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Old 29th August 2009, 03:00 PM   #1
diyAudio Member
Join Date: Mar 2005
Default How to test a ballast for functionality

How would I test if my ballst is working on my DLP projector. Can I just remove the lamp and connect the to probes of the voltmeter where the lamp connector comes from the ballast or would that kill my voltmeter due to high voltage.

Would I connect it before the strike or after?
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Old 1st December 2009, 03:41 AM   #2
diyAudio Member
Join Date: Nov 2009
I am also curious about ballast testing. Anyone?
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Old 17th December 2009, 03:18 AM   #3
diyAudio Member
Join Date: Dec 2009
hello, i am currently in the same pickle u all are, i just wanted to mention that not all multimeters have capacity for such high voltages and you might fry it, i saw in another thread that there is 3 pins to look for in the same connection, and you simply jump short them, the same way turning on a motherboard works, and sensing the short, the ballast will turn on, but im not profficient in ballasts so please confirm this with someone else
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Old 31st December 2009, 02:42 AM   #4
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Join Date: Nov 2009
Join the two wires up and put a fuse in between. If it blows then at least the ignition is definitely working. :-)
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Old 8th January 2010, 03:06 AM   #5
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Join Date: Jun 2002
Location: non
best way to do this is using VERY high power and value resistors, a few comparators, and a latch with a large dummy load.

Basically, a circuit that is set to detect the ignition voltage, once detected it switches to a dummy load which pulls the current to tell the ballast to switch ignition off and sustain run voltage. which the second comparator detects and lights its LED saying run voltage is present.

Easiest way i know to do this.

Run voltage is present during the ignition sequence, but its not very stable until ballast senses the lamp is running and ignition is cut off..... only way to do this is to use a dummy load rated using ohms law to the proper impedence for the proper voltage and wattage. Which is switched via a relay on the ignition detection comparator. :P

For example if you have a 65V run voltage and its a 400watt ballast, you must perform ohms law to calculate the proper resistance to dump the proper current to pull 400watts so ballast doesnt shut down for a missing/bad lamp. this ALSO means you must use a resistor capable of dumping 400 watts!! otherwise, you must use an active load/current sink which uses high power transistors as load resistence.

Last edited by mbates14; 8th January 2010 at 03:09 AM.
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