| Hello amazing geniuses, boy do i have an exciting machine with me that needs knowledge I don't posses. Alright so machine was liquid damaged top case side. The board only seemed to have liquid on the backlight decoupling caps. So shorted to ground. So I removed the caps to find a crater. Still had a short to ground on ppvout_lcdbcklt, so I injected voltage and internal short near cp601 and cp604. Then proceeded to dig the short out, lots of grinding and cutting later the short is gone. Yay! However, this was shorted lived as still no backlight. Now the confusing stuff. I have backlight output essentially 51 v on ppvout_lcdbcklt which to me seems like the lcd panel isn't being told to accept the backlight. The screen in question is fine, tested with another board. Also don’t have keyboard backlight if that helps. I have replaced up800 no change. one thing to note i only get about 19mv on up800 pin 4, while comparing with another machine it gets 0.8v. also the i2c data lines are 5.12v Let’s solve this mystery together. I would have loved to show pictures but my old microscope gave out and the sd card failed with it. I will do my best to provide pictures going forward. |
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A2337/820-02016 No backlight
- Thread starter DDVL
- Start date
First of all, welcome to the forum.
Check continuity from K/DP800 to pin 43/JP600.
Pin 4/UP800 voltage is not relevant; its voltage depends by the PWM signal achieved.
The actual duty cycle is very low (no load) and also DC voltage measured by voltmeter.
Be sure the video cable between MLB and T-CON is good; try known good one, if possible.
You've mentioned missing KB backlight.
It may be caused by non working ALS; is the camera working?
Check LP670 and UP700 output voltages.
Check continuity from K/DP800 to pin 43/JP600.
Pin 4/UP800 voltage is not relevant; its voltage depends by the PWM signal achieved.
The actual duty cycle is very low (no load) and also DC voltage measured by voltmeter.
Be sure the video cable between MLB and T-CON is good; try known good one, if possible.
You've mentioned missing KB backlight.
It may be caused by non working ALS; is the camera working?
Check LP670 and UP700 output voltages.
Thank you for the warm welcome.
Regarding k/dp800 i used 1/cp873 to check continuity. I assumed it would be ok as its the same line when i last checked.
I am about 90% the t-con is good but will check with another one later.
I also thought ALS might be an issue so i had checked lp670 and have 5 volts on both sides.
UP 700 seems good as well.
Regarding the camera not working i am unsure however when i power the screen with a different board it has backlight. Also I tried a different screen to check but no change.
What's next?
also lid open voltage is 1.8
Regarding k/dp800 i used 1/cp873 to check continuity. I assumed it would be ok as its the same line when i last checked.
I am about 90% the t-con is good but will check with another one later.
I also thought ALS might be an issue so i had checked lp670 and have 5 volts on both sides.
UP 700 seems good as well.
Regarding the camera not working i am unsure however when i power the screen with a different board it has backlight. Also I tried a different screen to check but no change.
What's next?
also lid open voltage is 1.8
Camera and ALS are powered from the same line.
I asked about camera, in case of missing power.
Just check if ALS works properly.
ALS problems may be caused by MLB bad circuitry; not only by LCD assembly.
I asked about camera, in case of missing power.
Just check if ALS works properly.
ALS problems may be caused by MLB bad circuitry; not only by LCD assembly.
How would you like me to test that? When i use the other motherboard the screen does light up. I did put the board in a different assembly but same result. I also believe als on motherboard side is at fault but have no idea what else to check. I did change the lcd cable with a known good one but the result was the same.
I was also able to recover a picture of the damage.
But it seems the image is too large to add.
I was also able to recover a picture of the damage.
But it seems the image is too large to add.
Use external monitor, but keep internal LCD connected.
Keyboard backlight adjust is disabled?
Should test that keyboard with good board also (if possible).
Keyboard backlight works when you connect the LCD assembly to other chassis?
Upload the picture somewhere else and post only the link here.
Are you sure didn't destroy other traces when you eliminated the short from the board?
Lost communication between JP600 and UP800 (I2C bus) can cause this problem.
Keyboard backlight adjust is disabled?
Should test that keyboard with good board also (if possible).
Keyboard backlight works when you connect the LCD assembly to other chassis?
Upload the picture somewhere else and post only the link here.
Are you sure didn't destroy other traces when you eliminated the short from the board?
Lost communication between JP600 and UP800 (I2C bus) can cause this problem.
Ok so i haven't tried connecting to an external monitor just yet. I will do that and get back to you regarding it.
I don't think i destroyed any data lines. As the short was on the decoupling capacitors. So here is the link to the picture
drive.google.com
I don't think i destroyed any data lines. As the short was on the decoupling capacitors. So here is the link to the picture
20230331_172103.jpg
drive.google.com
I recommend you to confirm continuity from DP800 to JP600.
