Asus VE205 .... 2seconds to black

[alexanna]

Re: Asus VE205 .... 2seconds to black

You measured the power supply voltage to the controller; Let me get back to that in a moment.
Measure the enable or back light on voltage positive lead on pin 16 lead,what voltage reading do you get with the back lights on and off?

[Welchs101]

Re: Asus VE205 .... 2seconds to black

Sorry, measured the wrong thing.

Using pin 16 (ENA pin) and pin 5 (as gnd).

Power on the monitor and LED light turns blue...........
Pin16 DC voltage relative to pin 5 is........2.9Volts

when LED light goes orange the Pin16 value drops to 0.1Volts

Is this what you wanted measured? If not just let me know.

[alexanna]

Re: Asus VE205 .... 2seconds to black

ok, reconnected computer to monitor
powered on computer
powered on monitor

LED light comes on as blue and stays blue..........screen will flash with computer desktop but then goes blank...........even after monitor goes blank LED light is blue.........

Do you still have a siginal going to the monitor when you are checking voltage to the controller?

[Welchs101]

Re: Asus VE205 .... 2seconds to black

hummmm......good question. I did not connect the computer....let me do that and repeat the measurements. sorry about that.

[Welchs101]

Re: Asus VE205 .... 2seconds to black

with computer connected............

P16 initially is at 2.9Volts........

then fluctuates to around 0.1V

then fluctuates back to 2.9V and just stays there

LED light stays blue entire time during measurement

[alexanna]

Re: Asus VE205 .... 2seconds to black

Good,now would you measure pin 11 VDDA.
With a signal applied to the monitor.

[Welchs101]

Re: Asus VE205 .... 2seconds to black

pin 11 with computer connected relative to pin5 (gnd) is 5.0V.

[alexanna]

Re: Asus VE205 .... 2seconds to black

When monitors first turn on they go through a self test of the inverter. By turning the back lights on to full brightness to check for proper voltage and current flow. So the back light on voltage starting high and going low and then going back high in my opinion is OK.
As long as pin 11 VDDA stays the same when the backlights are on and off, that also should not be a problem.
Even if a schematic was available this would be a difficult one to diagnose.
At this point I am out of ideas.

[Welchs101]

Re: Asus VE205 .... 2seconds to black

alexanna, i really appreciate your help......thanks.

lets see if anyone else on here has any ideas. if not, no worries, as i said i was trying to do my neighbor a favor by fixing but with all the "black friday" deals going on they should be able to get a new monitor cheap......not as cheap as "0" but still cheap.............

[Welchs101]

Re: Asus VE205 .... 2seconds to black

Just curious about the IC Alpha-Omega 4614......

IC: alphaomega 4614
https://cdn.badcaps-static.com/pdfs/...0e94bf963c.pdf

How to make measurments to verify this is a good part? Any ideas?

[retiredcaps]

Re: Asus VE205 .... 2seconds to black

How to make measurments to verify this is a good part? Any ideas?

For mosfets, I check for shorts between source-gate, source-drain, drain-gate. The AO4614A has two of each.

So test S1-G1, S1-D1, G1-D1, S2-G2, S2-D2, G2-D2. Any reading under 30 ohms suggests a short. I normally test "in circuit" and if I get a reading under 30 ohms, then I desolder and retest.

Others test mosfets like this ...

http://www.4qdtec.com/mostest.html

[Welchs101]

Re: Asus VE205 .... 2seconds to black

There are two alpha omega 4614 chips..........they both measure the same

S1-G1: PINS 3,4: 5.1Kohm
S1-D1: PINS 3,6: 1meg to 3megohm
G1-D1: PINS 4,6: 1meg to 3meg ohm
S2-G2: PINS 3,4: 10.1Kohm
S2-D2: PINS 3,6: 2meg to 3megohm
G2-D2: PINS 4,6: 2meg to 3meg ohm


so i guess these are ok........

any ideas on other things to check?

[Rtech]

Re: Asus VE205 .... 2seconds to black

Although the resistance readings look ok, they still do not confirm for certain if they are working.They are complimentary mosfets,and need to be tested to see if they do switch on and off.It may be worth a try doing that using the diode test function on your meter,hope the following helps, if you are not sure what to do.The system shown still applies to your mosfet drivers even though they are not 3 pin devices.
http://www.4qdtec.com/mostest.html

[Welchs101]

Re: Asus VE205 .... 2seconds to black

hi,

ok. i followed the directions of the link.

on diode check mode:NPN device
On say one of the IC's i put the blk lead to the source S1 and then touch the gate G1 (red lead) for about 2 sec then place red lead onto the drain D1. The voltage reading starts out at ~ 2V then increases until i guess it maxes out the diode check meter at ~ 2.5V.

I then repeat this on the other IC-4614. However, on this one i can get a reading once i place the red lead onto the drain. I go back to the first IC and try and repeat the procedure and i cant get a reading. If i wait a while and repeat the procedure on the first IC i can sometimes get a reading like i did the first time. But i cant get a reading on the 2nd IC no matter what i do.

Is this the only way to check the IC? I dont read any shorts as best i can tell.

Have not checked P-channel devices yet.......wanted to make sure i was doing it correct first.

[Rtech]

Re: Asus VE205 .... 2seconds to black

just maybe they need to be out of cct.

[Welchs101]

Re: Asus VE205 .... 2seconds to black

is there some way to test it in circuit .........maybe while its powered on? To see if the device is working as it should?

[Welchs101]

Re: Asus VE205 .... 2seconds to black

anyone have any thoughts?

[PlainBill]

Re: Asus VE205 .... 2seconds to black

anyone have any thoughts?

The AO4614 is a complementary pair of enhancement mode mosfets. What the big words mean is it contains one N-channel and one P-channel mosfet.

The test you are doing is for an N-channel mosfet; for a P-channel you would reverse the leads, and should get a similar result.

The fact that you get a brief reading on the first IC indicates it is working; there are several reasons you might not get a reading on the second IC, one of which is it may be defective. Another possible reason is the components driving the gate are turning it off quickly.

The best approach is to remove it from the circuit board and test. A second approach would be to rig up a tester which would allow you to maintain the voltage on the gate while checking the source-drain voltage. That could be as simple as a second DMM with diode test mode.

PlainBill

[Welchs101]

Re: Asus VE205 .... 2seconds to black

interesting........never thought about using another DMM. Let me see if i can find one............if that does not work then i may just ahve to remove the IC from the circuit.

thanks for the ideas.

[Welchs101]

Re: Asus VE205 .... 2seconds to black

i could not find another DMM so i think i am just going to try and take the IC out.

I did have a question though. If it is bad...........i looked online to find a replacement and .........i couldnt find one.

I checked digikey but they dont have any all they have is a AO4612 but i am not sure this would work. Any ideas on where to find a replacement part?