Harvey Wells Bandmaster
TBS-50C Modified to 50D and Restoration
Harvey Wells History
Harvey Radio Laboratories
12 Boylston St., Brookline, MA
Southbridge, MA (1940)
Founded:1933 Closed:1968 Production started:1933
In 1940 Clifford A. Harvey (W1RF) and John Wells (W1ZD) joined and started the Harvey-Wells Electronics company in Southbridge, MA. The company was previously known as Harvey Radio Labs. Harvey-Wells produced 85% for military purposes and they where awarded the Navy “E” award for excellence during WW II. The famous Harvey-Wells TBS-50 first appeared in QST of 1948. In 1957, the company has been acquired by "Within Machine Works", the "Harvey Radio Labs" company still existed and became owner of broadcasting stations.
My Bandmaster TBS-50C Restoration Project
(Click any photo to see a larger view)
I don't recall where my TBS-50C came from. It was given to me from some estate many years ago. It set on the shelf for years before I finally decided to restore it in early 2020. My first project was to build a power supply for it as documented here. The Bandmaster had a very good front panel. The only change was the addition of an HC6 crystal holder by a previous owner. Internally it had seen some wear but after a cleaning and removal of some previous mods it was ready for my restoration.
The home-brew power supply I built was designed around the original Bandmaster AC supply but differs in several ways. I do not switch B+ in the supply. It is always sent to the transmitter which is modified to have a combination antenna and B+ relay keyed by the transmit/stand-by switch or PTT from the mic. The supply is choke input and provides around 400V B+ at 200ma. This is slightly less than the recommended maximum voltage but it was the best combination transformer I had and with old wiring I thought it would be better to keep the voltage on the lower side. This lowers the transmit output power slightly. There is no difference at the receive end between 18 watts and 25 watts so don't sweat that! The supply uses an 8 pin female octal socket wired like the original except for the PTT pin which instead is 17V DC output to the transmitter to power the relay and also the class D audio amplifier described later. This low voltage DC is derived from a series connection of the 6.3VAC and unused 5VAC windings rectified and filtered.
Whenever I look at a restoration project I always have in mind improvements to the original design. Looking at things that were designed 70+ years ago you often think "why did they ever do that!" or "there is a much better way to do that." In the case of the bandmasters there are several things that fit those thoughts. I would never touch the front panel but otherwise the design is always up for improvement.
This was a TBS-50C which is the carbon microphone version. I even have several of the original carbon microphones used with the TBS50. The transmitter however was missing the microphone input transformer and while I could have replaced it my thought was that no one would like to hear a carbon microphone on the air today. So I added a class D amplifier and a backwards push-pull audio output transformer to drive the 6L6's which were actually replaced with 5881's. An aluminum panel was formed to hold the small class D amplifier and the modulation pot which lines up nicely with the original hole on the right side of the case.
An antenna relay was added which also switch B+. This relay is keyed by the transmit/stand-by switch in CW mode and either the transmit/stand-by switch or the PTT in Phone mode. Two BNC connectors were added to the back panel for antenna and receiver connections. Several components were replaced and/or moved to more appropriate locations. B+ was removed from the final tank circuit and a wafer was added to the band switch to add needed capacity on 80 and 40 meters.
Harvey Wells Radio Links
This page last updated 5/22/2020
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