[ho_co]

John--
I'm not sure, but I think the SL2 may have one meter battery and another for the VF meter illumination. That's probably wrong, and your friend has probably checked that anyway.

The camera was very 'traditional' in its day, which was certainly pre-LED, so I would guess filament bulb.

I'm not a DIY kind of guy, so my automatic answer would be to send it to Leica. They won't do just the bulb (or LED or whatever), but will clean and lubricate the whole camera. Therefore, the repair will not be cheap.

Not really OT: I was visiting a Leica dealer when a customer brought in a Leicaflex (SL or SL2, I don't recall) with some kind of problem. The dealer told the customer "Leica is too expensive, so let's send it to our local repairman."

The repairman picked it up about half an hour later and told the dealer it would probably run about $100. An hour later, the repairman called back to tell the dealer "I've never been inside a camera this complicated. I'm going to have to raise my estimate to $150."

If your friend feels comfortable exploring, I'd say go at it; but in the case in question, my feeling was that paying someone $150 to learn about my camera might have been excessive. (That was a number of years back, when the dollar had some value; I would guess the equivalent today would be about $600.)

My experience with cameras of that vintage is that the PX13 cells often corroded. The corrosion could be cleaned off the battery contact so it looked clean, but it wasn't unusual for the corrosion to have extended beyond that point internally. That's where I would start looking if there are two cells (which I'm now beginning to question).

Anyway, good luck!