need help to test inverter transformer

[selldoor]

Re: need help to test inverter transformer

I cannot see that we have ruled out the bulbs or wiring being bad? Have you any spare bulbs or any old lcd screen.


Can you re check the secondary winding resistance on the 3 transformers report result as
T1 s1>s2 = xxxohms
T1 s3>s4 = xxxohms and so on

[woaimi]

Re: need help to test inverter transformer

any other idea? I get the correct voltages from the connector as the stamp on board indicated.

[woaimi]

Re: need help to test inverter transformer

It would stay on with the standby light but the screen goes away after a few seconds, may be I should replace the last of the 3 inverter transformer as well.

[retiredcaps]

Re: need help to test inverter transformer

any suggestion are much appreciated. Thank you

Plug in a source and see if it stays on.

[woaimi]

Re: need help to test inverter transformer

Well, I decided to mounted the board back in place and try since I pretty much run out of option. Plugged in AC and power it on. It actually came on and screen went away after about 5 seconds. The standby led is on still after the screen went away. I can turn it off and on and the screen would be on again for about same amount of time.

Replacement parts so far:
2 x inverter transformers (burnt)
1 x diode (nothing wrong but since I got it off the board might as well replace it)
2 x radial fuses
and all filter capacitors got de-soldered and re-soldered back in.

any suggestion are much appreciated. Thank you

[woaimi]

Re: need help to test inverter transformer

well I de-soldered all 3 schottky diodes (photo attached) and test them using the diode test and they seems to be working. The primary and secondary filter capacitors were also de-soldered and test using capacitor test mode, them too were fine. I have not test the transformer and the "optoisolator" (guessing) as some reading material point out.

Can anyone suggest how to test the transformer and the "optoisolator"? Other than that I run out of option, might just give up.

the 1st photo is EN220A
the 2nd photo is W2206, the 2 diodes that I couldn't find any info.
the 3rd photo is from what I'm guessing is the "optoisolator"

[woaimi]

Re: need help to test inverter transformer

I found this testing method from Tomm66 in this forum to test EN220A
<<<<<<
Number pins 1-3 left to right.
Labelled (pos/red) (neg/black) respectively (use diode test.)
Test 1-2 should read ~150 - 700.
Test 2-1 should read single "1" or "OL".
Test 2-3 should read single "1" or "OL".
Test 3-2 should read ~150 - 700.
Test 1-3 should read single "1" or "OL".
>>>>>>
and the result
1-2= 159
2-1="1"
2-3="1"
3-2= 159
1-3= "0.00"

meanwhile from a user name multimeter's suggestion on that same thread
<<< set your meter if dmm to 200 ohm,or 10k ohm anologue, pin 1 and 2 should show reading one way ,pins 2 and 3 should show reading one way >>>>
it shows reading only one way 1-2 & 2-3 as I flipped the probes, i got "1"

couldn't find any info for pair of W2206 diode.

[woaimi]

Re: need help to test inverter transformer

Yes those are diodes some examples are here
http://www.westfloridacomponents.com...ierDiodes.html

Can you make out any part numbers on them?

they are
1x EN220A
2x W2206

they all indicate having common cathode in the middle lead

[woaimi]

Re: need help to test inverter transformer

What same readings 1 and 1 or 1 and 597 ?

the readings were 1 and 597 consistently. I have not solder it back, planned to replace it just in case.

[selldoor]

Re: need help to test inverter transformer

Should those diodes (i think) on the secondary be concerned? These devices look like transistors with 3 leads but the board indicates with Dxxx.

Yes those are diodes some examples are here
http://www.westfloridacomponents.com...ierDiodes.html

Can you make out any part numbers on them?

[selldoor]

Re: need help to test inverter transformer

done it many times since then and getting the same readings. .

What same readings 1 and 1 or 1 and 597 ?

[woaimi]

Re: need help to test inverter transformer

done it many times since then and getting the same readings. there are only the caps and resistors are untested in the primary. Should those diodes (i think) on the secondary be concerned? These devices look like transistors with 3 leads but the board indicates with Dxxx.

[retiredcaps]

Re: need help to test inverter transformer

got the measurements includes in the photo. there was 1 (the one with 597 &1) initially was 1 & 1 in both direction. I desoldered it, retested still 1 &1, 15 mins later before i post result i retested again, that's when it gave me 597 &1

The above is odd behaviour. I would retest that diode again out of circuit maybe every 15 minutes and check the results again.

[woaimi]

Re: need help to test inverter transformer

got the measurements includes in the photo. there was 1 (the one with 597 &1) initially was 1 & 1 in both direction. I desoldered it, retested still 1 &1, 15 mins later before i post result i retested again, that's when it gave me 597 &1

[retiredcaps]

Re: need help to test inverter transformer

Okay, so now that you understand the mosfets are not shorted, there are 4 other diodes in the primary section (as outlined on the pcb by the dotted line) that are suspects in causing the fuse to blow.

Test all 4 in circuit first using the diode test function on your multimeter. Report all your readings. Again you should have 2 readings per diode. If any of them look suspicious, then desolder them to verify out of circuit.

[woaimi]

Re: need help to test inverter transformer

sorry for my previous senseless comment, i was typing my own thoughts (like thinking out loud). It wasn't 1 ohm, it was the 1 on the left side of the screen.

thanks for that very useful tutorial

[retiredcaps]

Re: need help to test inverter transformer

usually if something out of range I would be able to see the display flashes some value then go to 1. Not this case, number 1 remain the same as an open circuit.

You are not correct in your interpretation. I think you need to re-read post #23 again.

If my explanation isn't clear, then try

http://www.sparkfun.com/tutorials/202

[woaimi]

Re: need help to test inverter transformer

usually if something out of range I would be able to see the display flashes some value then go to 1. Not this case, number 1 remain the same as an open circuit. i'll probably replace them anyway. what's bad?

[retiredcaps]

Re: need help to test inverter transformer

mosfet #1
G-D = 1
G-S = 1
D-S = 265K

mosfet #2
G-D = 1
G-S = 1
D-S = 269K

If that is 1 ohm, then both mosfets are definitely shorted and bad. If it is out of range, then the mosfet is good. So which is it?

[woaimi]

Re: need help to test inverter transformer

mosfet #1
G-D = 1
G-S = 1
D-S = 265K

mosfet #2
G-D = 1
G-S = 1
D-S = 269K