Bill Cornett , Apr 01, 2004; 10:59 p.m.
Ken-- I am assuming that the battery you are using has also been in storage for ten years, but you don't say. Working on that assumption, I've known rechargeables to go dead in a year, and over ten years with no maintenence is something that very few batteries can stand. Personally, I'd switch to sealed lead-acid batteries. You can pick them up at any good electronics store. The ones that put out 6 volts as opposed to 6.5 won't denude the flash unit's performance much, as the original battery pack probably went down to that level after a few flashes anyway. You will most likely be able to fit a single sealed LA battery in the place of the cell pack.
I can see a good, fully-charged battery going down to about four volts under a massive drain, but not 0.6 volts, as your post states and assuming that wasn't a typo. Typically I see my batteries going down to 4.5 volts for a fraction of a second after a flash goes off, if I'm running say, two Vivitar 285's off of one 1.5 amp-hour battery. If I'm using a 12 amp-hour cell, then the needle barely drops even with two 285's on it. 0.6 volts isn't going to charge anything.
A couple of questions-- One, if the battery is new, is it getting hot when it is trying to recharge the caps? If not, then there is something wrong with the battery. It would take a very low impedence short circuit to pull the voltage down that low, and in that case, something should be smoking, either the power cables or the caps or the circuitry inside the flash. The fact that it still whines probably means that the charging circuitry, including the voltage doubler, is still OK, and that means that the current draw shouldn't be too massive. I'd put my money on a bad battery.
Now, there is a chance that it could be both the battery and the capacitor, but you can spend $15 for a new battery and see how much good that does before shelling out for the cap.
Best of luck, and be careful. -Bill C.