You've carved the board on the backlight output.
Are you sure the trace is still good all the way?
You've carved the board on the backlight output.
Are you sure the trace is still good all the way?
That's good.
You should check continuity with corresponding point on the T-CON; to discard connector problem.
Also check continuity between JP600 and RP850/51.
Be sure all RP850-53 are good, as traces too.
Do the same for JP600 and UD050.
You should check continuity with corresponding point on the T-CON; to discard connector problem.
Also check continuity between JP600 and RP850/51.
Be sure all RP850-53 are good, as traces too.
Do the same for JP600 and UD050.
Ok so ud050 pin 5 and jp600 pin 20 no continuity.
Diode mode with red to grouund -
Rd053-2 --> 0.079
Rd053-1 --> 0.539
Rd051-2 --> 0.005
Rd051-1 -->0.281
Resistances -
Rd053 - 1.78k
Rd051 - 1.39k
Normally i would take of ud050 check diode mode and see what happens and then if readings normal replace it. What do you suggest to do?
Diode mode with red to grouund -
Rd053-2 --> 0.079
Rd053-1 --> 0.539
Rd051-2 --> 0.005
Rd051-1 -->0.281
Resistances -
Rd053 - 1.78k
Rd051 - 1.39k
Normally i would take of ud050 check diode mode and see what happens and then if readings normal replace it. What do you suggest to do?
You should fix the trace between JP600 and UD050.
"Rd051-2 --> 0.005"
That may be a big problem.
If UD050 is not causing such a low value, then M1 is damaged.
I hope you've wanted to say RD052 instead...
"Rd053-2 --> 0.079"
This looks also low.
If get that value without LCD connected, then UD050 is probably bad.
Can you compare with good board?
"Rd051-2 --> 0.005"
That may be a big problem.
If UD050 is not causing such a low value, then M1 is damaged.
I hope you've wanted to say RD052 instead...
"Rd053-2 --> 0.079"
This looks also low.
If get that value without LCD connected, then UD050 is probably bad.
Can you compare with good board?
Well i guess this board is done.
Removed ud050
Rd053 -2 --> 1.7v without ud050
Rd053-2 --> 0.6 on a good board
The bad rd051-2 --> 0.005 even after removing ud050
Rd051-2 --> 0.369 on a good board.
Is it safe to assume the board is fucked?
I shouldn't bother with attempting to fix any traces on jp600?
Removed ud050
Rd053 -2 --> 1.7v without ud050
Rd053-2 --> 0.6 on a good board
The bad rd051-2 --> 0.005 even after removing ud050
Rd051-2 --> 0.369 on a good board.
Is it safe to assume the board is fucked?
I shouldn't bother with attempting to fix any traces on jp600?
The M1 can't control backlight anymore.
You can't bypass anything on video connector.
Backlight is adjusted through I2C bus by M1.
UD050 is a level shifter between M1 (1.25V side) and T-CON (3.3V side).
Use quality flux and heat M1 in case of accumulated crap underneath.
Look at boardview and apply heat especially on the area where this bus connects to M1.
You can't bypass anything on video connector.
Backlight is adjusted through I2C bus by M1.
UD050 is a level shifter between M1 (1.25V side) and T-CON (3.3V side).
Use quality flux and heat M1 in case of accumulated crap underneath.
Look at boardview and apply heat especially on the area where this bus connects to M1.
You don't need to melt the balls.
Is supposed to burn eventually accumulated crap only.
Is supposed to burn eventually accumulated crap only.
Do i remove the silicon that holds the m1 in place? So essentially just heat it up to 450 mainly in the area that affects the backlight or the entire m1 chip?
If that potentially works i gotta run jumpers for the jp600 connector right?
I don't know if you can tell but i am actually fairly new to fixing motherboards. The biggest bga i ever touched was a cd chip. Also i don't know what temp flux would boil at or remove crap from soder joints. So this information would be helpful.
If that potentially works i gotta run jumpers for the jp600 connector right?
I don't know if you can tell but i am actually fairly new to fixing motherboards. The biggest bga i ever touched was a cd chip. Also i don't know what temp flux would boil at or remove crap from soder joints. So this information would be helpful.
Last edited:
If M1 is completely surrounded with glue, there is low chance to have any crap underneath.
I gave you this idea as last resort.
150-200 degrees (on MLB) for 15-20s should be good enough.
The real settings on the hot air station depends by model, distance to MLB.
If you aare not sure what to do, may be better to leave it as is; if still can be used with external monitor.
Recover data before any try, if needed.
I gave you this idea as last resort.
150-200 degrees (on MLB) for 15-20s should be good enough.
The real settings on the hot air station depends by model, distance to MLB.
If you aare not sure what to do, may be better to leave it as is; if still can be used with external monitor.
Recover data before any try, if needed.