Benq G2255 doesn't power on - amber power light when plugged in

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Did you look at my pictures on post 39 that I clearly marked where GNDs are?
Again, look at the left side of R802, it is connected to GND.
C805 is also connected in parallel with R802, the right side of R802/C805 are connected to pin 7 of the IC, so I do not see how you can say that one end of R802 is connected to pin 4!
Your picture here https://www.badcaps.net/forum/attach...6&d=1515675227
Clearly show the reading of 0.09V at TWO PLACES, both if them are GNDs. I do not see any arrow pointing to pin 4 at all.
See my new pix that I have marked again.
It looks like I am getting wrong DATA from you.
Are you sure you count the IC pins correctly or may be we are not looking at the same pictures same board?

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Hello Budm,

I'm sorry, I am still learning at this stage and your drawing makes it pretty clear what is ground and what is not. I was measuring the right pins, on the pins themselves.

I have attached annotated photos for the opposite side of the resistors to 5V and the voltages I get on the pins. I also measured the voltage on that point in Will62's photo for reference.

Please bear with me, I promise to listen and try and understand the first time

Many thanks for your help and guidance.

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

So at this point pin 4 (EN) does not look like it is being use to turn inveter circuit on/off like as shown in the circuit.
The two control signal lines seem to be going to pin 7 and pin 8.
May be you have to trace out and see if pin 4 is connected to anything else beside C802.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

I'm going to throw in a few notes:

1. You measured 5.5v on pin 1 (OV2). From the datasheet: "If the voltage at OV2 is always above 4.9V, the controller will treat this as a short circuit condition after a certain delay. The Fault Timer will
start ramping up."

2. In order to use external PWM dimming (pin 8), pin 7 must be pulled high
first. Is it possible that JW8 is covering 2 bases? Pulling pin 7 high, as well as activating pin 4 (enable).

3. It is possible that the solder point next to pin 4 is over a via to a sublayer
track that you can't follow. With power off, you could use your meter (resistance) to find where the track resurfaces.

4. A little odd that you measured 0v on pin 5. Over 1.2v is supposed to indicate that a fault has tripped the protection circuit. Shorting pin 5 to ground, bypasses the chip's protection circuit. (I would get Budm's advice before trying that.)

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

It is single layer board so that is just a pad for test point.
I sure like to get the correct diagram, I am sure we can bypass the protection circuit but I do not really want to do that but we may have to to do the test.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Has anyone ever purchased an S.M. from this site?

http://www.service-manual.net/ashop/...?product=56211

You might spend the $13, and get something generic, or similar to
what you've found for free.


Edit: Also, with power off, please check resistance between pin 4 and pin 7. There may be a trace under the chip. Thanks

[Dumah Brazorf]

Re: Benq G2255 doesn't power on - amber power light when plugged in

So the voltage at C801 is ~20V and at pin9 is 15,5V. What resistance is R804?
Check Q808 in diode mode for shorts.

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Has anyone ever purchased an S.M. from this site?

http://www.service-manual.net/ashop/...?product=56211

You might spend the $13, and get something generic, or similar to
what you've found for free.


Edit: Also, with power off, please check resistance between pin 4 and pin 7. There may be a trace under the chip. Thanks

Yep, I wonder if there is trace on pin 4 that goes under the IC.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

[/I][/B]
Yep, I wonder if there is trace on pin 4 that goes under the IC.

I tried to find a trace from pin 4, but it doesn't seem connected to anything, not even pin 7 which gives me 47 kohms resistance. Here is a picture with a light under the board.

So the voltage at C801 is ~20V and at pin9 is 15,5V. What resistance is R804?
Check Q808 in diode mode for shorts.

Dumah, not sure what you mean by this. I have a diode mode, but I check from wich pin to which pin and how do I see if there is a short? I tried reading from pin 4 to pin 5 (red on pin 4), pin 4 to pin 6, pin 4 to pin 7, pin 4 to pin 8 and and I get 1.5V reading in diode mode on all those pins. If I reverse my probes, I get from pin 4 to 5 and 4 to 6 - 0V, and from pin 4 to 7 and 4 to 8 - .75V???

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

I look real close at the pictures of the IC, the P/N as printed on the body is MP10091ES which I believe it is not the same as MP1009.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

I look real close at the pictures of the IC, the P/N as printed on the body is MP10091ES which I believe it is not the same as MP1009.

You are right, here is everything that is written on the IC:
MPS 1202
MP10091ES
BB845488A

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Hello Rddube,
That last pic really cleared up the trace routes. Can you take another with
the light further back, so that we can see the traces all the way to the back light connectors and the ap9962?

I'm including a pic that might help you check the ap9962. It's usually best to check them out of circuit, but you can try it and if you get weird results, just
unsolder the gate/source side, lift it slightly and retest.

