Hi. Here is something I found a couple of months ago on a Zenith DLP set. I don't remember the model number but it probably covers many of them.
This set came in doing little of nothing. Another shop had sold him a light bulb but that didn't help as old one was good. Okay, I check some things. Bulb good. I check voltage to ballast, about 170 when off, 390 when turned on. Good there. I call Zenith for some input. Zenith says 'replace the ballast'. Okay, I replace ballast because they say they have had problems with them. Same one fits Samsungs, some Sonys, etc.
Nothing.....well poo. Okay, new ballast from me and new bulb from other shop. Lets look further. I slide whole light group out for a closer look. I look for fuses or other blown parts. Well, right underneath a big bundle of cables, well hidden in corner of board, is a very small round 4 amp solder in fuse. Dark red in this case, with white lettering. This supplies 16 volts to various places.
I replace the fuse, having jimmied the interlock with a stack of business cards. I push power button. Color wheel spins up then light bulb starts shining. Shortly I have a bright pretty picture. I keep set a few days, running for background noise. I turn off when I leave, and on when I am in, just like normal people. Works perfectly. I tell owner not to be mad about bulb, he will need it at some point, and he is in good shape.
2 months later no complaints. It may well have been the ballast, which may have been bad and overloaded this fuse. I didn't put the old one back in, leaving well enough alone.Anyway, hopefully this may help someone else out here.
Danny