help me to test transfromer? - Badcaps

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mattstolte

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Join Date: Dec 2013

Posts: 612

Country: usa
#1

help me to test transfromer?

08-24-2015, 10:29 AM

im trying to find which transformer is bad can anyone tell me how to test these? I was told to Ohm out the secondary (small windings) of each transformer to find the one that reads >0
but I don't know what windings are ive never learned how to test a transformer please help with pictures also if you can thanks
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johnboy1313

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Join Date: Nov 2012

Posts: 1959

Country: USA
#2

08-24-2015, 10:47 AM

Re: help me to test transfromer?

http://lmgtfy.com/?q=how+to+test+a+t...mer+with+a+dmm
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stj

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#3

08-24-2015, 11:20 AM

Re: help me to test transfromer?

those transformers have cracked soder joints.
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R_J

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Posts: 9515

Country: Canada
#4

08-24-2015, 04:41 PM

Re: help me to test transfromer?

Measure the secondary of each transformer (circled in yellow) It should read around 900 - 1100 ohms, but each of the 4 transformers should read the same if one is lower or higher it is most likely the bad one.
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keeney123

Lauren

Join Date: Sep 2014

Posts: 2536

Country: United States
#5

08-24-2015, 08:06 PM

Re: help me to test transfromer?

Are these transformers to CCFL backlight to a Screen or monitor?
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mattstolte

Badcaps Veteran

Join Date: Dec 2013

Posts: 612

Country: usa
#6

08-26-2015, 09:26 AM

Re: help me to test transfromer?

these are for a 32 inch emerson lcd, I put my meter on 200k ohm they all read 112-115 the tv turns on them after 30 seconds shuts down
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SteveNielsen

Retired Tech

Join Date: Jun 2012

Posts: 2327

Country: USA
#7

08-26-2015, 09:47 AM

Re: help me to test transfromer?

Originally posted by stj

those transformers have cracked soder joints.

I don't see any cracked solder joints from the pics. Please point them out for us.
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keeney123

Lauren

Join Date: Sep 2014

Posts: 2536

Country: United States
#8

08-26-2015, 11:51 AM

Re: help me to test transfromer?

You can tell which is bad when you first turn on. It will be the one going to the backlight that does not light. Are you sure you do not have a bad backlight? That can be check by opening the panel looking at the one that does not light and then changing it with one that lights. Usually the input voltage is check on these transformers as the input voltage is small compared to the output voltage.
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johnboy1313

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Join Date: Nov 2012

Posts: 1959

Country: USA
#9

08-26-2015, 12:04 PM

Re: help me to test transfromer?

Have you checked the wiring to the ccfl's?
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stj

Great Sage 齊天大聖

Join Date: Dec 2009

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Country: Albion
#10

08-26-2015, 12:24 PM

Re: help me to test transfromer?

Originally posted by SteveNielsen

I don't see any cracked solder joints from the pics. Please point them out for us.

probably more - the blured pic dont help!
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CAIIIA

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Join Date: Mar 2012

Posts: 14

Country: Russia
#11

08-26-2015, 01:56 PM

Re: help me to test transfromer?

Please use translator. this my post. http://televid-sib.ru/index.php?topic=4798.0
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SteveNielsen

Retired Tech

Join Date: Jun 2012

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Country: USA
#12

08-26-2015, 02:12 PM

Re: help me to test transfromer?

Originally posted by stj

probably more - the blured pic dont help!

I consider it to be inconclusive. It is just too blurred to tell. Nothing looks shiny where it is that far out of focus.
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CAIIIA

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Join Date: Mar 2012

Posts: 14

Country: Russia
#13

08-26-2015, 02:17 PM

Re: help me to test transfromer?

Ok. Add full picture.
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Last edited by CAIIIA; 08-26-2015, 02:20 PM. Reason: edit
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R_J

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Join Date: Jun 2012

Posts: 9515

Country: Canada
#14

08-26-2015, 03:45 PM

Re: help me to test transfromer?

try only hooking up one ccfl at a time, disconnect lamps 2,3, & 4 and see if the # 1 light flashes on. then disconnect #1 and connect #2, then repeat with lamp 3 & 4. if a lamp does not light (for example #2) connect #2 lamp to transfomer #1 or #3 and see if it lights.
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keeney123

Lauren

Join Date: Sep 2014

Posts: 2536

Country: United States
#15

08-26-2015, 04:47 PM

Re: help me to test transfromer?

Originally posted by CAIIIA

Ok. Add full picture.

So I do not know if op has a scope, etc. to measure 800 volt P to P on 100 usec div.
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