Harvey Wells conversion TBS-50C (Bandmaster Senior) to TBS-50D (Deluxe)

[ns7h]

Does anyone have a copy of the directions from Harvey Wells on their conversion kit for the TBS-50C to the TBS 50D?  I have the components on the TBS-50D conversion but would like any cautions,  precautions that the factory has.  My conversion would be an outboard chassis with connections for HV, filaments, shielded audio and ground.  Not determined is if I would have relay control for which audio stream is active - carbon mike or high impedance.  Cool to switch to see difference on the air.

The Bandmaster manual stated that the instruction sheet for the kit was CMA-50.  I have not found it in any searches I have done to date.

Thanks for the help.

NS7H

[MikeKE0ZUinkcmo]

I don't have the doc you're looking for but the schematic below is their "D" schematic, redrawn.   I would switch the two speech amps at the grids of the 6V6s.   I used this same speech amp when I refurbished a TCS 13 Transmitter.

Mine was a "C", but when I bought it as a basket case, it had the Hi-Z speech amp chassis in the basket as well.   I just stripped it and put in new components per the schematic.   Didn't even swap out the original electrolytic can, and all has been fine.   I used some RG-174 coax to run to the modulator grids.

Hope you find the document you're looking for.

[ns7h]

Thanks Mike.  Still no joy on a manual for the kit upgrade to TBS-50D.

My manual has the schematic for the preamplifier, however I have no voltages for this stage that states the ratings of c4, c5, and c9.  It looks like several dropping resistors from the power supply B+ so it should be less than 400V.   I am hoping that I don't have to connect caps in series and I can use a can I have that has the correct capacitance with a standard 450 V rating.

What values does your preamp have for the voltage level for these capacitors?

Thanks , Bob

[N3GTE]

450v caps should be fine as the stock p/s delivers about 435v. Here's something else to do w/a TBS-50 or C model https://www.swedeart.com/harvey/html/tbs-50.html

Terry N3GTE