I have a SPA500 powering a CSS 12" sub. Hanging the plate amp off the back of the sub enclosure. Built this sub back in 2016, has worked great until I moved it from my work office to my home office. It got jostled around quite a bit moving it down my stairs and when I plugged it in immediately this loud buzzing I associate with mains (60Hz) comes through the woofer. After checking all the wires and changing power sources I gave up but came back to it later and it was dead silent. Turns out after awhile it sorts itself out and as long as I didn't unplug the amp it was fine. Ie. waking up from auto power off wouldn't result in the buzz/hum.
However, now a few weeks later it's making a slight buzz when coming out of auto off that isn't as loud as when it's from pull power disconnect state but it also doesn't fully go away anymore. I assume whatever the issue is, is getting worse.
Anyone have any advice they can share of how I can troubleshoot which component(s) I need to replace? The amp appears to work fine otherwise and the price on these amps has skyrocketed since I last purchased so I would like to try a repair myself. I am fully capable of using electronics diagnostic equipment though I do not have an oscilloscope. I've built and repair several electronic kits and devices in the past I have no issues doing solder rework on a device like this. I just don't know much about analog amp design or diagnostics.
However, now a few weeks later it's making a slight buzz when coming out of auto off that isn't as loud as when it's from pull power disconnect state but it also doesn't fully go away anymore. I assume whatever the issue is, is getting worse.
Anyone have any advice they can share of how I can troubleshoot which component(s) I need to replace? The amp appears to work fine otherwise and the price on these amps has skyrocketed since I last purchased so I would like to try a repair myself. I am fully capable of using electronics diagnostic equipment though I do not have an oscilloscope. I've built and repair several electronic kits and devices in the past I have no issues doing solder rework on a device like this. I just don't know much about analog amp design or diagnostics.
Without a service manual or schematic, it's tough to do component-level troubleshooting. But your narrative and symptoms suggest an intermittent connection/solder joint. Rising operating temperature might appear to cure an intermittent connection.
If you disconnect sources, is hum still present? Can you provoke hum by wiggling input connections? Any susceptibility to thumping/bumping?
Open case and prod with wooden chopstick or similar while listening. Stay safe! Devote particular attention to supply section, heavy components that would be sensitive to moving impacts, connections to jacks, wiring connection at board edges, etc.
Good luck!
If you disconnect sources, is hum still present? Can you provoke hum by wiggling input connections? Any susceptibility to thumping/bumping?
Open case and prod with wooden chopstick or similar while listening. Stay safe! Devote particular attention to supply section, heavy components that would be sensitive to moving impacts, connections to jacks, wiring connection at board edges, etc.
Good luck!
Yes, and I even moved the sub to a different room and connected to a different circuit to rule out anything environmental. No interaction with anything external of the amp changes the hum.
Temperature is an interesting thought. It was warmer in my work office than at home and the past week the a/c has been running more due to it being hot outside making my home office colder than normal.
I'll rig it up so I can have it connected to the woofer still while having the internals accessible.
