"static" signal that occurred with or without the antenna attached. Replacing the
defective tube(s) eliminated the problem. I experienced this problem in one of my HW-
101s. Turned out both V10 and V11 were both shorted internally.
The price of a 6HS6 is a bit steep, $18 (www.vacuumtubes.net price), higher
(www.vacuumtubes.net price). Both tubes are available, depends on which outlet you
use and whether you are willing to pay $18+ for one tube. I personally use 6AU6s but
you may think differently.
a.3.2. SB-101/SB-102 LMO Power Source
Power sources for the SB-101 and SB-102 LMO's are entirely different.
The SB-101 LMO power source is regulated 150VDC from the 300VDC source on
pin 3 of the 11 pin power socket.
The SB-102 LMO power source is also regulated, "+10VDC", and the power source is
from the filament supply through a #1815 dial lamp, 56 ohm resistor, zener diode
(D907) and a 2N3567 transistor used as a regulator.
The wiring to the FREQ CONTROL switch is a bit different as well.
a.3.3. Sideband Bias Circuit
The sideband bias circuit is similar but different between the SB-101 and SB-102. There
are series resistors with the bias voltage source in the SB-102 that are not in the SB-
101.
Personally, I would not even consider using an SB-102 LMO in an SB-101. Messing
around with swapping LMO's could result in instability that you didn't have before.
a.3.4. Accessory Socket
The SB-102 has a rectangular socket at the rear the permit connection of a two-meter
transverter. This is not present on the SB-100 or SB-101.
There is also an accessory socket on the HW-101, but not on the HW-100
a.3.5. CW Filter
The SB-100 and HW-100 do not have the hardware and switching mechanism for the
CW filter. It looks like this could be added by using parts from a junked HW-101, but I
have not verified this.
HW & SB History revised 12/17/2021 Page 18
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