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.

"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

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

"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

"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.