Benq G2255 doesn't power on - amber power light when plugged in - part 2

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Ok, so bad news, the original flash chip is identical to the .bin file I had downloaded and there is a verification option of the chip and it reports perfect.

I programmed some of the new chips (left the original intact) and all chip contents are the same.

So the problem lies elsewhere.......

I think I found the EEprom file on a Russian website 2k bytes long.

http://monitor.espec.ws/section33/topic250038.html

Should I check the Eeprom see if it compares?

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Well, that is bad news. You might as well check the eeprom. If all is well there, it may go back to the low ohms to ground on your 1.8V/3.3V.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Ok Will, so here's the scoop. I checked the Eeprom and read the file and saved it. Compared it to the one I downloaded, and although it starts the same, the rest is almost all different...many many differences.

So either the eeprom file I downloaded is not the same version (although the flash file was the same) or my eeprom is corrupt?

What do you think I should do? I am attaching a copy of both files (my eeprom file and the one I downloaded) in zip format because I can't upload a .bin file.

I checked my eeprom chip and I get the following message: "Chip main memory and buffer same", whatever that means!

Attached is a comparison of both files.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

I can't make anything out of the differences. I did notice that the new file is almost twice the size of the old one. Do you have one of those "24" eeprom chips (sufficient size) on another board, that you could pull and copy the new file to? Until you know more, I wouldn't erase what is on that eeprom.

edit:
Ok, got both open in Visual Studio. The new one is not twice as large, but is larger. Did you notice that some of the 16 Bytes of data are the same, just at different addresses? They both also skip down to about 600 and pick up with more data. There's nothing here that I can see that changes what I said above.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Ok, found a 24C16WP from a scrap board - erased it and put the other eeprom file on it. Need to resolder the flash and the new eeprom and give it a try. I'll try and do this tonight, however the movers came in today for my basement water damage and everything is upside down, including my opened monitor that I had stashed away during the construction work. Will keep you posted.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Did the test with the new eeprom and still same result, as power is applied the amber light comes on and the switches have no effect. So not flash and not eeprom. Should we go for the big TSU ??

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Looking at the main board and taking readings here and there and I found 2 caps that I get a 15 ohm measure, photo attached.

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

I need to look back on the circuit, but those look like filter caps for the 5V to the t-con. We didn't have low ohms to ground on the 5V line, did we?

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

No, on the 5V rail I get 575K ohms rising.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Hey Will, when you have a chance take a look at this Russian thread. One guy says he changed the "prots" (translation) and seems to go on and say he changed the TSU and it fixed it.

http://**************/forum/54-31467-1#283782

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

It will only let me read the first few posts w/o logging in, and I don't want to register for 1 post. Can you paste the translation of the post that discussed the resolution to the problem?


Edit: Added diagram for panel_on and lcd_5V_aware

You can remove those caps with low resistance to ground to verify, but I'll bet the low value is from the TSUM chip lcd_5V_aware. Follow attached circuit.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Here you go, the whole post. Towards the end there is a user called DDD that talks about prots ?

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Kind of a rough translation, but the way I read it, is that he had seen another monitor with the same issue, and fixed it by replacing the TSUM chip. He substituted an NHJ for the NWHJ version of the chip.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Yes, that is kind of what I thought too. Well I ordered a TSUM chip on Aliexpress....I guess that looks like the next logical step?

[will62]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

I think that's the best move. You going to practice your drag soldering on a scrap board?

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Hi Will. I already did and am getting pretty good at it....I unsoldered and soldered back a Winbond chip that is pretty much the size of the TSUM. My only concern is when I remove the TSUM, there are very little ceramic capacitors right beside it that my blow away!

I bought aluminum tape and am going to mask around the TSUM when the time comes.... I'll keep you posted in about 3-4 weeks'

[nomoresonys]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Cool thread, very interesting, I hope you guys solve it.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

I have 2 boards (scrap boards) that come from a Dell E207wfp, copy of service manual attached.

The main chip looks like the same footprint as the TSUM, but I can't identify which chip it is as it has a heatsink solidly glued to it, that might damage it if I try and remove it.

The board is a 715g2089-1 and in the schematic in the manual, they say U401 which corresponds but don't say what chip it is. How can I find out if it is a TSUM or not?

If it was, I could do my test immediately.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Cool thread, very interesting, I hope you guys solve it.

Thank you. Actually Will62 is the brain behind this and I am the executor. Without Will62 wouldn't have gotten this far. I have learnt a lot doing this.

Don't forget there is a part 1 to this thread where I think we solved the power board inverter problem. This thread is about the main board.

[rddube]

Re: Benq G2255 doesn't power on - amber power light when plugged in - part 2

Ok, I succeeded in getting the heatsink off and even though the glue is still there, I think it is a GM5766 (I only see the beginning GM57...so I assume that is what it is.

Don't suppose it could be a replacement for the TSUM? Copy of the datasheet attached.