Yamaha M1516, M1532 owners: Noisy master section?

[FlowersForHuman]

I have a Yamaha M1516 (purchased through TOMB!) that is really great...amazingly quiet, warm pre's, etc...only the master (program out) section has tons of 60hz hum. The summing sounds fantastic compared to my DAW but the hum renders my mixes pretty much useless. Id be so happy otherwise!

Before I rip my whole setup apart I figured I'd check to see if this is a common issue or if anyone has any advice...this is where my knowledge regarding power supplies, etc falls off. I've tried different outlets, unplugging/disengaging everything, new cables, and everything else I can think of...I just can't seem to get rid of the hum. I can even hear that hum change when the power in the house shifts. It sucks!

Any smart people have advice?

Thanks!

-Harold

[digitaldrummer]

the master outputs say they are "phone jacks" which could mean they are unbalanced? I don't have the schematic but if you do you can check. what happens if you use the program (PGM) or matrix outputs (which are XLR and balanced) - any better results?

Mike

[FlowersForHuman]

Full manual with schematics here:

http://www.impressplay.com/webspace/doc ... manual.pdf

http://www.impressplay.com/webspace/docs/M1532E.pdf

The M1516 is of the same design as the larger units of the series.

Not sure where you got the phone jack info, but the connections I've been using are balanced XLR (to TRS input to my converters). At first I had them wired XLR to unbalanced TS but I switched to the balanced cables with the exact same results.

I also tried routing the program sends to the matrix mixer and using the matrix outs via balanced cables. Exact same result.

I'm thinking I may have a ground loop somewhere or perhaps something is wrong with the power supply or master section. The mic/line input channels and effects send busses are all dead silent (which is why I love this board), and I only get the hum when tracks are summed to the program out master bus.

Also, each of the 4 program out busses gives the exact same level of hum.

Thanks for the reply!

[digitaldrummer]

yeah, I was looking at the manual too and it mentioned "phone jacks".

you might try disconnecting the shield on one side of your XLR/TRS cables, that way it should avoid a ground loop if there is one. The shield will still be grounded from the other side.

otherwise, if you haven't recapped any of the modules, then that's probably where I'd start. Swap the electrolytics in the power supply and maybe the master modules first. these consoles are at least 25-30 years old now (I think?) and electrolytic caps can dry up in that time.

Mike