Bias setting, and S Meter zero adjustment. On the HW series, these controls are
accessed through openings in the right side lower cabinet.
The HW series uses a builder assembled VFO with a circular dial and frequency
calibrations every 5 KHz. The dial reduction drive consists of two Jackson venier drives.
The SB series used a preassembled LMO with a circular dial having calibration marks
every 1 KHz. The dial reduction consists of a pinch pulley that engages a metal ring on
the inner surface of the circular dial.
The HW series uses slide switches for the PTT, VOX, CAL function and metering
selection. There is no provision for metering grid current or the High Voltage in the HW
series, and of course the switch for frequency control using an auxiliary crystal or LMO
is not present.
The HW series does not provide a CW sidetone volume adjustment nor an adjustment
for the relative power meter reading. The HW series does not support the AUX XTAL
control or external VFO control and components and wiring associated with these
functions are not present on the associated circuit boards (although in most cases, the
printed circuit traces and associated mounting holes are present).
a.3.1. RF Amp and 1st Receiver Mixer
The SB-100 and SB-101 do not use the 6HS6 tubes in the receiver's RF amplifier, V10,
and receiver first mixer, V11 but rather uses 6AU6s in both stages.
The SB-102 uses the 6HS6 but ONLY in the receiver's RF amplifier, V10.
Like the SB-100 and SB-101, the HW-100 does not use 6HS6 tubes in the receiver's RF
amplifier (V10) and receiver first mixer (V11) but rather 6AU6s in both stages.
The HW-101, however, used 6HS6 tubes in the receiver's RF amplifier (V10) and
receiver's first mixer (V11).
At any rate, if the 6HS6 tube fails, the 6AU6 can be directly substituted without any
changes in circuitry.
The circuit design the 6HS6 tubes were used in operated the 6HS6 tube at or, in some
cases, exceeding the tubes ratings. This is one reason quite a number of the 6HS6
tubes failed sooner than they should. There were other tube problems that also
contributed to early tube failures such as some 6AU6 EL-MENCO tubes had 4 volt
filaments instead of 6 volt filaments.
I found that both V10 and V11 (receiver RF amp and receiver first mixer) would fail,
short internally. The symptom was complete loss of sensitivity, no signal received, and,
in many cases the shorted tube resulted in a very strong 20 over 9 meter indication
HW & SB History revised 12/17/2021 Page 17
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