Yamaha SPX-90
This Yamaha had already been in my workshop before. During the previous repair, I replaced the RAM backup battery and, while I was at it, the high-voltage capacitor, which had swollen and could have burst at any moment. This time, however, there was no audio signal at the output, and the cause turned out to be the missing -18 V negative supply voltage at the power supply output.
Once again, the culprit was another electrolytic capacitor that had shown no signs of failure during the previous service. This time it had also swollen and was heating up to a fairly high temperature, causing a short circuit to ground. This time I performed a complete PSU recap, restoring the effects processor to full working order. The power switch also had to be replaced because its shaft had become so brittle that it broke into two pieces during disassembly.
