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high pitched noise coming from Apple II Plus power supply
Posted by: habibrobert on 2023-09-22 22:16:22 I was gifted a Apple II Plus, it was untested by the person who gave it to me. I took the power supply out and measured the voltages which were consistent with the values written on power supply specs. I then decided to connect it to the mother board and turn it on. As soon as I did I noticed a high pitched (could even be described as clicking) sound once the power supply was connected to the motherboard. The motherboard did not power on, no beep, nothing. Has anyone experienced this before? Would it be reasonable to assume that the caps have gone bad and cannot produce the correct voltage when connected to the board? Or is there something wrong with the board? I'm really hoping its the power supply and not the board! I'd appreciate any advice.
Posted by: Byrd on 2023-09-23 00:28:32 Yes, assume capacitors (also replace paper filter caps), you also need to test voltages on these with the unit under load
Posted by: bibilit on 2023-09-23 04:26:38 Apple II PSUs are pretty reliable, except for the RIFA problem. According to your issue, i will rather have a look at the logic board. Next to the PSU connector you will find several capacitors (black bullet shape ones) have a look for any shorted one. Pretty easy, using a multimeter, check for continuity.
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