[Boatanchors] SB-220 in AM service

[rbethman]

Looks like we are finding the SAME results!

The only thing different in the LK-500ZB would be the PW Dahl XFMR in 
the power supply.  I've NEVER smelled anything from the power supply.

GO FOR IT!

Bob - N0DGN

Jim Wiley wrote:
> I use an old Drake L-4B in AM service, and have used it for more than 
> 20 years, with no failures - and the same set of tubes.  I usually set 
> it for about 350 watts unmodulated  carrier output (the max allowable 
> is 375 watts, which which with modulation equals 1500 watts PEP).  I 
> tend to be long winded, but the L-4B is a continuous duty rated amp, 
> and was built properly.  It has a pair of 3-500Z tubes, a squirrel 
> cage blower, chimneys on the tubes, tube sockets in a pressurized 
> plenum, plus a separate power supply that can really take some guff. 
>
> The SB-220 should be OK at  250 watts  or so out, as long as you limit 
> continuous talk time to 10 minutes or less , with no more than a 50% 
> overall duty cycle. Keep your eye (or nose?) on the transformer - if 
> it starts to smell hot, back off on the talk time.  For a test, I ran 
> the L-4B on 20 meters at 1000 watts output  for a hour into a dummy 
> load - other than the power supply starting to smell a bit warm,  and 
> the tubes getting sort of orange, no problems.
>
>
> Before the rules for AM changed, I used to run it at about 400 watts 
> carrier output, mostly on 10 meters AM, also with no problems.  
> However, I did manage to unsolder the connections inside an external 
> low-pass filter doing that. 
>
> Good luck.  Maybe I will hear you on  the band once I get my 10-meter 
> antenna back up.
>
> - Jim, KL7CC

-- 
Bob Bethman/NØDGN/BC-610/Northern Radio 
SP-600 Manassas, VA - MultiBand Dipoles