I asked Stereo Fixers in Boca Raton and Music Technology in VA to "fix" the channel imbalance in my Luxman CL-32 pre-amp. They BOTH charged me a ton of money and "couldn't fix the problem."
When I had my shop, if we could NOT fix something, we charged the customer the $20.00 "look-at" fee and nothing else.
I guess times have changed with shops now charging lots of money for what they CAN NOT do.
If I took my car to a shop and they could not fix it, I would never pay them, nor would they charge me other than a minimum "look-at" fee in my experience.
Cheers!