I have an MXR 114 10-band stereo graphic equalizer hooked up to my receiver's pre-amp. I have noticed that the right channel "level" controller has some kind of offset (that occurs on irregular intervals) that causes the right output volume to be a little lower than the left, when both are set to output at the same volume.
Then, a few weeks ago, I noticed a moderate volume of hissing in the left channel, and VERY loud hissing in the right channel. Naturally when troubleshooting, I disconnected the equalizer and short-circuited the preamp to see if the equalizer was the problem. Sure enough, it was, and the hissing went away.
With no input going into the equalizer, I simply hooked the output of the equalizer to the input, and the hiss was still there. Obviously the hiss is coming somewhere after the input. Adjusting the "level" controls on the equalizer did not affect the volume of the hiss. However, when adjusting the individual frequency band levels, the hiss increased in volume at each respective frequency I was raising the level of.
It seems to me that the problem is occuring somewhere in the circuit between the "level" controller and the individual frequency band controllers. I opened up the equalizer and tried cleaning it with some electrical cleaner - that only seemed to make the problem worse. There seemed to be some kind of black corrosion on the op-amp leads. At first I thought they were burn marks, but I could have been mistaken. It didn't smell funny or anything and the voltage regulators on both channels had that same "corrosion" on it. I tried disconnecting the main ground to see if there was a bad ground somewhere, but that wasn't the problem either.
Anybody have any ideas? Bad caps?
Then, a few weeks ago, I noticed a moderate volume of hissing in the left channel, and VERY loud hissing in the right channel. Naturally when troubleshooting, I disconnected the equalizer and short-circuited the preamp to see if the equalizer was the problem. Sure enough, it was, and the hissing went away.
With no input going into the equalizer, I simply hooked the output of the equalizer to the input, and the hiss was still there. Obviously the hiss is coming somewhere after the input. Adjusting the "level" controls on the equalizer did not affect the volume of the hiss. However, when adjusting the individual frequency band levels, the hiss increased in volume at each respective frequency I was raising the level of.
It seems to me that the problem is occuring somewhere in the circuit between the "level" controller and the individual frequency band controllers. I opened up the equalizer and tried cleaning it with some electrical cleaner - that only seemed to make the problem worse. There seemed to be some kind of black corrosion on the op-amp leads. At first I thought they were burn marks, but I could have been mistaken. It didn't smell funny or anything and the voltage regulators on both channels had that same "corrosion" on it. I tried disconnecting the main ground to see if there was a bad ground somewhere, but that wasn't the problem either.
Anybody have any ideas? Bad caps?
