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

[rddube]

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

Ok, here is the first tests.

What measure pin 1 and 16 in this case?

Dumah, you are going to see what I get on pin 1 and 16 in the photos.

For Will:

Lights come on nice and solid, no flickering no tint, just white light top and bottom.

First I show you my setup, so you can admire

Next are the photos for pin 1, then pin 2, 3 and 16 respectively. 1, 2 and 16 look smooth, but pin 3 is pretty spiky. I took 2 photos of pin 3 so you could see the amplitude, especially on photo 2.

So what next, do I next, do I flip the board and do the tests, or is there something wrong with pin 3?

Tks a million!

[Dumah Brazorf]

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

Swap the lamps. If pin2 became spiky and pin3 smooth there's something wrong with a lamp.

[rddube]

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

Swap the lamps. If pin2 became spiky and pin3 smooth there's something wrong with a lamp.

Ok Dumah, will do the tests this afternoon as I have to flip around and reinstall my alligator clip on C803 to short pin 5. Right now I have to go get my grand daughters to bring them to Toys'r us, order from my wife!

Will probably wait for Will's advice too. Since pin 3 is current feedback for one of the lamps, could it not be a component on the line from the lamp to pin 3 that could be causing this? We'll know for sure once I do the test.

Thanks for your advice.

[rddube]

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

Ok, here is the first tests.



Dumah, you are going to see what I get on pin 1 and 16 in the photos.

For Will:

Lights come on nice and solid, no flickering no tint, just white light top and bottom.

First I show you my setup, so you can admire

Next are the photos for pin 1, then pin 2, 3 and 16 respectively. 1, 2 and 16 look smooth, but pin 3 is pretty spiky. I took 2 photos of pin 3 so you could see the amplitude, especially on photo 2.

So what next, do I next, do I flip the board and do the tests, or is there something wrong with pin 3?

Tks a million!

Sorry gentlement, while setting up to do the test with the CFL's plugged in the opposite sockets, I realized that the tests above were done on pins 2, 3, 4 and 16...not pin 1. So the photos are for pins 2, 3 and 4 instead of 1, 2, 3.

I tried repeating the test this time with the CFL's the other way, this time on the right 1, 2, 3, pins, but for some reason my oscilloscope doesn't show me a stable sine wave, it jumps all over the screen - same thing for all 3 pins. There must be something I am doing wrong? The CFL's light up as before however. Will try again and see what gives. Sorry for the error in the previous post.

[will62]

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

Well, I posted some things to check next, before reading your comment above. I've edited all out except asking for a new pic. Hopefully you get some stable waves with lamps swapped. If not, go back to original setup and probe pin 1. I think that's all we're missing. Rename pics with correct pin #'s.

Can you take a complete pic with light under the board, similar to the ones you put up earlier?

[rddube]

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

Ok, found my problem with the waves jumping...this oscilloscope has alligator clips so the ground is fine, but the probing wand I had to make out of a copper wire (solid) and I was holding the wire instead of the plastic covering the alligator clip, creating disturbance I guess.

Here are the real pins 1, 2, 3 and 16, with the CFL's connected as original. I noticed that I have a hold function on the oscilloscope so I used it to take the pictures, hope that's ok.

Will get to redo pin 1 with other setup, will rename the photos and reupload everything including a photo of the whole board with light under, right after lunch.

[rddube]

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

ok, redid all the tests CFL's inverted and CFL's in their original position and here are the photos of the scope.

I noticed pin 16 was changing frequency quite a bit, so I took a little video (hope it's ok to post it here, if not I will remove it no problem - had to put it in a zip file because the extension is not allowed) to show the movement of the wave.

[will62]

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

Good job on the pics and video. Those voltages (min,max,pp) are all over the place, and not following the lamps to different connections. The waves also don't look like what is expected based on the datasheet (pic on post#114). Note that the "LI" waves center on 0V and the "OV" waves center on 6V. Keep in mind that we don't have the datasheet for MP10091ES. I am looking at the datasheet for MP1009. I have seen specs that refer to the 10091 as being from the 1009 series, but we already know they have different pin-outs, and they probably also have different internal parameters.

I wonder if some of the wave changes are related to when they were measured. We know that the chip is seeing something that it doesn't like in the first couple of seconds. Just to be sure, Can you please redo the tests, but start each test from power being off. Try to press hold as quickly as possible on each test. No need to take new pics, just give me min, max & pp for each pin at startup. If pin 16 is doing what you show in the video, I don't doubt that it is causing the shutdown. There's a couple of ways to check that, and we'll try those next.

