[MFJ-Ameritron] Ameritron AL-80B problems

[KOCQW]

My AL-80B quit working on the traffic net on 75m it has no output.

When the amp is turned on now the grid will read a negative number and the=
 plate 
runs at 175 this is with NO rf going into the amp and it is not keyed up. =
The HV runs 
at 2700 volts.
This will last only a few seconds then the grid and the plat go to zero an=
d the HV will 
go to a normal  of 3000v.

When it stoped working it looked like the tube was glowing as it never has=
 done
before.

The HFradio had high SWR on the radio meter and would not transmit rf unti=
l the 
amp was put in STBY.

It has the protection board installed.

Any thoughts?

Thanks de John K=D8CQW