Aoc n20wb

**budm** · 04-07-2018, 01:58 PM

Re: Aoc n20wb

Originally posted by ronhayes

MOSFET P/N are 4502c AA8 GAR.
Yes the tester can test all four ,So i connected all four but i only used it on its lower volts
Backlights came on and stayed on.

What I am trying to find out is how your tester function if you only has one lamp connected. Will it still light up the lamp when only ONE lamp is connected?
So did you check the resistance between S and D pins of the MOSFET?
AF4502 MOSFET.

Attached Files

AF4502C.pdf (471.1 KB, 3 views)

**budm** · 04-07-2018, 02:04 PM

Re: Aoc n20wb

Originally posted by vinceroger69

budm what was your thoughts on post 11 good or bad? as i couldnt find any specs on the transformer

I think his reading of 0.46 Ohm may be an error for the high Voltage winding, may be it is 0.46K Ohms?

**ronhayes** · 04-07-2018, 02:21 PM

Re: Aoc n20wb

Hi budm
any more info on these mosfets ?

**ronhayes** · 04-07-2018, 03:04 PM

Re: Aoc n20wb

I have connected the backlights to tester one at a time and all light up and stay on .
The resistance is 0.46k ohms
the resistance between pin 1 and 7&8 on both mosfets checked in the 200k range.
If you put the red lead on pin 1 and the black lead on pins 7/8 you get 21,7k but if you reverse the leads i:e black lead on pin 1 and red lead on pins 7/8 the resistance slowly rises to 55.7k.

**budm** · 04-07-2018, 05:10 PM

Re: Aoc n20wb

Originally posted by ronhayes

I have connected the backlights to tester one at a time and all light up and stay on .
The resistance is 0.46k ohms
the resistance between pin 1 and 7&8 on both mosfets checked in the 200k range.
If you put the red lead on pin 1 and the black lead on pins 7/8 you get 21,7k but if you reverse the leads i:e black lead on pin 1 and red lead on pins 7/8 the resistance slowly rises to 55.7k.

So your tester does not have protection circuit for open connection, the inverter circuit in the monitor will go into shutdown if any one of the lamps is bad or not connected, your tester will keep on driving the lamp and stay on even though only lamp is being tested.
I cannot find the spec for the transformer either, so 460 Ohms may be or may be not normal.
The MOSFET did show shorts between S and D so they may be OK since all we can test is the resistance not full function testing.

**ronhayes** · 04-07-2018, 05:23 PM

Re: Aoc n20wb

So does this point to the transformer being at fault ?

**budm** · 04-07-2018, 05:39 PM

Re: Aoc n20wb

I do not know, may be it should be removed and inspect the bottom side to see if it has any burn sign or not.

**ronhayes** · 04-07-2018, 05:58 PM

Re: Aoc n20wb

Here is a picture of the transformer removed it looks ok to me i can't see any burn marks ?

Attached Files

**budm** · 04-07-2018, 10:19 PM

Re: Aoc n20wb

It does look OK.

**ronhayes** · 04-08-2018, 03:06 AM

Re: Aoc n20wb

It measures the same out of circuit ?

**vinceroger69** · 04-08-2018, 04:25 AM

Re: Aoc n20wb

Originally posted by budm

It does look OK.

budm do you think ron could use one of these if needed and will it be easy to find the connection points for the wiring?
https://www.ebay.co.uk/itm/Universal...wAAOSwu4BVu1OW

**vinceroger69** · 04-08-2018, 04:26 AM

Re: Aoc n20wb

Originally posted by ronhayes

It measures the same out of circuit ?

ron when you first turn the monitor on do you get a quick flash of backlight like the 2 second too black fault

**ronhayes** · 04-08-2018, 04:45 AM

Re: Aoc n20wb

Yes Vince it does.

**vinceroger69** · 04-08-2018, 05:40 AM

Re: Aoc n20wb

that a lot of the time does mean a faulty ccfl or transformer, whats the best price you can get a replacement transformer for? also i use a old ccfl tube with connector on the end out of another old monitor/laptop and just plug it into one of the connectors on the psu too test for a faulty ccfl if then my temporary tube plus the monitors back lights stay on it proves the one tube i have disconnected is faulty inside the lcd assembly if that make sense.

**ronhayes** · 04-08-2018, 06:09 AM

Re: Aoc n20wb

Yes that does make sense .
But unfortunately i do not have a used ccfl tube that i can use ? I think the transformer is maybe ok and that it is probably more likely to be one of the cclf tubes ?
I think i read some where that you can use a old energy saving bulb or something like that ?

**vinceroger69** · 04-08-2018, 06:24 AM

Re: Aoc n20wb

yes budm posted a sticky on top of one of the threads i will see if i can find it

here it is
https://www.badcaps.net/forum/showthread.php?t=19987

**ronhayes** · 04-08-2018, 06:26 AM

Re: Aoc n20wb

I do have a tube that is in my magnifying glass would this do? it takes four 1,5v batteries to power it?

Attached Files

**ronhayes** · 04-08-2018, 06:39 AM

Re: Aoc n20wb

There are no markings on it but it shows in that link a update using a T5 similar to this ?

**ronhayes** · 04-08-2018, 06:46 AM

Re: Aoc n20wb

If this would be ok how do you connect it ? It looks like he has connected the wires on the crock clips and each crock clip connects to the two prongs at each end of the tube is that correct ?

**vinceroger69** · 04-08-2018, 11:42 AM

Re: Aoc n20wb

ron i sent the transformer seller on ebay a message asking if the knew the the winding readings this was there answer and bear with me ron once back at home i will look and see if i have some spare test ccfl tubes with leads/connectors if so i will post you one as these was free to me anyway out of cracked screen sets.
Hi. Primary resistence around 0.7 to 1.0 . Secondary resistence around 600 ohm i dont know if budm will cofirm if this sounds right as this was from the Chinese seller

Aoc n20wb

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