SB-200

[Mark Graalman WB8JKR]

  The only thing that would cause R12 to open would be
a large current draw from the B+ supply such as an arc
in one of the tubes, or a short in the B+ supply.
 If the unit hasn't been in use for a few years the tubes
*may* be a bit gassy. I would suggest at any rate installing
about a 10-15 ohm 10 watt resistor in series with the B+ to
the tubes, and a pair of back to back connected diodes
across the multimeter to protect the movement.
 Those 33 ohm resistors are not fuses, they are intended to
balance out the operating bias between the tubes
from grid current draw.

Mark  WB8JKR

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