caused by corona
> discharge. That is a common SB1000 problem and will destroy the switch
> if it hasn't already.
>
> There could also be an arc in the loading capacitor. Easy to miss that.
>
> Don't operate it until you fix it. Every arc burns something. Soon you
> lose your bandswitch contact or melt a bit of a capacitor plate into a
> blob that becomes a permanent source of arcs.
>
> I recall that there is one bandswitch terminal that is supposed to have
> a washer soldered on it below the lead to the tuning capacitor. It's
> important that it be there to reduce the potential gradient on that contact.
>
> How much grid current are you getting? Should be between 100-150 ma. If
> there is more, either it is underloaded or overdriven. Both conditions
> can cause arcing.
>
> ALC is not the best way to reduce the drive. If it is too slow, there
> could be an initial period of overdrive. Better to adjust the power in
> CW or with a whistle on SSB. Best is a "pulser" device.
>
> The measures suppressors don't do anything worthwhile and heat up on
> 10m. The stock suppressors are fine.
>
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> CWops #5
> Formerly K2VCO
> https://www.qsl.net/k2vco/
> On