Acer AL2423W Recapped, backlight works but no display

[PlainBill]

Re: Acer AL2423W Recapped, backlight works but no display

Hmm, I don't have enough experience to judge, but all the voltage regulators are AC 1084 0553AL, but the one closest (U13) to the power board measures significantly lower than the other 2????

Now it is possible that is "normal" for this design.

Yes. These regulators are available in fixed and variable output versions.

The pins are numbered 1, 2, 3 across the bottom. 3 is the input, 2 the output, 1 the adjust. By using a pair of resistors from pin 2 to pin 1, and from pin 1 to ground it is possible to set whatever voltage you want. If you notice the voltages, pin 2 is 1.2 volts higher than pin 1.

PlainBill

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Ok, I've been poking allot at this thing today, not much success tho

I added a serial header to CN3, I posted about it's measured voltages here
When I used a RS232 > RS422/485 level shifter I got only a celcius sign (°) in hyperterminal when I started the monitor with the cable connected...
Adjusting the hyperterminal settings made the one character output change but nothing else than that
The level shifter I am using is made by Sparkfun; http://www.sparkfun.com/commerce/pro...roducts_id=449
Now my assumption is that I am supposed to connect it to GND (obviously) and then to the fourth leg which sends out 5v to VDC (so the middle two legs would be TX and RX)

This turns my level shifter into one mode, if I power it from 3.3v it goes into another mode, so I next connected GND to GND, and VCC to the pin right next to it
But now I got nothing at all, either way I connected the TX/RX cables...

At this stage I found an old post where pedro said he had a service manual for this logic board, so I asked him for it and he sent it to me, thank you very much pedro (It confirmed that my first test with GND on GND and VCC on 5v was correct, so TX and RX indeed are in the middle of the pins...)
This manual informed me that this header is supposed to be connected with a software called gProbe (Genesis Probe)
I found that after asking nicley on a Russian forum
However I get no communication at all in either mode with the serial cable using it

So next I started reading more on the JTAG header (J1)
I have a GQ-4X USB Universal Programmer with the ADP-056 adapter
I am now trying to figure out the pinout of the JTAG header on the board but it is difficult, because the markings on my programmers adapter and the service manual are different...

Here are the voltages I measured against ground with the monitor running:
1: 0
2: 0
3: 3.3v
4: 0
5: 3.3v
6: Infinity

Note that I have simply numbered them left > right in respect to this image taken here of the PCB: https://www.badcaps.net/forum/attach...1&d=1399820346

I think they map like this to my programmer, using a crop from the service manual of the relevant section:


1 > ?
2 > ?
3 > TDO
4 > TDI
5 > TCK
6 > TMS

So yeah, those two question marks would be nice if someone could help me with
On that Russian site was a firmware from this monitor posted, so what I'm going to do is save the firmware I have now as a backup and try flashing that to see what happens...

Finally I've attached some pics, both top and bottom this time...
Also I attached a part of the service manual, when I got the whole thing from pedro I was able to find this one via Google which has only the relevant things listed (part numbers and schematics)

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

Hi, Per!

You are much deeper in knowledge of AL2423W than me with this experience!

I had similar problem with AOC monitor - no display. It had broken LVD connector - when I replaced it, picture appears.
I have one suggestion, dismount bezel from LCD panel electronics and check voltage on pins 28-30. There might be the problem.

dD

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

dondrusco; do you mean the small PCB that connects to the panel directly?

I'm currently trying to follow the troubleshooting guide in the service manual
The voltages for the Mosfets checks out as we already know

Next on the list is the Crystal next to the CPU, it should be 14.318Mhz
Now I don't think my Fluke 113 TRMS meter can read hertz, so I broke out my CHY 17 multimeter
It has two hertz modes, one called Lo and one called Hi (Trig)
Now in both modes I get values that are changing, and in the KHZ range, not MHZ (around 40KHZ)
Now the specs for the meter says this:
"Frequency Ranges: 10 Hz–2 kHz–15 MHz"
In a Chinese manual it mentions this;


Now I wonder if I'm just doing it wrong or have I actually found the culprit?

CHY 17 Manual (Chinese)

[jetadm123]

Re: Acer AL2423W Recapped, backlight works but no display

Hello Per. I think what dondusco is referring to is the same board I described in my earlier post. As an example, I've included a photo of my Viewsonic. It's the board at the top (spanning the width of the monitor) with the plastic cover folded back. I think yours is located under a metal cover.

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

dondrusco; is it the PCB under this shield you mean in the attached picture?
And where do I measure the voltage of the pins, under the PCB (where it connects to the panel?)
What happens if I get dust on the panel, can I just remove it with a lens cleaning tissue for my camera for example?

And what voltages do I expect on these pins?
Are they listed in the service manual?

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

Use diagram 02. SDRAM/AMP/OUTPUT - CN5.

Follow wire colors from PCB to LVD and check voltages there.
I expect problem - pins 26,27, 28 and 30 - 3,3V

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

dondrusco; do you want me to measure on the underside of the LVD board (the board I pictured in the previous post?)
If so it would need to be disconnected from the panel when measuring... If you just want me to measure where the cable connects to the LVD can't I just measure where it goes out from the logic board instead?

That is what I did, I measured at the outputs on the logic board, i.e. connector CN5 on the logic board, also visible in the bottom of the picture in my previous post...

