How to test Inverter output voltages??

[electronicsurplus]

Does anyone know how I can test the output voltages from a LCD Power supply to determine whether there is any voltage coming out or not

I am not sure whether I should be testing for AC or DC. and, what would the approx voltage be basically?

I am trying to test a bunch of power supplies by using jumpers on the 5VSTB and PSon and BL-On or Inv-on.

I have all other voltages, 12V (Main Board), 18V (Sound)

Any help will be much appreciated

Thank you

[RON_CET]

Re: How to test Inverter output voltages??

if i'm reading you correctly your trying to measure the output voltages from secondary side of the inverter transformer going to the CCFL? If so that voltage extremly high AC and could very well damage most dvm.I would suggest an oscilloscope to measure,in most cases you can just hold your scope probe right near your inverter and you'll see the oscillation of the inverter working.

[electronicsurplus]

Re: How to test Inverter output voltages??

Ron,
You are correct. I am testing some power supplies which have inverters built in

I do not have an Oscilloscope but, by analogue Meter can go up to 1,000. even if I seen some type of jump of the meter. I can also use a ccfl bulb but, using a meter, for learning purposes

Thank you
Jon

[electronicsurplus]

Re: How to test Inverter output voltages??

Actually, do have an oscilloscope but, don't know quite how to use it yet

[budm]

Re: How to test Inverter output voltages??

Check the scope maximum input voltage it can handle, otherwise you will blow up the input circuits of the scope or the meter. The firing voltage for the CCFL can be from 1500~2000Vac, the sustain can be from 800~1000Vac.

[electronicsurplus]

Re: How to test Inverter output voltages??

Question:

There are 2 connectors to go to the bulbs. each with 2 pins. should
i test across the 2 pins on each connector or, across the 2 connectors?

I think the answer might also help other people wondering the same. i am sure I am not the 1st to wonder this

Thank you

[electronicsurplus]

Re: How to test Inverter output voltages??

Anybody know?

[selldoor]

Re: How to test Inverter output voltages??

I dont think anyone ever tries to test inverter output with a meter.
Remember most meters have quite thin leads and you are talking 1500-4000vAC.
Why dont you just use a testbulb- out of all the members on here you must be one of the best placed to set up a 2, 4, 6, or 8 bulb test frame.

[b700029]

Re: How to test Inverter output voltages??

There are high-voltage multiplier probes designed for things like these.

[electronicsurplus]

Re: How to test Inverter output voltages??

Thank you. I will make a panel setup

Was just trying to streamline the testing a bit

I remember using a High Voltage Probe years ago in CRT TV's. I wonder if they are still available. kind of looked like a long screwdriver with a meter on the end

Thank you gentlemen for your responses

[JimmysTGP]

Re: How to test Inverter output voltages??

New techs are not familiar with test tools like high voltage probes or deguasing tool or rejuvinator. I've already got rid of mine over 6 years ago. I carry around now one of those A/C test checkers that you can purchase at your local Electrical supply stores, to test for high voltage out of the inverter sections. Greenlee is a good one for this application.

[budm]

Re: How to test Inverter output voltages??

I am not sure if he wants to actually read the Voltage value or just want to find out if the transfromer is putting out high voltage, bad transformer may put out some voltage but not at the right voltage, so it depends on what you are looking for. One of the test SONY uses, is to put the meter (set to AC) probe on the connector plastic body, but not touching the output pin, then turn on the TV to see if the meter reading will jump up, this is just for finding out if it s putting out anything at all or completely dead, I myself do not use this test method.
You can do this: if you worked with RF transmitter you know why the lamp lights up.
http://s807.photobucket.com/albums/y...er%20testing/?
The lamp will not stay lit, this test is to find out if the transformer will put out enough AC to light the lamp or not, the inverter will go into shutdown since the lamp will no draw enough current to stop the protection circuit from kicking in.
Best test will be using spare lamps.
By the way, the HV meter for checking CRT HV, is for DC reading (the high voltage on the picture tube is positive to attract the electron beam from the Cathode Guns, it works the saem principle as vacuum tube), but you can buy AC/DC high voltage probe to use with your DMM.

[brian_au]

Re: How to test Inverter output voltages??

There are high-voltage multiplier probes designed for things like these.

Maybe you meant to say 'divider' probes?
Or multiply by 0.01 I suppose?

High voltage but not much current?
What I notice when testing with AC (on a good quality fluke meter) is that the probe draws a small arc from the inverter board output, with a bad lamp still connected. This is a pretty good sign the inverter board is still firing.

Just looking at a drop-in LED replacement right now for my particular screen, gonna buy one and see how good it is, if ok then will go that way with all CCFL faults instead of messing about with relatively short-life lamps