Giesemann MH wont fire anymore

That's a tough one. I'm not an electrician, nor do I have experience with the inner workings of ballasts. Is there any way the fixture is still within warranty? If so, that would be my route. Beyond that, you'll have to wait for someone with more electrical experience (kcress or others...). Sorry I couldn't be of more help.

My guess is if it is a cap that blew it would be very easy to locate once you open the ballast.. if it is magnetic there really should only be 1 big cap in there and the top will be popped or it will be expanded like a balloon if it blew. You should still be able to read the specs on the side of the cap and be able to order a replacement. I know Hellolights.com sells replacement caps for ballasts. That is assuming it is a cap that went bad.. could be the igniter or the coil that went as well, depending on what type of ballast it is (electronic or magnetic). I only have experience opening magnetic ballasts myself.. if an electronic ballast goes out on me I just replace the ballast since I know nothing about the innards of those. I have seen a couple electronic ballast fixtures that had the capacitor outside of the ballast where it was easy to get to and replace.

EDIT: WARNING - Capacitors can hold a charge for over 24 hours after it is unplugged and can cause serious injury if it is charged and you use your body to discharge it. Always be extremely careful when playing with capacitors and it is a good idea to keep it unplugged for 24 hours prior to working on it if at all possible. If the cap is blown though obviously it won't hold a charge. I watched my dad get thrown through a sliding glass door when I was a little kid when he was working on an old TV and touched a capacitor with the screwdriver.. luckily the worst injury he sustained was to his ego but it could have been much worse.