Here is an update on my 80 meter dilemma on my SB-200. Originally, I posted
that my SB-200 was working great on 40-10 meters but not good on 80. I had a
high swr and any noticeable power output above 150-200 watts immediately
dissipated.
The load and tune Caps (both the 100 pf and 500 pf caps) test good. No
apparent damage to bandswitches. The Plate choke looks good.
I inspected the tuned input C30 cap and added an additional 200 pf to the 470
pf mica cap. My swr on 80 meters is now much improved. I now have noticeably
greater output power BUT the power still quickly dissipates or diminishes
while keyed down. It peaks then quickly drops.
Are my grid-ground caps off both tubes suspect? I do have two well worn tubes
that show excessive heat damage. Can the 572B tube work great on 40-10 but
become dysfunctional on 80? Any ideas would be greatly appreciated.
Don
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|