[Amps] SB-220 Bandswitching

[Pete Smith]

I believe it has been suggested before on amps that it's a good idea to replace the bandswitch knob on the SB-220 with one that is very different from the two capacitors - maybe a large bar knob, for example - as an aid in avoiding 4AM problems.

73, Pete N4ZR

At 07:37 AM 6/4/2006, W2RU - Bud Hippisley wrote:
>Peter Chadwick wrote:
>> In my innocence, something puzzles me. Is the indexing on the SB220 bandswitch very weak, or are the capacitors very stiff?
>In my opinion, the former is true -- on *my* SB-220, at least.
>
>>  I would have thought that the resistance to turning of the bandswitch would be sufficient to tell the operator that he (or she) was attempting to turn the wrong knob before it actually moved.
>>   
>Peter, I think the problem is compounded by the fact that there's some 
>initial "stiction" when first trying to turn the capacitors.  I just did 
>some experimenting in response to your posting, and I find the force 
>needed to get the capacitors to start moving is extremely similar to the 
>force needed to turn the bandswitch -- especially if the capacitors 
>haven't been turned recently. 
>
>Also, when operating a contest and/or suffering from lack of sleep, 
>there may be no rational reason for turning the wrong knob -- just a 
>"foggy" head doing dumb stuff.  In my shack, the amplifiers are off to 
>the side so that I'm seldom looking in that direction "in the heat of 
>battle".
>.
>> What size is the bandswitch? Is it the one with centres about an inch and a quarter apart? If so, it's pretty marginal at 1 kW: the KW1000 amp from KW Electronics in the UK used that size switch, but had a phenolic shaft to get the voltage rating up.
>>   
>Sorry -- can't help with answers to those questions.  However, I *will* 
>say that my SB-220 seems to have too *little* bandswitch detent 
>resistance whereas my Amp Supply LK-550 has too *much*.  In fact, I can 
>envision a time later in my life when arthritis or gradual infirmity 
>will make it impossible for me to change bands on the Amp Supply unless 
>I add some mechanical advantage to the present knob or wait for the home 
>health aide to arrive... :-) .
>
>Bud, W2RU
>_______________________________________________
>Amps mailing list
>Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps