I am aware of the precautions necessary considering the high voltage. I am
trying to determine if this dark LCD screen on a Compaq Presario 900 is the
result of a bad lamp or if it is the inverter. I have the tube exposed and
have measured 2200v start up voltage, then after a short time the lamp goes
black and voltage across the lamp measures 0v. Is this telling me what I
think it is, that the inverter or prior is the culprit here? Or is this
impossible to measure with my Fluke 77 multimeter?

Thanks for any help!!!

Rob

"Rob" wrote in message
...
I am aware of the precautions necessary considering the high voltage. I am
trying to determine if this dark LCD screen on a Compaq Presario 900 is
the
result of a bad lamp or if it is the inverter. I have the tube exposed and
have measured 2200v start up voltage, then after a short time the lamp
goes
black and voltage across the lamp measures 0v. Is this telling me what I
think it is, that the inverter or prior is the culprit here? Or is this
impossible to measure with my Fluke 77 multimeter?



Some inverters will shut down if they detect a faulty lamp, try connecting a
new lamp to the inverter and see if it works, you don't have to take the
time to install it, just wire it up. Alternatively you could connect a
surplus inverter to the lamp you have and see if it comes on.

I have written in another thread about similar problem (Thinkpad laptop
LCD display). This weekend I took the CCFL from a display that has a
cracked front glass and connected it to the one that would not light
up. It worked! So then I tested two other used inverters that I thought
were bad. One worked fine too, and the other would cause the CCFL to
just flash on and off. So I have to assume that maybe the second
inverter is bad or marginally detect an overcurrent load.

Analogy: as a typical 48" fluorescent tube(s) at home starting to age,
it either stop coming on or the tube started to dim and flicker.
Usueally the ballast is ok, but the tube has probably reached the end
of life.


Some inverters will shut down if they detect a faulty lamp, try
connecting a
new lamp to the inverter and see if it works, you don't have to take
the
time to install it, just wire it up. Alternatively you could connect
a
surplus inverter to the lamp you have and see if it comes on.

"Rob" writes:

I am aware of the precautions necessary considering the high voltage. I am
trying to determine if this dark LCD screen on a Compaq Presario 900 is the
result of a bad lamp or if it is the inverter. I have the tube exposed and
have measured 2200v start up voltage, then after a short time the lamp goes
black and voltage across the lamp measures 0v. Is this telling me what I
think it is, that the inverter or prior is the culprit here? Or is this
impossible to measure with my Fluke 77 multimeter?

You're saying the lamp lights for a short time and then goes out?

If so and the ends aren't darkened, it could be an inverter problem.

As others have suggested, easiest is to substitute a working lamp to be
sure.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.