Eagle:
HO sockets (sign type) are notorious around here for corrosion. A 'bad' contact between the socket contacts and the bulb can be a real pain. Next on the 'list' is socket spring tension. Then, secondary wiring failure; usually in the 'raceways' behind the sockets, where ya can't see it until you take ita all apart.
We have a few that use F120 HO (10' bulb), one ballast, 4 bulbs; one lamp out, all are out. Sure wish the mfg did the "one out; balance lit" thing for HO sign ballasts.
Signs can be a real "PAIN" or a "good gain"
PS; The secondary voltage should be printed on the ballast label.
Good Luck
John
