Recently, when I was doing tape head alignment for my d3, the sound suddenly went out (motor runs just fine). Instead, I am hearing some static noise which gets louder in pause mode (the level is not affected by volume knob). I am not sure about the reason but touching and adjusting the head screw while playing did give some loud thumps before it died (I have replaced the last two capacitirs before headphone out from 220uf to ~560uf for more bass. That might be the reason for the thump). Replacing the last two capacitors doesn’t help either. No sound from the line out either.
The sound can sometimes come back if I touch the right place or hit the machine in the right way, but it is unstable and might be gone again the next day. I thought the head coils were damaged, but the fact that both channels always come back and go out at the same time rules out this possibility. Cleaning the record/playback switch inside doesn’t help. No sound in record mode either (normally I could use it as a headphone amp in record pause mode).
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I have tracked down what was wrong. It simply suffered from serious battery corrosion. This part is covered by a piece of plastic glued on the back of the circuit board, so it is not very obvious unless you remove the plastic. The solder lead had failed and I had a hard time removing the dead lead. On the top of that, the film conductor pads couldn’t stick to new lead properly. So I removed the film all together and replaced it with thin wires (they are covered by insulating material). They are a little too thick though (0.4mm), so I had to filed down the plastic cover a little bit.
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