AL-811H problem/ question

[Crambone]

I acquired an AL-811H from a friend but he said it had some issues so I did the following. Its wired for 220 so first thing I did was check to see if wired properly and check fuse values, all good. I pulled the tubes and tested continuity between pins and found one with a filament to grid short. I pulled the tube sub chassis out and found the grids are wired directly and it looks proper. I ordered 4 new 811A Pent Lab tubes to be on the safe side. I cleaned all the switches, contacts… and re-assembled. I left the tubes out and brought up on my 120v variac and all voltages checked good and no smoke! So I powered off and plugged into 220 and fired up again with tubes in and let sit for 1hr in Standby, checked all voltages …. And all good. I then tuned up on 40 Meters AM at 10 watts and looked good so slowly brought up power to 50 watts and HV is 1750 and Plate is good but grid meter pins?
im not sure what’s causing Grid Meter to pin anything I can check?

KB2LMN

 

[338_MtRushmore]

12.) Grid meter pins with low drive power

• No plate current
  • Open RF plate choke or no high voltage
• Low plate current that does not change with tuning
  • Open tank circuit feed, open blocking capacitor
• Normal plate current and output, but grid meter pins hard
  • Open grid shunt R8 1.5 ohm
    • Can be caused by filament to grid/ground short or tube forced in socket wrong
• Low RF power output
  • Loading control too far meshed, load capacitor shorted, or antenna system bad
• Also see 1 and 2

Ameritron AL80B AL811H AL572 Amplifier Trouble Shooting

 

[BayouRadioAmplifier]

I got one of them. have melted 811 plates. popping the AC input fuses.
popped some of the resistors in line with the grids. etc.
(yes, I need to ground the grids directly some day!)
.
but a friend sent me some old Russian made 811's and
it has been working great since then!
.
make sure your LOAD control knob at position 10 has that variable
capacitor about fully opened. lowest capacitance.
.
put the LOAD control at 5. drive the amplifier with about 15 watts or so,
and peak with the TUNE control. notice the output power level.
then turn the LOAD to 4.5 or so and retune. check for more power
output. and go down some more, until you have about 10 dB gain.
15 watts in for about 150 watts out. check grid current.
this will get you close to proper tuning. then go to about 70
watts in for 700 watts output. do this real quickly.
give the tubes a rest. it is good to turn the LOAD control
back to a higher setting, higher number, (clockwise)
less gain, and a lower impedance at the plates, less voltage
there, less chance of arcing. and always the TUNE control
to peak it up, last.
.
on my 811H the LOAD is usually around 3 to 4 on all bands.
peak with the TUNE last... yes, tune with the TUNE control last.
works fine. I peg the grid meter a little in SSB mode.
.