dimesav said:
Squarewave - I tried to get a reading between the earthpin on the power connector and the chassis, hope I'm not being dense but did this while the console was off! Couldn't get into the connection with the plug in as its all insulated up at the innards. Have a hunch you meant to test while powered up? Anyway.. got a reading of 2ohms from certain points of the chassis, nothing from others.
Resistance measurements must be done with the power off. Otherwise, even small currents can throw off the meter.
In theory, if all of the connections in and out are balanced, connecting the chassis to earth should not impact performance. It is primarily for safety. Perhaps there is something special going on because it can also run on battery. If you don't plan on using battery, you might try to properly earth ground it. If resistance between earth pin and chassis is 2 ohms (not clear that's what you did from your description), that is too much. It should be near zero. Note however that it can be difficult to get your probe tips to get through plating and anodization. So you might start by just testing chassis to chassis until you get a proper zero reading. Also sanity check what "zero" is by connecting probes together. Then, after you've found a good spot on the chassis, check the earth pin again. If it's not zero, you should divide and conquer that and figure out why.
dimesav said:
Also, tapping on it with something plastic/wooden still caused the noise, and the problem seems to be before the master fader as is silent when pulled down.
First, my last comment was wr-wr-wrong when I said it would not be upstream if the master down cut out the noise. If the noise goes away when the master is all the way down, then the issue is in the master or
upstream. So still divide and conquer but upstream.
dimesav said:
A final question, the manual states the mixer doesn't have to be earthed as well insulated, is it worth running the external earth on the rear of the mixer to anything to test?
Again, I actually don't think that's the main problem. It might be an issue. It sort of sounds like maybe something is actually causing the chassis to develop a voltage that gets discharged when you touch it. But that would be a separate issue.
I would say just keep doing what your doing. Try to pull out as much as you can (can channels be removed?) to reduce the possiblities and then just keep trying to narrow it down. It sounds like it's in the buss or master or connectors like you said. If you narrow it down that far, you could just try to connect the meter hands-free as described before and see if the resistance jumps when you tap or press on the backplane. If yes, then it's a simple matter of narrowing the test points incrementally until you find the bad connector or whatever it is.
Definitely could be a bad solder joint like radardoug says. Solder joints can crack and loose contact. They look fine from a distance but there's actually a crack and the two parts are just touching. After a short time (sometimes within minutes) oxides build up and it starts to loose connection. But it is also very possible it could be a bad connector or a burned up resistor of half-a-dozen other things.
Just keep going. Great learning experience. And it's a v. cool peice of gear. I don't own a mixer but I would like that one because it's got bantam jacks on the back and I'm a patchbay / bantam jack fan.
