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PostPosted: Fri Jun 02, 2006 6:14 am 
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Black Belt
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Okay so I did measure them correctly .... so the lamps I have are a little over (1/4") 305mm so I would have to order the 305 they have .....

A guy that posted he worked on monitors stated he never had to change the backlight .... always the inverter ..... Is there a chance the inverter is bad instead of the backlight .... I do see a dim image .... would I have this symptom if the inverter were bad? Is there anyway to test it? :?

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PostPosted: Sat Jun 03, 2006 4:52 am 
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Mobo-fu Master
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As noted, the inverter puts out around 200 volts to a non-working tube to initiate the "fire-off" and produce a plasma. When the plasma arc is sustained, the voltage drops to around 50 volts.. depending on the length of the plasma arc. A decent multimeter should have the range up to 200 volts or so, to measure a non-loaded circuit. Use precautions to avoid shocks.
The inverter works on a constant voltage output, and a series resistor provides the voltage load drop when the lamp fires off. There is no pre-heat cathode in this type of lamp, so only one lead per end. The inverter is basically a small step-up transformer with a chopping transistor driving it at high frequency. Most of them do not have a heat-sink on the transistor that drives the core. They do overheat and fail. Any small common fluorescent tube could be used to test the inverter, such as an 8" two-pins-per-end type. Only one pin connection per end is needed. It should fire off as would the backlight tube. This will confirm the inverter is working. Most copiers use a similar setup to illuminate the page being copied, but some newer ones use LEDs instead of the fluorescent tube. The common power source for copier lamps is 24 VDC.

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PostPosted: Sun Jun 04, 2006 7:25 am 
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Black Belt
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Location: The Great State of Ohio
I took a look at the inverter board and I really don't know where to put my lead to test ... I'm really not to comfortable working with the power on.

What I think I will do is order the inverter and see if it works. I find it hard to believe both top and bottom backlights would go out at once. When the monitor start up for a second the lights are on.

Besides it will be easier to install the inverter board than having to solder the new backlights with the old wires and holders.

I'll see if they will take back the inverter if that's not the problem ...

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PostPosted: Sun Jun 04, 2006 9:04 am 
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Mobo-fu Master
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The inverter normally has a mini-plug that makes all connections.. it may even be a small daughter-board to the main board. The active circuitry is on one side of the transformer.. the side with no or few components is the output side. Look at the power transistor on the inverter board.. if it shows discoloration, it has run too hot.. and possibly is on the verge of total failure (or even the load resistor). You may be able to find a sub after-market replacement for it. That inverter could possibly be used as a fluorescent lamp supply for portable use.. as in the newer 'camp' lanterns.
The inverter may possibly be less expensive than the tubes!

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