Rescue project for a Studebaker Transtar radio AC-2971 for Brian Dahl
Cost To Date
Tubes, TubeDepot, $23.75 Tube, VacuumTubes, $10.00 Filter Caps, Digikey, $2.05 Filter Caps, Digikey, $3.15 Paper Caps, Digikey, $24.28 Knobs, Bias Pot, IF Xformer Play Things of the Past, $31.35 Speaker Connector, NAPA, $2.96 Transistor, Quest Components, $32.50 Weld Nuts, McMaster-Carr, $2.00 TOTAL $132.04
Monday, December 2, 2013
Got the schematic today from Brian and started a little debug. I knew that the output transistor and the 12K5 tube driving the transistor was working so I started checking voltages at the detector stage. All looked good at the detector so I went to the last IF amplifier stage and found that the plate voltage was zero. Checked the voltage on the other end of the IF transformer primary winding and found 12 volts. It appeared that the primary winding was open so I removed the IF transformer and did find a broken wire. Not sure what happened to the transformer but it looks like the wire was eaten. There was about 1" missing. So I installed a jumper wire and found that the "sort of plastic" base was crumbling. I pulled out the epoxy and patched it up. Tomorrow I'll put the transformer guts back in it's case and reinstall it. Not the best of situations but that is sometimes the way it goes. The likeliness of finding a good replacement transformer is somewhere between nil and zero...
Here is the bottom of the chassis showing the bottom of the transformer
Transformer guts removed from it's case
Guts with the added jumper wire and a bunch of epoxy slathered all over the base.