issues with my system 8 24x8....

[RedFroDevil]

howdy folks...


so yeah, I have a system 8 console manufactured by allen & heath, and had it serviced about a year ago...

I've begun to notice a very odd characteristic about the mixer--whenever i route anything through buses 1 thru 8, i start to hear increasing amounts of 60hz hum.... its most audible when i have the levels turned up on all of the busses and main outs... i have cheked EVERYTHING (to the point of unplugging anything lined-in to the mixer) and have determined it to be the mixer itself... even if all of the channels are turned all of the way down, it seems that when i make the actual connection between a channel and a bus from within the console (via the routing buttons), i get a low signal of hum (plus the usual very low level of hiss)....

i guess im looking for a diagnosis and a possible cure... getting it serviced again is an option, of course, but i just want to make sure there is nothing im missing before i go that route, because im going to have to drive it to nashville from columbus, oh, to take it to a properly qualified tech who can work with the "star ground" configuration on alot of these british boards, and thats money and time that i dont really have atm...

any help would be appreciated.

thanks.

 

[xstatic]

So the hum only happens when you buss channels? Or is there constantyl and just gets worse as you run more signal (turn up the buss faders while routed to the mains)? Is it plugged into a different AC circuit than the rest of your equipment? Are you also using a computer? You may try an AC ground lift adapter temporarily to see if lifting the AC ground helps. If it does, than some AC grounding work will need to be done.

 

[RedFroDevil]

So the hum only happens when you buss channels? Or is there constantyl and just gets worse as you run more signal (turn up the buss faders while routed to the mains)? Is it plugged into a different AC circuit than the rest of your equipment? Are you also using a computer? You may try an AC ground lift adapter temporarily to see if lifting the AC ground helps. If it does, than some AC grounding work will need to be done.

yes, the hum only happens when channels are bussed... there is not any hum at all when nothing is routed... the ac circuit question is rather irrelevant--i unplugged EVERYTHING from the mixer, and it still happens when i bus channels... i am using 4 different computers, but none of them are hooked up to the mixer itself... I will try the AC ground lift adapter trick, but I'm pretty sure its not going to do any good--the only time there is hum is when i route channels through the busses, period, bottom line. that would rule out that the problem is the AC ground, and that it more than likely will be within the mixer...

thanks for shooting the "general ground-loop questions" my way, though--its always good to have someone to put the proceedure in front of me to double check