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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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metal halide bulbs testing?
Hi all, I have an sharp XG-E3500U lcd projector that i'm trying to repair,
I've purchased a copy of the service manual (email me off list if you'd like a copy) and have a pretty good idea of how things are working. when i got the unit, the main fuse on the power board was blown and the person who gave it to me suspected that the power supply was bad. when i replace the fuse and power up, the lamp arcs 2-3 but never lights. the fuse blows immediately afterward. my assumption is that either the warm-up arc isn't able to ignite the lamp because it's bad, or that the lower voltage componant supplied by the ballast is isn't there so the thing keeps pulsing then blows a fuse. Will a bad bulb cause a fuse to blow because it won't conduct a current after being hit with the warm up arc? I figured I'd send a message to the list to get an opinion before i spend $300 on a new bulb.. maybe i need to focus more on trouble shooting the ballast. Is there an easy check for visual or electronic signs of a bad metal halide bulb? Thanks for any help, Steve p.s., please don't warn me about the high voltage.. i may sound like a novice but my heart is healthy and i'm quite intent on getting this thing to work. |
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"Steve Vitale" wrote in message ... | Hi all, I have an sharp XG-E3500U lcd projector that i'm trying to repair, | I've purchased a copy of the service manual (email me off list if you'd | like a copy) and have a pretty good idea of how things are working. when i | got the unit, the main fuse on the power board was blown and the person | who gave it to me suspected that the power supply was bad. when i replace | the fuse and power up, the lamp arcs 2-3 but never lights. the fuse blows | immediately afterward. my assumption is that either the warm-up arc isn't | able to ignite the lamp because it's bad, or that the lower voltage | componant supplied by the ballast is isn't there so the thing keeps | pulsing then blows a fuse. Will a bad bulb cause a fuse to blow because it | won't conduct a current after being hit with the warm up arc? I figured | I'd send a message to the list to get an opinion before i spend $300 on a | new bulb.. maybe i need to focus more on trouble shooting the ballast. Is | there an easy check for visual or electronic signs of a bad metal halide | bulb? Thanks for any help, Steve That's backwards. I'd suspect the ballast, not the lamp. Is the ballast inductive or solid state? I'd try hooking up a 100 W light bulb as a test to replace the lamp, disconnecting the starter system if possible. If the lamp glows fully or not at all I'd suspect the ballast. N |
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That's backwards. I'd suspect the ballast, not the lamp. Is the ballast
inductive or solid state? I'd try hooking up a 100 W light bulb as a test to replace the lamp, disconnecting the starter system if possible. If the lamp glows fully or not at all I'd suspect the ballast. N I assume that it's an electronic ballast as it uses transistors to limit current as opposed to a coil. i assume those should be keeping things from reaching a current where a fuse would blow? i think this is starting to make a bit more sense. Thanks |
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"Steve Vitale" wrote in message ... | That's backwards. I'd suspect the ballast, not the lamp. Is the ballast | inductive or solid state? I'd try hooking up a 100 W light bulb as a test to | replace the lamp, disconnecting the starter system if possible. If the lamp | glows fully or not at all I'd suspect the ballast. | | N | I assume that it's an electronic ballast as it uses transistors to limit | current as opposed to a coil. i assume those should be keeping things | from reaching a current where a fuse would blow? i think this is starting | to make a bit more sense. | Thanks Much more likely one of those has punched through. Replace them or find a way to test them under voltage. N |
#5
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"Steve Vitale" wrote in message ... That's backwards. I'd suspect the ballast, not the lamp. Is the ballast inductive or solid state? I'd try hooking up a 100 W light bulb as a test to replace the lamp, disconnecting the starter system if possible. If the lamp glows fully or not at all I'd suspect the ballast. N I assume that it's an electronic ballast as it uses transistors to limit current as opposed to a coil. i assume those should be keeping things from reaching a current where a fuse would blow? i think this is starting to make a bit more sense. Thanks If the fuse blows you have a problem with the ballast. An electronic ballast still uses a transformer, it's more like a switching power supply in a PC, monitor, etc, but rather than regulate the output voltage it regulates the amperage as well as provides a high voltage spike to strike the arc. Check carefully for shorted semiconductors in the ballast circuit. |
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