According to Penson's book on Heathkit amateur radios, the initial
design for the LMO was done by Shafer, and was built by Elrad Engineering.
As the SB rigs became more popular, Heath got other unnamed manufacturers
to make the LMO, I think mostly to keep Elrad honest. In the end,
TRW made the bulk of the LMOs used in the SB series.

The VFO in the HW100, and HW101 was always solidstate.

-Chuck

Jim wrote:
Well The LMO (tube type) in my SB-101 was made by TRW(stamped on the
case) , and so is the solid state LMO in my SB-102. The solid state
unit doesn't have any FETs in in just 2N706 transistors with a single
RCA 40080 output transistor.
It was also made by TRW. (the schematic for the solid state LMO is
available at bama.sbc.edu and it's mirror site).

Does anyone have the schematic of the Tube LMO?