[rddube]

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

Ok, here are the readings for pins 1, 2, 4 and 16 (I also jotted down the frequency):

Frequency Min Max PP

Pin1: 59.19Khz -37.58V 5.23V 42.52V
Pin2: 71.49Khz -37.58V 6.64V 44.23V
Pin3: 71.036Khz -37.58V 7.85V 45.44V
Pin16: 71.78Khz -37.58V 3.22V 42.81V

Hope these make sense. I put power on and as quickly as possible pressed the hold button on the scope.

[rddube]

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

Will, this pinout seems to be the one of the MP10091ES, taken from a Philips service manual attached. The critical components for IC801 is an MP10091ES.

[rddube]

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

Ok, here is a photo of the whole board with lights shining under it.

[will62]

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

Yes, the diagram of the MP10091ES that I put the voltages on, came from a Philips SM, maybe the same one you attached above. Problem is that we don't have the datasheet for the chip. Parameters could be different, so waves on pins 16, 1, 2 & 3 could also look different.

This is going to be tedious, but I think that it is necessary to move forward. Let's lift 2 pins at a time, so we can narrow down the connector that the problem is coming from. But, when you lift a pin, the chip is not going to be happy with no input, so you'll have to use a jumper to "borrow" the input from the other pin. The OV1(p16) and LI1(p2) go to connector 801. The OV2 and LI2 go to connector 802. So, to start:

Lift pin 16, jumper from pin 1 to lifted pin 16.
Lift pin 2, jumper from pin 3 to lifted pin 2. (jumper can be solder bridge on 2&3)

Now you have voltage and current monitoring from connector 801 removed. Remove the pin 5 jumper and power up. Do lights come on? If not, resolder pins, and lift pins 1 and 3 (jumpers stay, and they need to go to lifted pin, not it's pad). Power up again, any change?

Thanks for the pic, really clears some things up.

[rddube]

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

Ok, Will, did the first test Lift Pin 16 jumper from pin 1 to lifted pin 16. Lift pin 2, jumper from pin 3 to lifted pin 2. Removed jumper on pin 5, put power and the lights come on and stay on.

I had the lights plugged the inverted way, as I wanted to have the power board upside down so as to not touch my jumpers. So the problem would be connector 801?

[will62]

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

Now try inverting the connectors. Light still come on? If not, we have a lamp or connector problem. If yes, we have a connector 801 circuit problem.

I think that it is an over voltage reading on pin 16. Resolder pin 2 and remove jumper between 2&3. Try powering up again. If lights come on, we don't have a current monitoring problem. We can focus on the components that are used to measure the voltages.

[rddube]

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

Inverting connectors, both lights come on and stay on.

I am trying to see how this relates to the connector 801 circuit...can you trace it on the photo for me to understand?

Tks Will, you are a genius!!

Will have to remove the board to do the second test (i.e. resolder pin 2 and remove jumper between 2&3 (I presume I leave the jumper on 1 and 16?). Will get back to you in a few minutes.

[will62]

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

Yes, leave jumper on 16 & 1. Once we narrow it down, I'll try to explain what I think is happening.

[rddube]

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

ok, with jumper 2 to 3 off, pin 2 soldered down, the lights turn on for a few seconds (2 seconds) and turn off.

[will62]

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

Well, that shot my over-voltage theory to heck. Now, we need to confirm if it is an over-current problem. You'll have to resolder pin 16 and remove 1-16 jumper. Re-lift pin 2 and replace 2-3 jumper. If light comes on now, we have a current problem. If not, we have a problem with a common component between voltage and current monitoring.

[rddube]

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

The lights come on and stay on with the 2-3 jumper (pin 2 lifted) and the 1-16 removed and pin 16 resoldered. What do we have to check?

[will62]

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

OK, the chip is shutting down due to an over-current reading on the connector 801 circuit. I haven't had a chance to go over the updated under lighted pic yet. It may be sometime tomorrow before I have a chance to get back to you. In the mean time, cold solder joints are sometimes hard to see. You might start at transformer secondary pin 7 and resolder every through-hole component from there down to and around cn801 (including cn801).

We know where the problem is now, so you can resolder pins and remove jumpers.