Hello everyone, I have an Aiwa HS-G500 unit in excellent condition, but I’m facing a problem that I haven’t been able to track down. The unit goes into autostop immediately after pressing play, regardless of which side is engaged. I also own a J500, which shares the same mechanism. When I placed the G500 board into the J500 mechanism, the same problem occurred. However, the J500 board worked fine in the G500, which strongly suggests this is an electronic issue. I’ve already ruled out the rotation sensor, since the unit behaves correctly when the sensor is moved away from the board (it switches sides as expected). That’s not the case here. The problem is that it won’t stay in play mode, nor in rewind or fast-forward. If I keep pressing play continuously, then it does switch sides as it should, but as soon as I release the button, it goes straight into autostop. I checked several voltages on the logic IC and the transistors related to autostop, but didn’t find anything abnormal. I came across a post on Reddit describing exactly this issue, with a video included: https://www.reddit.com/r/cassetteculture/comments/1d1ym8o/troubleshooting_an_aiwa_hsg08/ Has anyone dealt with this before or can offer some guidance? Thanks in adv
First thing I would check is what happens at pin 4 of IC5. This should stay high (3V) and be pulled low (0V) briefly only when STOP is triggered. The buttons generate an analog voltage (through the resistor ladder) which is fed to IC6 comparator which generates the digital control singals that control IC5. The STOP signal can come either from IC6 or from Q20 (pulling pin7 of IC6 to ground). If this pin stays at 0V all the time, I would desolder Q20 to isolate the problem.
I just checked pin 4 of IC5; it provides a constant 3V. When I press play, it drops to 2.7V, and when I press stop, it goes to zero. I removed Q20 as you suggested, but there was no change. I had also tried removing Q16 and Q17, which seem to be related to the autostop activation, but there was no modification in the behavior.
I managed to fix the autostop! After thinking about that voltage drop from play to 2.7V, I started to suspect the capacitors involved. I had already replaced two of them, the 47µF and the 100µF electrolytics, but I hadn’t touched the 4.7µF tantalum. It seems the 47µF I had installed wasn’t a good fit—although it was new and had low ESR, its capacitance was higher than the others in my stock, around 70µF. Now I’ll continue with the repair and soon bring updates. Thank you, Valentin—after talking with you I arrived at this solution, which only reinforces the importance of sharing experiences here in the forum.
