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572B input impedance?

FL2100B Linear Amp was found to have a high input VSWR between 2-3:1 on 20, 15 & 10M bands.
With RF drive straight thru via Bird Thruline to 50 ohm dummy load I found VSWR was excellent at 1:1.
On inspecting the RF path taken (with key down with 800vac disconnected) via band switch and AMP tuning Pi network it was found to have a high VSWR on 14, 21 & 28MHz bands. Tuning those bands on input to Amp did little to achieve a low VSWR !!
Any suggestions would be appreciated to achieve a lower VSWR.
73s
 
Check bandswitch. Amazing how those cook when driven with a trashy radio. Could be bad cap, but with all of them reading high. I’m betting on harmonics arced bandswitch. Seen it many times
 
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