GGG mini mixer, all of the sudden, crazy radio noise

[sjaltenb]

I have had a GGG mini mixer in my system for about a year now (large multi FX board)

it mixes the original analog signal with a few outboard delay units. It has always worked great, sometimes if i didnt have anything plugged in one of the delays but had the volume on i'd get a slight noise. Anyway, I haven't worked on the board in quite some time but opened it up today to do some modifications.

I didn't do anything strange involving the mixer, or anything close. but I closed it back up, cranked it up and found the mixer to be horribly noisey! radio interferance, crazy squeals that swell up and down, and change when i turn the mixer on either input (there are 2 adjustable inputs and one direct w/o a pot- the dry signal)

Well i opened it back up and figured it was a cranky ground, but it doesn't seem to be a ground issue. I also changed out the opamp with a few I had on hand, same problem.

Any ideas?? If it had not have worked perfectly for a year i would say its cause outside radio interference, but that shouldn't be an issue in this case. I know that all the signals going into the mixer are perfectly clean because I was able to tap into each and have a listen.

Thanks!!

[sjaltenb]

as a side note i just accidentally realized.......it works without an opamp?!?! although its a little quiet...??

[lazerphea]

Maybe you accidentally moved some component and it now touches the back of the pedal? 

[sjaltenb]

I tried moving everything around, checked all connections, etc.

I think I may have stumbled upon something more serious than I previously thought. The Mixer is the ONLY thing introducing noise into the rig (all effects aside, just straight signal through the board). If i monitor the dry signal, I can dime my amp on all controls and get nothing but guitar. As soon as I switch it over to the mixer (even with the delays (the other 3 inputs) set at Zero, I get a lot of white and squealing noise. This is with the External Delay disconnected. The delay is a TC Electronic D-Two, and I have monitored the output directly to the amp. It introduces a tad of noise, but only if the amp is up to around 8.

One odd thing is that sometimes when I power up, I won't get any noise, no matter the settings, until I change them. Upon changing the mix, the noise comes back and does not leave until I power off.

Very strange, but I think I may have to re-design this part of my rig in order to perfect the lack of noise. For those not familiar, this is the rig:





Thanks!

[sjaltenb]

Ignore all of the above.

the problem is with the GeoFX A/B/Y Splitter. Although I was probing the output of the mixer, the A/B/Y was sending noise back through it's input. I removed the Splitter and the problem is solved (with the Mixer anyway).

I am guessing the noise is coming from the MAX1044 charge pump or one of the opamps are bad. I know i had one in backwards...

I have searched around and seen a few things...one being that I should connect pin 1 to 8? Is that correct?

Thanks. The board is now almost completely silent, except for a tiny hum at 60% power on a 50Watt amp...audible within maybe 20ft of the amp. I am in search of completely silence, however, and this one has me miffed!