Interesting 2 issues I am working on a PS-2 board set. First is a processor that kicks out in reverse only and conventional only. The other was a Power Supply that needed to be refurbished. Once I did the normal power supply fixes I still could not get shutdown sounds with the battery. So I put a BCR on to see if the charging circuit was working. It was and it charged the BCR up to 5V. When I powered down, I had shutdown sounds. This led me to investigate the charging circuit closer. Turns out that one of the power trenches sole purpose is to operate the boost circuit and charge the inductor. After further investigation I realized the PT wasn't working and when the power is removed the battery voltage is the only source and the processor shuts down since the 2.5V boost of the inductor is not there.
With a BCR installed you have 5V available and the BCR can sustain the shutdown sounds. I wound up removing the PT and the board still functions fine with a BCR, confirming it's only purpose is charging the inductor.
Turns out the processor I was using to test the Power Supply also did not kick out in reverse when BCR is installed. I imagine the added starting 5V of the BCR can help keep the 5V circuit high despite the extra load of being in reverse.
So for these types of faults a BCR can allow a defective board to work, when a battery won't. I am still trying to run down the cause for the processor failure in reverse. The main difference is the 5V relay is held energized in reverse. Reducing volume or turning smoke off (2 high 5V drains) can delay or prevent the kick out. Hoping something simple like a fet or buffer. G
