| Overview | Replacement Parts | Re-Capping | Troubleshooting | Conclusion |
|---|---|---|---|---|
The Heathkit FM-3 / FM-3A is a 7-tube FM tuner that measures 12 9/16 x 3 5/8 x 5 7/8 inches. There are two RCA outputs on the back, one a high-level output for use when the audio level is desired to be controlled at the tuner or if the amplifier used with the tuner has low gain. This output (closest to the antenna terminals if assembled correctly) should be used if the tuner is being plugged into the phono jack of a TV or TRANSFORMER-type AM radio.
My FM-3A tuner was sold as "Non-Working," so I assumed it would be an easy re-cap job to get the radio playing again. Before I turned it on and did any testing, I took the tuner apart to clean and re-cap the chassis. I discovered that the majority of the brown ~22 A.W.G. wires had crumbling insulation, so I replaced those.
| Original Rating/Part | New Part Quantity | New Replacement | ||
|---|---|---|---|---|
| 20/20 MFD. @ 350V | 2 | Sprague TVA-1608 | ||
| 10 MFD. @ 50V | 1 | Sprague TVA-1304, Sprague TVA-1504 | ||
| 20 MFD. @ 250V (FM-3A ONLY) | 1 | Sprague TVA-1508 | ||
| 2 MFD. @ 150V (FM-3 ONLY) | 1 | Sprague TE-1501, | ||
| .05 MFD. @ 400V | 2 | Mallory C-MD047-630**, Generic C-TD0047-630** | ||
| Output Transformer | 1 | Hammond P-T125ASE** (Untested), Merit A-2998 (Out of Production - Click for Specs) | ||
The re-cap was kind of difficult because of the small chassis size, so I wouldn't recommend this as a starter radio (I would recommend a General Electric 514, 542, or 543). However I did manage to fit everything in.
DOCUMENTATION: Riders Schematic, Jewel 920 Sam's Photofact
The radio still wouldn't play after the re-cap, so I checked the tubes, volume potentiometer, and the output transformer. From there, I found that the primary of the output transformer was open (it should be 170 ohms using a VOM/VTVM), so I ordered a N.O.S. Merit A-2998 transformer (the one specified in the service manual). After replacing the output transformer, the radio played and got pretty good reception.
This was the first ever radio I repaired and I'm glad that some of my amateur mistakes didn't harm anything. I guess it goes to show that these radios were and are durable.