I got a Variax 700 some years ago, and the whole time it's had this cold/weak A string issue. It'll occasionally be WAY quieter than the other strings. Usually doing a big pop on the string (pulling it away from the body and releasing) will reset it. I only use the VDI, so I don't know exactly where it's happening since I haven't been able to check on 1/4" (the intermittence also doesn't help). Any ideas if there's a solder point I could check? Might it be something on the 1/4"/VDI jack? Any ideas would be helpful. TYIA