Last year I bought a vintage game program called Plazma Line from www.suruga-ya.jp. I also ordered a Sanyo Cassette Data Recorder called MR33DR from Yahoo auction. According to the description the data recorder spins, but the seller could not confirm if it worked or not. Majority of the defective data recorder has some mechanical problems. If it spins, I thought it should be in good shape. The data recorder crossed the pacific ocean using the service from buyee.jp.
However, the data recorder didn't play sound. It spins. But no sound from the speaker and the phone jack. My problem became suddenly challenging then. But somehow I wrote a program that applies filters to the audio recording from a conventional audio cassette player and restored Plazma Line successfully.
Repairing my data recorder has been in my to-do list, but I have been postponing mainly because I didn't have a skill set to do so. Now, after making some serial connection adapters for FM-7, I thought maybe now I can do it. So I tried.
I was primarily suspecting the volume control. Since no sound comes out from the speaker and the phone jack, the trouble must be somewhere close to the magnet sensor before the lines branch to the two output ports. Variable resistor for volume control is a moving part and more likely to go bad compared to the static part. Actually my previous car, Nissan Sentra, once had a problem in the variable resistor that controls the air conditioning. It blew the air when I chose the max output, but no wind when I chose level 1 to 4. The problem was the variable resistor. It just didn't pass the current. The motor ran only when I chose max output, where the variable resistor was bi-passed all together.
I disassembled the data recorder with taking photos (so that I could re-assemble later).
By removing 3 screws on the back, I was able to open the cover. I needed to keep the lid of the cassette bay, or something was blocking. Recording-LED was tied with a screw on the front side of the cover, which I removed next.
Then the counter. I had to be careful not to damage the rubber band.
I wondered what this wire attached to the screw was. Turned out it was just bundling some cables.
Then the connector between the board and the mechanical module.
I couldn't immediately see a lever that could push this white switch. I don't know if it is used.
Finally I reached the soldering side of the board.
The variable resistor was sitting here.
I was able to remove the variable resistor.
If this part was the culprit, I could just order a replacement part, and that's it.
At maximum-volume position, 4.5 ohm between (2) and (3), 10k ohm between (1) and (2). At minimum-volume position, 4.5 ohm between (1) and (2), 10k ohm between (2) and (3). It's functioning fine :-(
So my hope was gone. I checked the wire connecting the magnet sensor head and the board. Everything looked fine. No cracks on the board. Capacitors looked just fine visually. If it was capacitor, I may hear some noise, but at least I should hear something. If there is a loose solder joint, it can be fixed by melting and re-solidifying the solder joints. So, I did it for all joints. Re-assembled, played, and still no sound.
At this time only possibility I can imagine is its magnet sensor head is gone bad. So, I hit the dead end. My data recorder is not functioning, for the time being.
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