[AMPS] Parasitic suppressors/another question,

[Dick Green]

W5AH wrote:

> In the 220s Ive worked on with bandswitch damage that damage
can be directly attributed to the operator rotating the band switch
instead of the load control while tuning up.  The physical layout
of the tune, load and bandswitch controls makes it easy to turn
the wrong knob and cause the "parasitic" damage.

Yes! It's about time somebody brought that up. I can't count the times I've
reached for the wrong knob on that amp. Luckily, I've never turned it far
enough to break contact, but I can see how that could happen easily in the
heat of a contest. There really is not that much difference in mechanical
resistance between the Load and Band knobs, so you don't get much physical
feedback before it's too late.

Seems to me that we have reasonable alternate explanations for all of the
symptoms attributed to parasitics in the SB-220:

1. Burned-out band switches caused by accidentally turning the band switch
while tuning.
2. Cooked suppressor resistors caused by pushing the amp to the max (1200W
CW @SSB position).
3. Arcing at the Tune capacitor by over rotation of the Load capacitor (easy
to do.)

Hmmm. Operator error in all three cases. What a surprise. Are there any
others we can add to the list?

Thanks for your post, Bob.

73, Dick, WC1M



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