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

We use the resistors to simulate the control signals of the main board, this is how you test the power supply board by itself.

Could it be that if the supply board has a problem it would be why the whole thing doesn't start, just the amber power light that comes on?

Any ideas what I should check next? I checked for the +17V (in the schematics), the +5V and +3.3V and they are all present.

[budm]

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

https://www.badcaps.net/forum/attach...4&d=1515532125
The 8-pin SMD device on the right is the dual power MOSFET for driving the Inverter transformer.
I wonder if you are getting the 12~18V on the Cap 801 to run the inverter circuit or not.

[rddube]

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

Budm, on Cap 801 I am getting 20.4V.

[budm]

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

OK, so the inverter section is getting the 20VDC to run but it is not running at this point, more in-depth troubleshooting needed.

[rddube]

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

I am open to any suggestions and will try anything you think could lead us to the culprit

[budm]

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

Look up the P/N of the IC801 to get the spec sheet so you can probe the VCC pin and the Enable pin to see what you have.
Might as well get the P/N and the spec sheet of the MOSFET too.

[rddube]

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

Look up the P/N of the IC801 to get the spec sheet so you can probe the VCC pin and the Enable pin to see what you have.

Ok, got the spec sheet for IC801, but not sure how to read it. Can you help me Budm and tell me what voltages I should expect on a particular pin? I can see where pin 1 is and measure voltages, but I am not sure what I should expect.

Might as well get the P/N and the spec sheet of the MOSFET too.

Got that too, and it is attached - again by reading the spec sheet, not sure how that one works, although it looks to be more simple than IC801.

Also, when doing the voltage readings on these chips, should they be done with the resistors in place - if so could you just confirm which wires I should jump again to the 5 volt? Tks!!

[budm]

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

You will leave all 3 resistors in place while testing the power supply/inverter board by itself, isn't that what you have done so far?
I will have to look at the spec sheet first to study the pin out of the IC.

[rddube]

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

No, I only had 2 resistors at a time, once the way you had mentioned to put them and the other time the way Dumah had said to try. Should I have 3 resistors i.e. the blue, white and green to 5V ?

Also Budm, did you see the photo in post #20, one of the heated areas is right under the mosfet...could that mosfet be bad? I have some AF4910N rated at 30V (the one there is rated at 40V) that I could try and substitute.

[will62]

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

Hello Rddube,
I've been following your progress on this BenQ. I'm adding a couple of pics that may help you until Budm gets back to you. The schematic is for a different model, but uses same/similar driver chip and dual mosfet. Hopefully it will help you follow how this chip handles fault detection.

[budm]

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

https://www.badcaps.net/forum/attach...8&d=1515615274
Check the DC Voltage on pin 9, 4, and 13.
All the resistors (1K) are still connected in place.

[rddube]

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

Thanks Will. Ok Budm, here are the results of my measurements with all 3 resistors connected:

Pin 4 = .092V
Pin 9 = 15.5V
Pin 13 = 5.3V

I also found this schematic which seems to be very close to the one I have, attached.

[budm]

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

Thanks Will. Ok Budm, here are the results of my measurements with all 3 resistors connected:

Pin 4 = .092V
Pin 9 = 15.5V
Pin 13 = 5.3V

I also found this schematic which seems to be very close to the one I have, attached.

You are not getting the Enable signal on pin 4, it should be >2VDC.
EN Function
The MP1009 has integrated EN function with
the feedback compensation pin COMP. A logic
low (typical below 0.5V) turns off the IC. An
open collector (OC) si gnal is req uired as EN
signal which connected to COMP.
Can we see pictures of the board showing us how you have the resistors connected?

[rddube]

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

Here you go for the resistors. It might look as if the wires are touching each other in the photo, but don't worry they are not when I am under test.

I then traced the circuit that goes from the connector and feeds that pin 4, photo attached with voltage readings along the circuit. At resistor R802 is where the voltage drops. R802 is a 304 resistor, so 300K, I was getting a reading in the megahoms. So I changed that resistor thinking it was open with a good 304 smd resistor. I now get 30K reading in ohms and when I apply voltage, I still get .09V on the left side of the resistor???

