Toggle switch cleaning?

The Toggle Switches on the front panel of your DMC20 are totally sealed, no amount of whatever liquid you spray on them will ever get onto the contact surfaces. Toggle Switch as an example, there are literally 1000's of these in many different configurations.

The only thing you can do is to replace the switch, which appears to be somewhat easy if your tech savvy, if not take it to someone whom is. The switches appear to be mounted on a PCB rear-mounted to the faceplate using the switches as standoffs / mounting hardware.

Spectral DMC20 Internal picture

Best of luck

Peter

In studying the picture of the DMC20, I don't think the toggle switch has anything to do with your channel dropout issue. The switch on the front merely control relays that do the actual phase inversion of the output, so its my somewhat qualified guess that one of the relays, orange cubes located towards the rear of the PCB to the right behind the output terminals, or the two located in the center just behind these are at fault.

Best of Luck

Peter

Relays are readily available from for an example Mouser, Here is a suggestion, but need a little more information to find the correct type, which can be had from many different manufacturer of relays, which is a commodity. Although someone would like to think that they need to be infused with Audiophile Pixie Dust to sound "just right" :-)

Any reputable repair tech can procure a relay that would work, from suppliers like Mouser, Newark, Digikey etc. That where folks like Spectral and all the rest of us get them from.

Best of Luck

Peter

Yes indeed 😄 pop the cover on the DMC 20 and send me a photo closeup of the relays and I'll reciprocate with a link to a direct drop in replacement.

Good listening

Peter