Thanks for posting those pictures Albert. It never occured to me that you could mount a linear PSU on top of the disc drive, I didn't realise there was enough room there. I regret that I've never owned an 800, and I only imagined squeezing in an FG Elektronics supply alongside the drive.

The 800/861 doesn't have much ventilation, and I'd be concerned about where the heat is going to go in that position. Some of them have holes in the internal lid, and some are plain. Which is this one? Rather than relying on convection, the chassis itself is a good heat sink, I found it can reduce the PSU transistor's temperatures significantly. I would try to mount the PSU on one of the chassis walls - maybe upside-down on the lid.

Do you know what type of PSU this is? 40W? 75W? Bigger PSU's are better able to run cool with a given electrical load.

Regards, Nick