We have a number of Gallien-Kruger's Fusion 550 Bass Amp heads in our rental inventory. Interesting amp, though I'm still somewhat puzzled by the motorized pots in the front panel preamp assembly. I had one earlier in the year with substantial Turn-On/Turn-off Switching transients, which were again from the Preamp board. I got replacement preamp board to cure that. Now I have another, which also has the 'nice' benefit of a Master Volume pot that can generate Rail to Rail transients by merely rotating the Master Volume pot in the first 120 deg arc from full CCW. I pulled the PCB assembly out to see if it was something I could pull apart, but....these aren't built for disassembly like other simple single-gang pots are.
Unplug the tiny Woofer and Tweeter connectors on the top side of the Preamp PCB assembly's interface harness to the power amp, and the turn-on/off transients are gone. After seeing the pot 'noise', I think I'll take the easy way out, rather than mess with trouble-shooting that preamp board and removing that motorized dual-gang pot. Another adventure in Lead-Free solder, double-sided PCB with tiny-tiny solder pads. Life it too short to mess with those.
Unplug the tiny Woofer and Tweeter connectors on the top side of the Preamp PCB assembly's interface harness to the power amp, and the turn-on/off transients are gone. After seeing the pot 'noise', I think I'll take the easy way out, rather than mess with trouble-shooting that preamp board and removing that motorized dual-gang pot. Another adventure in Lead-Free solder, double-sided PCB with tiny-tiny solder pads. Life it too short to mess with those.
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