SB 220 problems....HELP!!!!!!!!!!

[John King]

Having trouble getting my SB 220 amp. going after some
changes.

Rectifier and metering board with bias circuitry board
in my SB220 replaced with a Harbach replacement board
which eliminates the Zener diode.

I now have High Voltage and the amplifier keys up.
There is very low idling current when keyed up. With
100 watts of drive there is NO output whatsoever. With
SSB drive, the grid current meter barely moves and the
plate meter does very little more. NO RF OUTPUT!!

Looks like the tubes are biased almost beyond cut-off.
Unkeyed there is only -1.61 vdc at E on the rectifier
board.When keyed up there is +6.1 volts at E on the
rectifier/metering/bias board.The bias supply is
providing 125 vdc to the relay. All wires going to the
rectifier/metering/bias board are attached to the
correct points on the board. All diodes and resistors
are wired in correctly.  Key-up produces only 40 ma.
of idling current and driving with 100 watts produces
no results.


Sounds unlikely that the relay is bad. It is
activating yet it is not putting the 125 volts on the
cathodes unkeyed.  Any expert trouble shooting
assistance will be appreciated. Please don't ask me
"is it plugged in". 73, John, K5PGW



 
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