Asus VE205

[eckertb83]

Hello everyone,

I've recently been given an Asus VE205 monitor, of course it has problems....

When I plugged it in for the first time and pressed the power button nothing came on. Nothing on the screen, power LED dead. I pulled everything apart to get the boards out. To my surprise it was fairly easy not to mention cheaply built. Once I got the Power Inverter board out it actually looked fine, compared to others I've seen (knowing looks are deceiving) . I ended up checking the fuse right behind the power plug and my multi meter showed "1" . I de soldered the fuse and replaced (T2AH250v). I had the same fuse in house but without the pigtails, so I added a fuse holder instead. Put it all back together and still no power led or anything.

Should I just go ahead and replace the caps aswell or is there something else I should be looking for?

[Rtech]

Re: Asus VE205

Photos will certainly help to get you the right guidance.Also the first thing to check is the DC voltage across the large capacitor on the board this will be approx 1.6 times you mains input voltage.EXtREME CARE SHOULD BE TAKEN if you are not used to taking live voltage measurements.

[eckertb83]

Re: Asus VE205

Thanks I'll try that and I report back with pictures.

[eckertb83]

Re: Asus VE205

I'm a bit rusty when it comes to checking a live voltage on large cap. Can someone point me in the right direction, Ive tried searching here and google and couldnt find anything specific. My thought was plug power in and measure the volts between the 2 leads on the big cap. If the cap says 400v my reading should be about 640v correct??

Thanks in advance

[budm]

Re: Asus VE205

What is your country line voltage? Just multiply that number by 1.414 to get the expected DC right at the two legs of the cap, just do not touch ANYTHING with your hands.

[eckertb83]

Re: Asus VE205

Line voltage is 120v = 169.68v Thanks I check it tomorrow and post pics

[eckertb83]

Re: Asus VE205

Ok I pulled the monitor back apart to get a live reading and take pictures. Plugged the board in and tested the 2 legs of the big cap with DMM and shows 0
No power.... unplugged it and tested the fuse again... Blown (although it doesnt look blown, not black marks)......DMM reads 1.

SO first I need to figure out why i keep blowing a fuse?

I've added pic of both the power and signal board fronts and backs.

[budm]

Re: Asus VE205

That means it may have shorted bridge rectifier, shorted out Power MOSFET (the one next to that big green main DC filter cap).

[eckertb83]

Re: Asus VE205

Is there a test to confirm that?

the numbers on that bridge rectifier are
first line: p9njl2
Second line: k3530

While trying to read the numbers I noticed the Orange Cap (just in front) has a brown burn mark and a hair line crack.

[budm]

Re: Asus VE205

You can Google how to test bridge rectifier with meter, the MOSFET on that heat sink, just measure the combination of the 3 pin, as you look at the MOSFET facing you, make left pin as pin 1 then proceed to test using your Ohm meter.
Pin 1 & 2
Pin 1 & 3
Pin 2 & 3

[eckertb83]

Re: Asus VE205

ok tested the bridge rectifier

Pos lead on pin #1
1 to 2= 1249
1 to 3= 1249
2 to 3 = 004

Neg lead on pin #1
1 to 2= 642
1 to 3 =642
2 to 3= 004

according to the 2 videos i watched on youtube the bridge rectifier is good. If I heard them correctly.
The cap just in front it burned out its a 101k 1kv cap. Im gonna buy some and replace it then go from there.

If you look at the pic in my previous post you see the burn mark the other side of it is burned open.

[budm]

Re: Asus VE205

The bridge rectifier that needs to be checked is in the primary side and it has 4 legs. It is sitting next to the small blue cap.
The reading that you reported on post 11, what rectifier is that one? Not the MOSFET mounted on the heat sink next to that large blue (light green?) DC filter cap? That reading you post is for the MOSFET per your picture on post 9. If pin 2 and 3 shows 004 Ohms, that is bad but can be due to that burnt cap since that cap is connected in parallel with pin 2 and 3 of that MOSFET, so take out that cap and see if the pin 2 and 3 will show higher Ohm reading with the cap removed.
By the way, based on the picture of the MOSFET: Left pin is Gate, Middle pin is Drain, right pin is Source. Common failure is shorted Source and Drain.

[eckertb83]

Re: Asus VE205

Ok thanks I'll test that primary side and remove the cap. Then test the MOSFET again. Any idea where I can get that cap? I did a quick search on for it on google and most I could find were from china, I checked mouser but couldn't find it there either.

[budm]

Re: Asus VE205

100pF 1KV:
http://www.mouser.com/ProductDetail/...oPwRnO4XtizpdU

[eckertb83]

Re: Asus VE205

Ok so checked the primary side rectifier and took the cap off and rechecked the mosfet.

Numbers as follow.
Primary side qith neg probe on pin1

1-2-557
1-3-554
1-4-539
2-3-1
2-4-550
3-4-576

The Mosfet
G-S-620
G-D-620
D-S- 002
No real change so need to replace this as well and im assuming the primary needs replacing as well.

[budm]

Re: Asus VE205

"D-S- 002" is that 2 ohms? If it is, it is shorted out, you should remove it from the board and take the reading again.
Same for "2-3-1" is that 1 ohm?

[eckertb83]

Re: Asus VE205

I was using the diode mode thats on my DMM. So no its not ohms checking resistance. I will remove both and recheck them. Then post back

[eckertb83]

Re: Asus VE205

Ok finally got around and de soldered both yhe mosfet and primary rectifiers. I tested both using ohm and diode modes on my DMM.

Mosfet
Diode mode. (Ohms)
Neg lead on pin 1 (G)
1-2=1 (1)
1-3=1 (1)
2-3=540 (1)

Primary. (Ohms)
Neg lead on pin 1 (+)
1-2=555 (1)
1-3=556 (1)
1-4=1249 (1)
2-3=1 (1)
2-4=541 (1)
3-4=570 (1)

[eckertb83]

Re: Asus VE205

Can someone tell me how to ID the specs of both the mofet bridge rectifier and primary rectifier so I can order new ones. I tried searching the numbers on both and couldn't find anything. I even tried searching mouser for the part #'s and couldn't come up with an answer.

[eckertb83]

Re: Asus VE205

After looking through some other treads I think I may have some readings that aren't correct. So my question is when taking an Ohm reading what setting should I have it on? I have a cheap harbor freight 7 Function DMM ( http://www.harborfreight.com/7-funct...ter-98025.html ) I'm pretty sure my diode reading are correct but my ohm's may have been tainted.
Thanks for All the help so far