K3MSB

TBW-4

TBW-4 Rectifier Modulator Unit and HF Transmitter

--





HF Transmitter Transit Case

-- -- --

-- --



TBW-4 HF Transmitter

-- --

The TBW-4 is in clean and stock condition. There is nothing missing! Mike did a slight rewire of the output circuit to act as a tuner for another transmitter, and this can be seen by the extra SO-239 hanging off the capacitor in the upper deck. The oridinal disconnected wire was just moved out of the way and it will be easy to remove this modification.
-- --

-- --

-- --

-- --

-- --






TBW-4 Rectifier Modulator Unit

The RMU was stored without a transit case so it will require some cleanup. What I was delighted to find was that it is also in stock condition and only missing the HV and Filament transformers. Since these are 800Hz transformers, that is not significant for me.
-- -- --

Having the RMU is important for a realistic restoratoin for a couple of reasons. First, the plate current meter is the top left meter (center photo above). Second, the Emission switch, mic, and key jacks are at the bottom of the unit (below left photo). You can certainly use a TBW with an RMU, but you have to provide these things yourself.

Note also in the above center photo the dual line voltage / PA Filament voltage meter. This is an 800 Hz meter and I have been told it will work reasonably well at 60 Hz with the voltages reading a bit lower than expected. I plan to leave this in the PA Filament position to give me an indication the PA filament voltage is enabled. But first, of course, I'll test the meter to see how far off the voltage reading really is.
--

The below left photo shows the 843 based modulator on the top deck of the RMU. All the parts are there, and they don't care if I'm powering the unit by 60 Hz or 800 Hz! I am hoping those transformers are still good!

The below right photo shows the middle deck and it can be seen that the Main Plate Transformer T-201 is missing.
-- --

The below left photo shows the lower deck and it can be seen that Filament Transformer T-202 is missing. The transformers behind where T-202 should be is the Low Plate Transformer T-203.

The below right photo shows the back view of the upper deck and the modulator.
-- --

The photos below show more back views of the upper deck (left, center) and the middle deck (right). In the center photo input transformer T-205 is to the right of the 843 Speech Amplifier Tube while Modulation Transformer T-204 is to its left. The right photo shows both 1616 High Voltage Rectifiers and the 5Z3 "Aux" rectifier tube..
-- --

-- --

-- --

-- --

--

Copyright (c) Mark S. Bell 2021