So then I thought C805 might be the problem so I unsoldered it and tested it out of circuit 239pf, ESR 2.9, and without it soldered I still get 30K reading on the resistor, so I just resoldered back the capacitor. Tested the voltages again a second time to make sure, and I get what is in the picture???

[rddube]

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

Hello Rddube,
I've been following your progress on this BenQ. I'm adding a couple of pics that may help you until Budm gets back to you. The schematic is for a different model, but uses same/similar driver chip and dual mosfet. Hopefully it will help you follow how this chip handles fault detection.

Hi Will62,

Yes the schematic seems very close to my model, in fact I have another one that I posted earlier that I thought was the right one, but they all have some differences.

Trying to figure out why I get a voltage drop on the resistor mentioned in the post just before that I point to in the photo.

[will62]

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

The MP1009 chip internally pulls the enable pin to ground if a current/voltage fault with the lamps is detected. The fault detection delay time for this chip is 220us. That is far too fast for you to capture changes with an RMS meter. Even a good meter with peak/max function requires ~250us to register. If you have a meter with the max function, could you go back to post #30 and try what is detailed in pic#2?

[budm]

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

For the lamp detector error to work, the lamps has to fire up first hen the error detection will kick in if the the lamps fail (only takes one bad lamp for the shutdown to happen) to conduct (or open circuit, I.E. no lamp connect) after firing Voltage is applied to the lamp, but since the lamps never did flash (I doubt that both lamps are bad) on for seconds. The circuit also has over current protection.

[budm]

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

Here you go for the resistors. It might look as if the wires are touching each other in the photo, but don't worry they are not when I am under test.

I then traced the circuit that goes from the connector and feeds that pin 4, photo attached with voltage readings along the circuit. At resistor R802 is where the voltage drops. R802 is a 304 resistor, so 300K, I was getting a reading in the megahoms. So I changed that resistor thinking it was open with a good 304 smd resistor. I now get 30K reading in ohms and when I apply voltage, I still get .09V on the left side of the resistor???

So then I thought C805 might be the problem so I unsoldered it and tested it out of circuit 239pf, ESR 2.9, and without it soldered I still get 30K reading on the resistor, so I just resoldered back the capacitor. Tested the voltages again a second time to make sure, and I get what is in the picture???

So what Voltage do you get on each end of the those 3 resistors (not the end that connected to the 5V)?

[budm]

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

https://www.badcaps.net/forum/attach...9&d=1515615274
https://www.badcaps.net/forum/attach...6&d=1515675227

" At resistor R802 is where the voltage drops. R802 is a 304 resistor, so 300K, I was getting a reading in the megahoms. So I changed that resistor thinking it was open with a good 304 smd resistor. I now get 30K reading in ohms and when I apply voltage, I still get .09V on the left side of the resistor???"
BTW, that point in the picture that you show .09V on the left side of R802 and the other test point you show is CIRCUIT GND!
What do you actually get at pin 4?
BTW, the picture is not super clear for me to trace the circuits in real details so I am not sure if the traces for pin 7 (BOSC) and pin 8 (DBRIGHT) I marked are correct or not.
Need to verify if the right side of R802 (left side of R802 is connected to GND) is connected to pin 7 of the IC or not.
The circuit looks to be about the same as shown in the spec sheet of the IC.
I can see EN pin 4 connected to cap C802 (another end of the cap is connected to GND) but I cannot see where else pin 4 goes to in the picture.
Also you show one of the control line has 3.9V, what is the Voltage of the other control line?

[rddube]

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

Good evening gentlement.....didn't have time to do the tests tonight, but I did take a closer picture of the chip and surroundings. The other side of R802 seems to be connected with the cap that goes to pin 4?

The voltage I get on pin 4 is .092V, so if that is ground where does pin 4 get it's voltage from?

Anyhow, I will do the tests that you asked Budm (and will do the test that Will62 suggested) and report on my findings very shortly. Thank you for your patience.