ChrisP2
Member
Lots of info around 60 Hz hum on these units when tone control enabled, particularly linked to the “Low” tone control. Had one on the bench, here’s what I found, hope it helps someone out there.
- Hum was audible and clearly visible on scope at over 10 mVpp primarly on Left channel
- Not volume sensitive, present with no inputs
- Poking around a bit noticed that factory tucked the blue wiring to CN-5 connector on the Tone board (from the Logic board) in between the caps on the Tone board. That wiring runs right past the power supply
- In this case moving that wiring up near the main harness helped significantly. Hum is still measurable at full Low boost but still significantly reduced.
- Pics attached.
- Hum was audible and clearly visible on scope at over 10 mVpp primarly on Left channel
- Not volume sensitive, present with no inputs
- Poking around a bit noticed that factory tucked the blue wiring to CN-5 connector on the Tone board (from the Logic board) in between the caps on the Tone board. That wiring runs right past the power supply
- In this case moving that wiring up near the main harness helped significantly. Hum is still measurable at full Low boost but still significantly reduced.
- Pics attached.
