After checking with the club president and thinking about this matter I realized that there might be certain liability issues, and will there be enough people to staff this service during the term of the hamfest.
Though I will offer my assistance in this idea I do have PRA responsibilities and I do want some time to enjoy the hamfest myself.
I also think we should limit the repair to simple testing unless the customer desires to open the rig himself and assumes full responsibility. We then could offer assistance at our discretion, and would charge for this service.
The most testing I have done when we were at Hosstraders was to see if the rig works with simple transmit, frequency checks, and receive tests. These tests normally didn't involve any opening of the rig.
Having a full operational repair facility may not what you want to offer as it could really open up a can of worms as the customer could blame us for the reason the piece of junk he bought didn't work. We will also have a good chance of not having the schematics or operational manuals and have to work "blind" on the equipment.
I would suggest that we set up an area for verification of rig operation (smoke test). and frequency checks (I have a counter). It would be manned by someone with electronics and amateur radio troubleshooting experience. The facility will have a power supply, Power meter, dummy loads, necessary cables, multimeters, and a rig to use as a test base (HF and VHF). I can furnish all the listed equipment.