I obtained a Luna-Pro F the other day, 'as is'.
A battery connector was destroyed, quite how the PO managed that, I don't know.
After fitting a new 9V connector and fly leads, I half-expected some results, but no.
It was quite intermittent, but at least there were signs of life.
I removed the back plate, removed the four long brass screws that hold the PCB in, then after careful inspection realised the PCB could lift out. What was still holding it in were the three tubular connectors inside that mate with three pins on the underside of the PCB.
I cleaned up the pins and tubes, gave a quick squirt of contact cleaner to the switches and put it back together.
Using a decent battery was able to get it registering something close to the L-P SBC I have, but I'll wait until I get a batch of fresh batteries to fine tune it.
So, looks like my ten dollar gamble might have paid off.
It looks almost unused, so that gave me some hope that problems were likely just old age and storage conditions may have just tarnished some contacts.
<edit to add>
Just fitted a fresh battery and the readings are within half a stop of the SBC, might tweak it a little bit, but might not.
The battery gauge pot definitely needs adjusted though - it shoots wildly off scale when tested.