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

I would put the scope pin on the GATE drive pin and keep it there then power up the board and you should see the drive signal, if the drive signals are present for both GATE that means the inveter transformer primary will get the drive Voltage and will try to fire up the lamp if that does not happen then to protection will kick in, or if it detects over current when the MOSFET are driven, the protection also kicks in, this will happen very fast. the circuit will have to try to drive the lamps first if there is problem (I.E lamp do not conduct) within set time then protection will kick in.
The typical protection circuit used in the CCFL will shutdown the circuit:
1) It will detect if the lamp will conduct current and stay conduction when the Firing Voltage is applied to the lamps, if the lamps do not conduct then the shutdown occur. The detection circuit detect the error on the lamp return side of each lamp, so one bad lamp will shutdown the circuit. Some circuit may try to fire up the lamps up to three times.
2) if the lamps are not connected then it will detect no lamp current flow due to no load connected so you do not want to have over 1000V at the lamp connector present without load otherwise it will start arcing to the near by circuit.
3) Over current will also shutdown the circuit.
Some circuit may have 3 seconds timer, if the false is present during the first 3 seconds then the circuit is shutdown, thus 3 seconds to black, everything has to be working within 3 seconds for the circuit to stay on.
The MP1009 looks to have only 300mSec.

[will62]

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

OK, chip appears shut down. I'm adding another pic with the voltages you measured. About this time, I'd be looking for gate pwm signal with the oscope.
But you won't see it if chip is down. Let's see what Budm recommends.

One oddity: Both gate drives should be 0V if chip is down. You have 0V on BG (bottom), But 13V on TG (top).

[rddube]

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

Will62: You asked me if I have an oscilloscope in another thread, and yes I do. It is a very basic one JYE Tech DSO138 (those small chinese Oscilloscopes that come in a kit) but it works!

[rddube]

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

Can you flip your meter over to AC and remeasure pins 1,2,3 & 16?

Switching my meter to AC gives me the following:

Pin 1: 15.4mv dropping
Pin 2: 5.5mv dropping
Pin 3: 15.2mv dropping
Pin 16: 21.6mv dropping

[rddube]

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

Maybe you should use a 10k resistor for the white connection.
Check resistance of your lamps leads and on the blue high voltage caps.

Ok, checked the resistance on the lamp leads and I get for both 0L. Also, c831 and C834 give me 0L and C817 gives me 449ohms.

[will62]

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

Can you flip your meter over to AC and remeasure pins 1,2,3 & 16?

[Dumah Brazorf]

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

Maybe you should use a 10k resistor for the white connection.
Check resistance of your lamps leads and on the blue high voltage caps.

[rddube]

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

I think you read the right side top/bottom instead of bottom/top.
If R804 is dropping 5V it should passing ~0,5A so 2,5W. It should be hot.

You're quite right Dumah, my error. Should look like this, sorry for the error:

Pin 1: 5.54V
Pin 2: 0.136V
Pin 3: 0.136V
Pin 4: 0.092V
Pin 5: 0.0V
Pin 6: 1.207V
Pin 7: 3.58V
Pin 8: 3.91V

Pin 16: 5.54V
Pin 15: 0.0V
Pin 14: 0.0V
Pin 13: 5.88V
Pin 12: 13.3V
Pin 11: 13.01V
Pin 10: 15.22V
Pin 9: 15.19V

[Dumah Brazorf]

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

I think you read the right side top/bottom instead of bottom/top.
If R804 is dropping 5V it should passing ~0,5A so 2,5W. It should be hot.

[rddube]

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

Ok, so I took voltage readings on the MP10091 with all 3 resistors in place:

Pin 1: 5.54V
Pin 2: 0.136V
Pin 3: 0.136V
Pin 4: 0.092V
Pin 5: 0.0V
Pin 6: 1.207V
Pin 7: 3.58V
Pin 8: 3.91V
Pin 9: 5.54V
Pin 10: 0.0V
Pin 11: 0.0V
Pin 12: 5.88V
Pin 13: 13.3V
Pin 14: 13.01V
Pin 15: 15.22V
Pin 16: 15.19V

[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.

[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.

[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

[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

[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.

[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.

[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.

[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

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

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