I picked up an Aerco pre here in the Yard Sale section. It worked well for a while, now I am getting some noise from it and would very much appreciate some advice.
I'm powering the Aerco off a Tekkeon external lithium battery, and I noticed a "whine" in the signal. I'd been running the Tekkeon at 9v, so I raised the battery voltage to the next few steps up in voltage. When i raise the voltage, the "whine" turns into "chirping".
I tried a second charged battery and got the same results. I moved the mics to my other Aerco which runs off 9 volts, it not only had no whine in the signal but a much hotter signal overall. I know there are a few different gain ranges for the Aerco, so that might account for the gain difference. Are there internal gain settings I can change myself or does this require a trip back to Jerry?
I'm certain that I've isolated the noise to the Aerco pre. What troubleshooting steps might I take before shipping it off for repair?
Thanks in advance,