[Amps] SB-200 80 Meter Dilemma Update

[R.Measures]

>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. 

**  This suggests that your drivermight be throttling back to protect 
itself.
>
>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. 
>
**  strange

>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? 

**  No. 
-   I would try a Pi-network 80m tuned-input with a Q of 2.  (Xc!=25-ohms)

good luck, Don