[Amps] Old SB1000 built by me in 1988

[Victor Rosenthal 4X6GP]

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 13/12/2020 20:53, Ken Florence wrote:
> Hi all,
> After a long time of having an intermittent no power out problems on my 
> amp, I finally figured out the problem was the parasitic suppression 
> circuit. I had put one of Rick Measures (SK-RIP) Nichrome kits in it. 
> Not sure if there was a solder joint issue or what, but went back to the 
> stock suppressor, replaced plate choke (original with resonance issue on 
> 17 meters) and it works fine.  At least 40 through 10. I notice when I 
> tune it up on 80 meters I get a quick sizzling sound sometimes (very 
> short duration). I assume that is an arc? I need to get the ALC line 
> back on cause it's obvious it only needs about 75 watts input for full 
> output. New Graphite tube. Have not tried 160 yet.
> 
> So could it be a little over driving it on 80 that is causing that, or 
> if not, how do I narrow down where it is? Definitely nothing burnt cause 
> I went over it with a fine tooth comb.
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