Firing Ushio Using Tar Ballast

[Delphinus]

It should be the right combo, Ushio's are pulse-start.

You're sure it's a pulse start ballast? It sounds like you're using a probe start and not a pulse start. There should be three components, the transformer, the capacitor and an ignitor (looks like another capacitor, but is different). If only two then it's a probe start (or you're missing a component ).

I use probe starts to fire my Ushios (that's just what I have, and have never bothered buying new ballasts). I find they are fussy to start for a few weeks at first (but they do eventually fire on their own, it might just take 5-20 minutes). Swapping the leads sometimes helps. Also check all your connections and make sure they're really really solid. Eventually the bulbs sort of burn in and fire up OK.

Going for hours though, without starting, then something's not right.

Can you get into the socket and bend the centre contact out a bit (so that it presses harder into the lamp threads)?

What about the nipple orientation? I hear varied opinions on whether this matters or not, but maybe make sure that it's pointing upwards. Reorientate the socket if you need to.

HTH ..