Good comments. The Heathlkit manual actually says to turn on in low power
(CW) position.
On Tue, Oct 8, 2024 at 1:25 PM Dennis W0JX via Amps <amps@contesting.com>
wrote:
> All: My 1977 SB-220 works great on all bands, including the WARC bands.
> There is an issue on 30 meters where there is not enough loading capacity.
> I added a two doorknob caps of 35 pf each in parallel across the output
> capacitor. They need to be the proper NPO types that can handle the
> current. Of course, this results in the loading capacitor being set to a
> smaller amount on the highest bands (20, 17, 15, 12, and 10).
> As far as the input goes, the tuner in my K3 handles it just fine so I did
> nothing different with the input slugs.
> One BIG thing I did was to pull out the RF chokes and capacitors from the
> grids of the 3-500Z's and directly ground the grids to the chassis with
> wide copper strips.This resulted in the amp being easier to drive on all
> bands. I get about 1 KW out on 10, 12, and 15 meters and a bit more going
> lower depending upon my line voltage. This is with the original tubes from
> 1977!
> One thing to check is to make sure that your parasitic suppressors are in
> good working order, i.e., that the scrawny original carbon resistors are
> not cracked or way out of specification.
> I love my SB-220 and it is my go to amp for most of my operations even
> though I also have an ACOM 2000A and AL-800H. The ACOM is used for
> contesting and rapid band changing and for 160 meters when something
> interesting comes on the air.
> As far as the soft start issue, I chose not to install it. I ALWAYS turn
> the amp on in the low power position. I think that the 26 ufd filter caps
> don't create a huge current surge - I also replaced the PS diodes with 3A
> 1000 volt units.
> 73 Dennis W0JX
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