[Amps] More information for "What NOT to buy"..

[Tom W8JI]

> have kicking around.  Of course when I buy an Sb-220,  the 
> band switch is not
> my concern so no sweat.  I have had several Drake  L4B 
> amps and never did I
> see a bad band switch on one of them.  Even the  Dentron 
> and Amp Supply amps
> have better band switches.

 The switch in the SB220 is exactly the same wafer style and 
manufacturer as in many Dentrons and Amp Supply amps of 
similar operating HV.
That switch is good for normal mistuning at about 3000 volts 
maximum supply voltage.

Amp supply and Dentron did use some larger JV-9000 series 
switches, but not as a general rule in 3000 volt and lower 
amps.

> As to why they burn  up?  well that discussion could
> land you in jail :-)   The 2  Sb-220 amps that I actually 
> ever used on the air
> I bought as kits and built  myself so I knew the condition 
> of the band
> switch.  I used an Sb-220 for  many years and got good 
> service form it.  Careful
> tuning kept it in good  condition.

Bingo. Careful tuning implies the HV is not extreme.

See:

http://www.w8ji.com/demonstation.htm

73 Tom