Not sure if I can post about this mixer here as it’s really sort of Analog, but here goes, I was asked to look at a mixer the other day a Allen and Heath GS3000, he had done some routine service on it, part of this was to clean some of the switches on the input boards, since then he cannot switch out the PFL. MASTER PFL LED always lit on master board, so unable to hear L&R mix over control room speakers.
It seems that the switch cleaner he used has left a residue of cleaner which causes a high resistance tacking across the PFL switch, not anywhere near enough to bring on the input channel LED but enough to have the transistor logic switching see a PFL bus, as it will clear from time to time , but any use of a PFL switch locks it in again.
Has anybody else had this sort of phantom bus problem if so how did you fix it
Marconi 225
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