[Amps] sb-220 tuning question - closing in

[Joe Isabella]

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 at 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
> 
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps


__________________________________
Do you Yahoo!?
Yahoo! Search - Find what you’re looking for faster
http://search.yahoo.com