Prior to the amp shutting down issue , there was a constant low level hum for several months along with loud pop's when turning the amp on and off. Given that the Power Supply Filter Capacitors are over 20 years old, I pulled them out of circuit and found that one would not hold a VDC test charge using a 9VDC Transistor Battery. One read 8.65VDC and the other one 0.004VDC. They are 4700 MFD @50VDC 105C. The fuse didn't blow (it's 4amp SB) and there is no indication of anywhere on the board of excessive current or overvoltage, i.e., no scorch/burn/component bulging. One interesting thing is that the Chorus LED remained ON with power switch in the OFF position but 120VAC power still being applied to the amp. Looking at a schematic the Chorus LED gets its feed from the power supply +/- 16VDC which is taken downstream from the subject filter capacitors. The other feed is +/- 40VDC to other components on the chassis (please note this is a Solid State Amp). I have ordered 2 replacements which I feel will correct the hum issue being experienced and has a good chance of fixing the shutdown issue as well. With one capacitor not holding a charge and both being well over their service life; I feel that on power-on the DC voltages (especially the +/- 40 VDC) is unstable resulting in the amp shutting down. Any input on the above would be most appreciated. If there are further troubleshooting steps that should be done, please pass them along. Of special interest would be hearing from anyone who has experienced the same issue and how it was resolved. Thanks!