LazarusNine said:

I was the winning (and sole) bidder on a Power Macintosh 7100/AV with monitor, mouse and keyboard for £25 + £10 delivery. The machine looks lightly used and the seller (an original owner) claims that it was not heavily used even when first purchased. The first thing I'll do when it arrives is get that PRAM battery out of there post haste! I'll glance at the capacitors, though I imagine the 7100 won't be high on my recap list, as I still have an LC III to get done (among others). Anyway, thanks for allowing me to share. I'll post pics when it arrives.

Click to expand...

The most common failure I"ve seen in PM7100s is for the heat sink grease to turn to powder and then the machine overheats after a few minutes of operation. 

The results can be very frustrating, as the failure manifests like a corrupt OS install.  So one reinstalls the OS, only that may or may not finish because of the overheating time.  Etc.   The time I was cursed with this, I only figured it out because once, I got screen artifacts of a type which I had seen before from overheating PPC601s. 

Anyway, while you're changing that PRAM battery, pull the heat sink, clean off the old grease (powder residue, unless someone else already refreshed it) and apply new heat sink grease.   Be careful not to apply pressure to the CPU, they're prone to cracking, and do not over-apply the replacement grease, nor get any on the pins of the CPU.   I killed a PPC601 that way once, by getting heat sink grease all over the pins.  Sigh.