The TR-610 sample I found at a flea market was not working, and upon examining the radio I noticed that the biggest problem was some wires torn from the antenna coil, so that when the radio was turned on from the loudspeaker only a faint rustle came out. The antenna coil on ferrite core is made of thin multi-strand wire and some wires had been torn right next to the winding.

With a lot of patience and using a sharp cutter I was able to free the short stumps of the broken wires from the layer of wax that covered the coil, so I was able to remove the paint that covered the stumps and weld them to the AWG 32 (0.2 mm) wire pieces taken out from an old transformer. I covered the welds with clear tape and stuck it to the body of the coil with melted wax from a candle.

Using an ohmmeter, I identified the ends of the windings of L1 and L1/a: the one with the lowest resistance was definitely L1/a. At this point I soldered the four wires to the radio circuit board by referencing diagram.

After setting up the ferrite antenna, there was a faint whistling noise coming from the speaker when tuning the radio, but this result encouraged me to continue. The next step was the calibration of the IF coil cores using an RF generator tuned to 455 kHz and a small plastic screwdriver, but after that I didn't get any improvement.

The action that proved successful was instead the replacement of all the electrolytic capacitors present in the radio. The TR-610 uses four electrolytic capacitors: one is 10 MF (C15) and is connected between the volume pot and the base of the first BF transistor, the others are: 10 MF C16, 20 MF C18 and C19 are all inserted together in the same casing.

To replace C15 with a new 10MF 20V Work component, it was sufficient to remove the volume and the tuning knobs to free the printed circuit and solder the new capacitor in place of the old one with R13 on the negative pole.

For the other three it was impossible to trace a similar multiple component, so I found in my magic drawer three small 22MF 20VW capacitors and joined them together with a bit of tape. The three new components fit perfectly into the space occupied by the old triple condenser. I welded together the three negative rheophores connecting them to a single wire that I welded to ground, the three positive rheophores I welded them in the respective pads of the printed circuit.

After this operation, when the radio was turned on and tuned to 936 kHz, the RAI-1 broadcast came out at full volume from the loudspeaker. The repair work was successful and the TR-610 specimen was honored to become part of my collection.

© IK3HIA, 2007