These where the results;
30=4,9v
29=4.9v
28=4.9v
27=0v
26=0v

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

There is no voltage @26 and 27 pins. Check U12 and capacitor C196. +3,3_DVDD line

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

You can also check 3,3_DVDD @ emitors of Q8,Q9,Q10. If there is no voltage, you probably cut the line under C196 during exchange. It is power for keyboard and LEDs, too.

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

U12 = double checked, voltages still same as this post
Pin 1 was slightly lower, but if I understand the schematic right this is a control loop voltage, so it will be different depending on how much load is on the system (how hard U12 is having to work to produce a clean 3.3v output)

C196 = 3.356v

Q10 = Emitter=3.352v, Base=2.602v, Collector=0v
 Q9 = Emitter=3.352v, Base=2.582v, Collector=3.256v
 Q8 = Not installed

These transistors has these markings (the "44" is written 90° in relation to the other text)
R2A 44

I think this is the correct PDF;

I attached a cropped picture of the relevant section, it is also available in full resolution version; https://www.badcaps.net/forum/attach...1&d=1399820456

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Did some further tracing of pins 26 and 27 on CN5 that showed zero volts
Turns out they have been left out of the circuit at installation
R152 & R164 that connect to pin #27 are missing
R150 & R163 that connect to pin #26 are missing

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

OK, I found, that resistors are NC. (in the schema)

You have to trace that grey, magenta and blue wire to the panel board.
There is one SMD fuse just behind LVD to protect panel.

If there is voltage behind the fuse, we have to return back to Genesis chip.
You have to have oscilloscope to detect signals @ data pins of CN5.
If there is no signal - then panel is OK, control chip is probably dead.
Otherwise, the panel is probably dead.

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Hi, I finally managed to get the metal cover off the LVD board
There was one fuse I could identify, F1
It reads 4.9v on both sides to ground...

Actually I am reading ca 0.8 > 1.5v on the data pins of CN5 with my Fluke 113 DMM in manual voltage measuring mode (I do not use auto mode because it is dangerous)

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

The last thing, which comes to me, is reset flash eeprom to default settings.

But I have never done it before...

See https://www.badcaps.net/forum/showpo...71&postcount=7

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Thanks for the link dondrusco, but I'm not having much luck via Google to find similar instructions for my monitor
Do you know where the monitor stores the settings, is it in the SST25LF040A flash chip?

Because I asked for instructions on how to connect my programmer to the JTAG header but seems it is not possible at all
I wonder how the monitor would respond if it's eeprom was corrupt, this is my current theory...

I should mention I have ordered the X1 crystal and the Teapo capacitor for position C147 that I did not have in stock (it sits right on the power line to the panel FYI...)
Btw, the power to the panel, is it supposed to be 4.9 (5v?) I can't seem to find this info in the service manual...

> Hi, I've got a GQ-4X with a ADP-056 adapter
> I would like to read the firmware via JTAG on an Acer AL2423W monitor
> It has a Genesis chip on the logic board, and the EEPROM is a SST25LF040A
>
> I have attached the pinout of the 6-pin header from the service manual,
> how do these map to the ADP-056?
>
> I think I have a few figured out, but not sure;
>
> J1> ADP-056
> 1 > ?
> 2 > ?
> 3 > TDO
> 4 > TDI
> 5 > TCK
> 6 > TMS
>
> Sincerely - Per Hansson

Hi,

Thanks for the email.

The GQ-4X supports CPLD programming via JTAG.

Your chip SST25LF040A is not a JTAG chip, it is a SPI chip.
If yo want to read,write this chip via JTAG connection, then you need a
customized JTAG device. The GQ-4X does not work that way.

If your mother board has a SPI port, then you can try to programming the
chip via SPI port. Otherwise you need to remove the chip from mother board
and programming it on the programmer directly.

Regards.

[ndugu]

Re: Acer AL2423W Recapped, backlight works but no display

In processor GM5861H there is no internal memory of the programs, all program code is stored in SPI Flash SST25LF040. At monitor inclusion look on pinouts 2, 5, 6 microcircuits U8 go an exchange of the information or not. In my case, at power up there was a short-term activity (1-2 seconds), then the activity termination. It says with the big share of probability that the program code is deformed.

--------------------------
В процессоре GM5861H нет внутренней памяти программ, весь программный код хранится в SPI Flash SST25LF040. При включении монитора посмотри на выводах 2, 5, 6 микросхемы U8 идет обмен информации или нет. В моём случае, при влкючении была кратковременная активность (1-2 секунды), затем прекращение активности. Это говорит с большой долей вероятности о том, что искажен код программы.

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Welcome to Badcaps and thank you very much for your post ndugu!
Did you have to use an oscilloscope to measure pins 2, 5 & 6 on U8?

-----------------------
Добро пожаловать в Badcaps, и благодарю Вас за Ваше сообщение ndugu!
Вы должны использовать осциллограф для измерения контакты 2, 5, 6 на U8?

[dondrusco]

Re: Acer AL2423W Recapped, backlight works but no display

говорите немношко по-русски?

Just kidding, - i have typed text above for 5 minutes (@US keyboard layout)

It's interested to see step by step solving this issue.
Good luck!

[Per Hansson]

Re: Acer AL2423W Recapped, backlight works but no display

Here are my readings with multimeter;

#1, CE = Short blip at a volt or so then 0v
#2, SO = 3.325v
#3, WP = 0.971v
#4, VSS = GND
#5, SI = 3.313v
#6, SCK = Short blip at a volt or so then 0v
#7, HOLD = 0.967v
#8, VCC = 3.354v