Regular alkaline batteries should always be 1.5 volts, the rechargeables (NiCad, NiMH) are 1.2. If the flash has sat unused a long time (years) the main capacitor may have degraded and need "re-forming." Unfortunately, if it is seriously degraded it may put enough load on the charging circuit that the charging won't start up, and thus it can't reform the capacitor. That is why folks recommend putting batteries in an unused flash and running it for ten or fifteen minutes two or three times a year.
I would try harder to clean up the contacts first, that may be the problem; but it may not. I have two quite ancient electronic flashes, one inherited, that have perfect battery contacts but won't start. I suppose a serious electronics tinkerer (like I used to consider myself) could try to get inside and isolate and slowly build up charge on the capacitor with a lab power supply and possibly recover it. Although if I went that far I might try and find a replacement capacitor (which may not be easy). Note that the internals of such flashes use several hundred volts and are not to be trifled with, lest you have an illuminating experience of the wrong sort.
Edit: According to a manual I found online, it will run on NiCad batteries; fewer flashes but faster recycle than with regular AA cells. They also recommend running it once a month to keep the capacitor formed. That sounds a bit excessive to me, but other than eating batteries doesn't hurt anything I suppose.
Last edited by DWThomas; 01-07-2013 at 10:33 PM. Click to view previous post history.