Ameritron AL 811HX Problem
I installed (4) 572B Taylor MQ tubes which I received from rfparts in my amplifier.
On power on the plate current meter spiked negative and stayed there and the grid current
meter shows 170ma.When I switch to read HV it shows 1700v and 50ma on the grid current meter.
The link below is very similar but the opposite problem to mine.However I checked the grid resistors,
and shunt resistors and they are ok I will change D16 and the MOVs as mentioned in the post below.http://www.eham.net/forums/Elmers/197756
I immediately suspected the 572b tubes because the amplifier was working perfect before the change.
I re-installed the known good 811As and powered up with the same problem (all tubes lit up).
Disconnecting the anode caps the meters returned to reading their normal values, zero for plate current and
the same for grid current.
Close inspection of the 572b tubes reveal three loose pins on one tube,and a loose pin on two of the other
tubes and this did not happen with excessive force.(all tubes lit up)
Can anyone shed some light on what may have caused this problem and what the fix might be.
73 Paraic EI7IR