[Heathkit] SB-401/HW 101 Final Questions

[Michael Waldrop]

The SB-400 and SB-401 both have the 10 ohm resistors. However, the HW-100
and HW-101 do not. The only bypass resistor in the HW-100 and HW-101 is
the 2.2 ohm 1 watt resistor from pin 6 to ground. This single resistor serves
both tubes.

The metering resistors on the HW-100 and HW-101 are the two 470 ohm
resistors on the meter switch, R921 and R922, behind the front panel. These
resistors are connected directly to the meter on the HW-100 but are connected
across the meter switch pins in the HW-101. Same circuit just a different
mounting method between the HW-100 and the HW-101.

If the metering resistors check good in the HW-101 but the plate current
soars full scale, do the finals arc? Also, when the plate current soars
full scale, does the breaker or fuse in the HP-23 trip or blow?

If this is true, I suspect the final tubes are gassy and the only fix is to
replace the tubes. You can't fix the gas contaminated vacuum in the
6146 by running the tube with only filament voltage for a long period of
time. The only fix is to replace the tubes.

73
Mike
W5RKL