Vintage Synth Repair

>>on 3 occasions, i have had to pull the PSU and replace parts. its a +15/-15/+5 PSU...... there are multiple outputs for each of the  voltages/ground......wire all of the grounds/voltages together to their respective pins, and solder to the male harness connector of the old psu?<<

just my 2c, & I don't claim to know the polymoog, but-

are you sure all those individual connections are from common supplies? you may find you end up with digital noise all over analogue audio circuits, or other funnies like that. first, get a schematic & check. but it does sound like the same trick as you see in PCs, where a single multi-output supply uses several conductors to get to the motherboard in order to increase the current capacity of the cabling without resorting to stiffer large diameters; these would be harder to install & would be impossible to fit with hf suppression devices.

but other than that, so long as the current requirements are met & the character of the synth isn't going to be affected by a "harder" or "softer" supply (there was some correspondence about this a while back in the context of a sick arp 2600), then it's probably a good idea & one less thing to worry about while you coax the rest of the thing back into reasonable health.
certainly, refurbing or removing the worn PSU contacts (& consider hardwiring if it's practical) will improve things, as anyone with a LAMM memorymoog will attest.

duncan.