James,
You should know to fan cool the CCD IC on the bottom when out of the case. These run hot. Use a good compound to help with heat transfer from the IC to the heatsink, like MX-4 compound. This statement about external cooling and compound may be redundant not knowing what you have done. Failure of the CCD IC will cause problems.
I have a 2440 and fully recapped it using high temp, low ESR and long life types. The battery was replaced with an axial type that is double the mA/hr of the original. Once working, recalibrating was easy. I wonder if you need more recapping and battery to see if it helps. The 22mfd axial types in a photo you posted, I used ULD 47mfd because I had them. The lack of a true ground may be a problem.
Mark