Not sure what to think about pin 4 going nowhere. Most circuits that I've been
able to find using that chip, have the enable coming from the main board. Maybe default is enabled, until it is pulled low. It may be low now due to internal fault detection. (Have you ever checked to make sure that C802 is not shorted to ground?)

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Hello Rddube,
That last pic really cleared up the trace routes. Can you take another with
the light further back, so that we can see the traces all the way to the back light connectors and the ap9962?

I'm including a pic that might help you check the ap9962. It's usually best to check them out of circuit, but you can try it and if you get weird results, just
unsolder the gate/source side, lift it slightly and retest.

Not sure what to think about pin 4 going nowhere. Most circuits that I've been
able to find using that chip, have the enable coming from the main board. Maybe default is enabled, until it is pulled low. It may be low now due to internal fault detection. (Have you ever checked to make sure that C802 is not shorted to ground?)

Thanks Will, here is another pic. Checked C802 and left side is to ground and right side to ground I get 1.4K ohm.

In the pic you include what does 0L mean? Do I set my meter on diode for all tests, because at one point it says I should get low ohm?

Also, I have some AF4910N rated at 30V which is similar to the AP9962 which is rated at 40V, do you think I could try and substitute?

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

OK then MP10091... Pin 7 is enable.

Rddube: OL: open line/over limit. depends who you ask.
sorry, low reading, not ohms.



On the 30v part, not sure, need Budm's input there. You get a voltage spike
at cutoff. I haven't recognized any snubbing circuit to bring that down. You
can always try it.

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

OK then MP10091... Pin 7 is enable.

Rddube: OL: open line/over limit. depends who you ask.
sorry, low reading, not ohms.



On the 30v part, not sure, need Budm's input there. You get a voltage spike
at cutoff. I haven't recognized any snubbing circuit to bring that down. You
can always try it.

Man, I have been searching for the MP10091ES schematic, MP10091ES circuits and nothing really come up, nothing for the spec sheet either. Do you have the link where you get that from?
Finally clear out the confusion about the pin 4 of the IC. I am glad I took a closer look at the P/N of the IC.

[budm]

Re: Benq G2255 doesn't power on - amber power light when plugged in

The power MOSFET, you just check the resistance between S and D pin, since it is dual MOSFET so you will test resistance between S1 and D1, S2 and D2. it should show high resistance.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Yes, glad you caught that Budm.

The schematic is from a Philips 22" that uses the chip.

pdf

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

The power MOSFET, you just check the resistance between S and D pin, since it is dual MOSFET so you will test resistance between S1 and D1, S2 and D2. it should show high resistance.

Ok, did some tests in circuit for the power Mosfet. From S1 to D1 (there are 2 D1's) i get varying results, sometimes .5 MegaOhm, other times 47K and other times 475K ??? Same for S2 to both of the D2's.

However if I measure S2 to either of the D1's I get 1 ohm, meaning a short?

Should I remove the Mosfet (which will need hot air, I can do that) to test it?

I'm confused but sure am glad to have you gentlemen (Budm, Will62 and Dumah) looking over my shoulder! Thanks to you so much!!

PS - don't forget that this is the Power Mosfet for which I had mentionned in a previous post (#20) that there seems to be some heat marks under that chip, please see photo:

https://www.badcaps.net/forum/attach...4&d=1515532125

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in

Hello again gentlemen,

I said I had some AF4910N, they are installed on another scrap power board that I have and I tried removing one with hot air - what a mess.

The chips (there are 4, now 3 left) are covered with this transparent glue that I have never seen before which doesn't seem to melt when I heat it up. I put my hot air at 400F and I actually pulled the traces of the board off with the glue still holding them down. I think the chip is cooked.

Any idea how I can remove that glue before attempting the removal of the chip? Is 400F too high?

I didn't touch the power mosfet on my monitor power board. Only did some readings that I mention in the previous post.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in

When testing in circuit, you're dealing with other components in parallel. As Budm mentioned earlier, if you don't have a short between D and S, the chip is probably fine.
Look at the dual mosfet in the circuit pic in post #54. See how pin 7 is tied to pin 3? That's why you are getting a low ohms reading between D1 and S2.

On removing the chips, are you applying flux before heating? You should see the solder go soft when it's ready to lift. I would think the adhesive is softening by that time. You may need to pry beneath the chip to coax it. You can also lift each pin one at a time by using a dental pick (or similar) under the pin, as you heat the pin with your soldering iron. You don't need to lift much, a mm will do.

Now that we have a good pinout of the MP10091, can you go around and take voltage readings for each pin? An earlier reading that you took on pin 1, indicated a short circuit fault. I would like to see what the other voltages are. Also, somewhere along the line, you are going to need to check all caps for shorts, and resistors for open. I'll defer to Budm on what to try beyond that.