1939 Stromberg-Carlson 450M Radio Repair Journal and Photos
by Chad Hauris, Retro Electronics and Audio Lab, Midland, TX. 11/12/06

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This S-C chassis was left on our doorstep by an unknown donor. We really appreciate it as it is a very high performance set. It has a motorized tuning system which can be pre-set for different stations. There was no cabinet with the chassis when we got it, and most of the tubes were missing.


Replacing capacitors in the radio chassis.


New capacitors installed. A new power cord and fuse holder were installed along with a filter choke to substitute for the old field coil speaker. A new tube socket was also installed for one of the 6V6's. The tuner gear motor can be seen at the left. We also installed a new volume control.


Testing the chassis. The transformer being tested as a field coil substitute began to get hot so a larger choke was needed.


Front of completed unit.  The knobs were salvaged from an old Magnavox console.
The controls from left to right are: Volume, Tone, Bandwidth, AM/SW band, and Tuning. This set has a variable bandwidth and is capable of reproducing a lot more "highs" in music than most AM radios.


Top of chassis. The motor preset unit is at the rear of the tuner and has pins that can be moved to activate contacts to stop the motor at desired stations according to a pre-set button. The motor runs fine but we have not set up the presets yet.


Top view 2. The new filter choke is mounted at the left rear.

Tube complement:
6K7: RF Amp
6J5: Oscillator
6A8: Converter
6K7: IF Amp
6H6: Detector/AGC
6SQ7: 1st audio amp
6SQ7: Phase Inverter
6V6 (2): Audio Output
5Z3: Rectifier

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