Repair Stories

Sony TCM-131 Cassette Recorder
by Mike H. - a partial success.

All photos ©2023- Rushmoor Repair Cafe
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Job #190 was this little Sony TCM-131 cassette player which arrived at our March session, it had apparently been bought from a well known on-line auction site as a - fully working Walkman - unit, which it obviously was not, nothing moved, no sound, new batteries had been fitted but the terminals were heavily corroded and needed cleaning. We stripped it down and found that mechanically it did seem to operate from all of the buttons, the motor started but the drive belt was stretched, there was no sound and the FF/FR functions didn't work although the buttons did latch in place.
1) PCB marked up for disassembly.	2) Split on idler wheel.	3) FF/FR actuator 1st part.	4) FF/FR actuator 2nd link.
After marking the PCB wiring points (1) so they could be unsoldered and the board removed it get to the mechanics, further investigation revealed several common mechanical faults that we see on a regular basis with cassette players, tape recorders and videos - broken, slack or "gooey" belts, and plastic stress fractures especially where springs or press fit shafts (2) are involved, worryingly a loose small opaque plastic part was found inside the housing.
In this case the FF/FR 2nd link (5-6) had snapped in two and this was the tiny mystery part found in the case. Made from what appears to be a self lubricating plastic, age stress from the return spring had caused the end to split off so it does not engage the FF/FR 1st part. We did clean it and try reassembly with several differing adhesives but with no luck, the spring would probably have snapped it off again anyway. Sometimes spares are available on‑line but unfortunately not for this unit.

5) Broken FF/FR 2nd link.

6) Broken FF/FR assembly

7) Partially assembled and working.

With the unit in pieces we fitted a new drive belt to restore tension on the drive, resoldered the PCB connections and reassembled the mechanics, it now appeared to play but still no sound at any volume setting, and the FF/FR was never going to operate correctly anyway.

Then we had a light bulb moment !. When first examining the unit with the owner we had noticed the power LED appeared to be intermittent but we had assumed that there was a suspect contact somewhere, that's what it looked like at the time anyway. We should have cottoned on to the fact that the random indication was a recording level, especially as the LED was labelled "REC/BAT, doh, and the "intermittency" changed with handling the device, but why might it be recording when it's supposed to be playing ?.

Solution - there was yet another pesky bit of mechanics under the PCB that engages with a tiny slide switch, that mechanics had somehow come out of alignment with the switch, never changing its position, so it was constantly recording. Realignment of the switch brought back the PLAY function, we have sound - Yay !, indeed we found that the test tape we had used for diagnosing cassette decks has now got our discussion with the owner about its possible problems, it had been recording all along !.

You can see the repaired but partially assembled unit playing our test tape in a short video on the right (7), hover over the image and click the play button. [Back to the top]

Close window - Sony TCM-131.