Dan,
The plates should get red when the amp is keyed for a while. If they turn very
bright orange,
then be concerned. It sounds like you had the amp under-loaded, which can
cause it to spit &
sputter. What was your loading C set to?
When I tune my TL-922 (very closely related to the SB-220), I do a quick "rough
tune" carrier at
low drive power, then apply full power using my rig's keyer sending dits at
30wpm. I now pretty
much know where the amp should be set on my favorite parts of the bands, so I
can usually skip the
first part.
Are you sure the bandswitch is in good shape? When I bought my amp, the switch
was torched.
Joe,
N3JI
--- Dan Sawyer <dansawyer@earthlink.net> wrote:
> All,
>
> I am closing in on 'tuning' an sb-220. To make a long story short I was
> tuning at low power and running it at a higher power. Now I am tuning up
> incrementally in 3 steps from 10 watts to 100 watts CW. This works
> smoothly on both 80 and 40.
>
> However on 20 when I finished the a 3rd tuning cycle of optimizing
> 'tune' and then 'load' I turned off the exciter drive. Upon re-engaging
> the exciter the amp went ballistic; the sound was a loud continuous
> spitting. It was continuous, not a single snap or pop. I backed the
> power off and re-tuned following the same steps and after turning the
> exciter off and then on it did the same thing. I waited about a second
> looked around the side of the amp. The tube plates were glowing dull
> red. I was able to prevent this by carefully de-tuning. However this was
> more by feel then by a plan.
>
> What is most likely happening??
>
> How can it be prevented??
>
> Thanks,
> Dan
>
>
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