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Topics - ryanckelso

#1
Hi All,

I'm new here, but need the internets help to fix my amp.

I've got a Yamaha G100 410 - Series 1. General Model with a DC board.

Everything works, tremolo, reverb etc however the volume is lower than it should be for a 100W amp.

I've done some initial scoping. But the problem alludes me.

When I turn off the amp, the volume first goes to nothing then surges and gets really loud! How loud it probably should be when its at full volume. Then it kind of fizzes out towards the end. Which sounds like a diodes clipping from a distortion pedal. So could be the electrolytic capacitors, discharging at the end? But why does it only get loud when its powering down?

Also another thing that confuses me is the 'Pre-Set Volume' knob does nothing to change the volume when turned. But I think that could be because its meant to be set by a footswitch, so you can boost when you want. A little clarity on that would be great.

I've got some basic knowledge and have built / fixed pedals before. But fixing this is the next step in the journey.

All help is appreciated.

Schematic Attached (hopefully)

Thanks!