Asus MK241H no power

[tibimakai]

I have picked up this monitor and it seems dead. No standby led, no standby voltage.
The only voltage I can measure is the 170V on the big cap.
I have found a bad FET transistor(Q101) which I have replaced and all the capacitors, just to be sure.
What else can I check?
I have made some pictures, they are not the best. I can make new ones tomorrow if needed.

[selldoor]

Re: Asus MK241H no power

Hi - I dont know how you can get pictures so good and pictures so bad in the same series. Anyway if you have 170Vdc at the big cap and nothing else. Id first check the
voltages coming out of the transformer.
On the pic of the back for the board bottom left just above the 16pin connector there is a component that looks to have
A1 or 1V on it - is its a fuse - can you test it.

[tibimakai]

Re: Asus MK241H no power

The pictures made from above were done on a stand and the side onese from hand.
The fuse checks out good. There are two more on the bottom, F101, F102 they are good too.

[jetadm123]

Re: Asus MK241H no power

Q101 was shorted, correct? There may be other components shorted, preventing the power supply from starting. What is the part number for IC200 (located on bottom of board)? And is it connected to Q101?

[tibimakai]

Re: Asus MK241H no power

It was shorted in every direction. Most likely you are right that is not only this Fet is out.
I will check it when I will get home.

[tibimakai]

Re: Asus MK241H no power

The IC is AS324AM-E1.

[retiredcaps]

Re: Asus MK241H no power

What else can I check?

See if the SMPS IC is shorted between Vcc and GND.

[tibimakai]

Re: Asus MK241H no power

There is 75.5kohm, so I guess it's not shorted.

[jetadm123]

Re: Asus MK241H no power

As odd as it sounds, the AS324 is a quad op amp. Not what we're looking for. We're looking for the pwm controller that drives Q101. On the heatsink that Q101 is mounted on there's another device mounted to it on the opposite side. What's the part number of it?

[tibimakai]

Re: Asus MK241H no power

K3568

[tibimakai]

Re: Asus MK241H no power

Q101 has
G=0.040V
D=168V
S=0.045V
Q(otherside)(hooked up flipped over can't see the number right now)
G=0.068V
D=168V
S=0V

[jetadm123]

Re: Asus MK241H no power

Not it either. Okay, on your fourth photo, there are two 8-legged chips towards the bottom. Looks like IC100 and IC102? How about their part numbers?

[tibimakai]

Re: Asus MK241H no power

If I measure between pin 1 and pin 4 on A324, I'm not getting anything 0V.

[tibimakai]

Re: Asus MK241H no power

There are two more ICs on the bottom:
EA1530A VCC=0V
L6562D VCC=0.133V

[jetadm123]

Re: Asus MK241H no power

There are two more ICs on the bottom:
EA1530A
L6562D

Great!

EA1530A is a TEA1530A power supply controller and the L6562D ia a power factor (PFC) controller.

You can test across pins 1 and 2 of the TEA1530 to test if Vcc and ground are shorted.

Test across pins 6 and 8 of the LD6562 to test Vcc and ground for a short.

At this point, I suspect pin 6 of the TEA1530 or pin 7 of the LD6562 are connected to the Gate of Q101. You can try using your meter to perform a continuity check to verify this. Sorry, but I must sign off for now. Hopefully, another member can take over.

[budm]

Re: Asus MK241H no power

OK, I look at the pictures, you will need to get the P/N on the SMPS and PFC IC.
Edited: OK, I see you got the P/N for the ICs.

[tibimakai]

Re: Asus MK241H no power

Found these two resistors suspect to me. The previuos owner mentioned about a pop before all went south.

[budm]

Re: Asus MK241H no power

They sure do look burnt up, cannot read the values any more, you will have to find out what pin of the IC they are connected to, then download the spec sheet of the IC to see what that pin/s do.
Man! Good pictures? What camera do you use? Is it that USB Micro scope? I forgot the model number you gave me.

[tibimakai]

Re: Asus MK241H no power

Forum is back and it's much more snappier, yeahh!
The pictures are made with the USB Microscope. This one, which is 2MP:
http://www.amazon.com/Celestron-Delu...usn+microscope
The resistors are from pin #5. I can't find resistor values anywhere on the net.
I have found some values from another Asus 19" monitor.
The resistors still have a value, one is 180KOhm and the other is 2.5MOhm(this one I haven't removed yet, it may have other value removed).
While the forum was down and I couldn't work on the monitors/TVs from the forum, I have fixed a LG L227WTG 22" monitor, and a Samsung 226BW 22" monitor, bad caps.

[tibimakai]

Re: Asus MK241H no power

Should I replace the resistors, or just leave them, since they have a value?
The values that I have found in another service manual for a 17" monitor, had much smaller values(1K and 22K).
I will just replace the EA1530A chip, it's cheap anyway and go from there.