I'm a speedotron guy, but nobody's piped in...
If the flash tubes pop in and out (vs. soldering like a Novatron) it should be easy to suss out your flash tube issue since you have a known working tube - you don't want to buy a tube and find the head is shot. NOS tubes do come up on eBay from time to time.
Since these packs don't have a symmetrical/assymetrical switch, you could verify it with a light meter and some quick tests (though you'd need two working heads). But it looks like the panel has the ratios printed by the cable jacks - I'd be surprised if the symmetrical pack has the ratios printed like that.
If your modeling lamp socket is the bayonet type, with 2 pins on the bottom of the lamp - that's a pretty common 250 watt model lamp. The 650 watt for 250v may require a lamp designed for 250v though - I'd make sure a softbox can handle that kind of heat.
You should be able to google up a way to check the trigger voltage with a multimeter (which you can find for like 5 bucks on line or at a harbor freight store). And google will tell you a lot about trigger voltages, safe levels, etc. The easiest way to get around this issue altogether is get a cheap radio slave (or a pricey one). Cowboy studio sells them for $30 or so - the 4-channel models have PC jacks on the receivers vs. only having a hot shoe.
You might contact a few repair centers with specific questions - some places have helpful folks who won't mind geeking out a bit, and you'll find a good resource for service.
Quality packs can last decades - I've got a speedo that must be 30+ years old. Regular use is good for their health! it's not a bad idea to have it looked at though, as the voltages involved are extreme.
Last edited by M Carter; 02-20-2013 at 02:59 PM. Click to view previous post history.