Asus VW246H will not power on

[momaka]

Re: Asus VW246H will not power on

Hi Jan and welcome to the forums!

It came out that when I heat up the main board the everything worked again. Due to that I would say there is a cold solder point on the main board. I checked the board visually, but I cannot identify anything "abnormal" (To be honest I am noob).

Do you agree that it must be cold solder joint or could also be something different?

It could be a colder solder joint, indeed. However, I am more inclined to think the issue is related to bad electrolytic capacitors. In particular, I see what appears to be two voltage regulators at the upper-right corner of the board shown in this picture:
https://www.badcaps.net/forum/attach...1&d=1610274625
If you look carefully, you can see that the PCB around and under them has become darker, likely due to the regulators running hot. This doesn't mean the regulators are bad. Linear regulators do tend to run hot, so this could be normal. However, the heat from these regulators can (and often does) make cheaper / inferior quality electrolytic caps go bad over time.

The two small green caps (looks like Lelon or Ltec brand) close to those regulators likely filter power from the regulators. So my suggestion is to start by removing those two capacitors and checking their ESR - if you have a capacitor meter, that is. If not, just replace them. While at it, you may also want to replace the other electrolytic caps on the logic board too, as they could be starting to fail too.

When replacing electrolytic capacitors, make sure to use a good quality brand and low impedance / ESR. For an application like this on the logic board, ESR/impedance is not too important, so anything from "entry-level" to "very low" ESR should be OK.

Here is a list of capacitors suitable for power supplies and generally all monitor applications:
Manufacturer................................Series
Nichicon ................................ PW, PM, PS, PJ, PV, HE, HD, HV, HW
United Chemicon (UCC) ............ KY, KYA, KYB, KZE, LXV, LXY, LXZ, KZH, KZN
Panasonic .............................. FC, FK, FR, FM, FS
Rubycon ................................ YXJ, YXG, YXF, YXM, ZL, ZLJ, ZLK, LZQ

Last but not least, post a picture of your power supply board, if possible.
Even if the power supply board is not causing a problem at this point, chances are it probably has cheap electrolytic cap brands on it as well (not all monitors come with cheap caps, but many do.) Thus, if you are buying caps for the main/logic board already, the cost of getting a few more caps for the power supply may be worthwhile guarantee that you won't have any problems there down the road too.

[jpbnd]

Re: Asus VW246H will not power on

Sorry for my bad grammar. I wanted to correct some mistakes, but I cannot edit. :-)

[jpbnd]

Re: Asus VW246H will not power on

Hello Guys from Germany! I have the problem that my VW246H will not power on. I used a hair dryer to heat it up a little but and it worked! Afterwards it put outside (0° degrees) for 20 minutes and then it didn't work. If I understood correctly correctly this means there is a cold solder joint on the boards.

To locate the part where the heat has an effect I decided to heat the parts separately (Plate with buttons, main board, power supply). The procedure was to remove one item, heat it up, install it and try it again. It came out that when I heat up the main board the everything worked again. Due to that I would say there is a cold solder point on the main board. I checked the board visually, but I cannot identify anything "abnormal" (To be honest I am noob).

Do you agree that it must be cold solder joint or could also be something different? Would it make sense to renew all the solder joints on the backside of the MB?

Regards
Jan

[swofra]

Re: Asus VW246H will not power on

Does anybody have ideas on what could be wrong or what the next step should be? Thank you, any assistance is much appreciated.

[swofra]

Re: Asus VW246H will not power on

so if showing steady 5v at pin 1, is there anything else circuitboard based / other voltages it could be?

[swofra]

Re: Asus VW246H will not power on

5VDC showing at pin 1 on LVDS - with and without the ribbon cable attached to monitor and with the monitor attached to computer. Screen still full white. Power comes on and stay on.

[budm]

Re: Asus VW246H will not power on

So LCD screen connected or not you see the same all white screen, correct? If that is the case, the integrated T-CON on the LCD panel may be be getting the Voltage for Logic board to run.
https://www.badcaps.net/forum/attach...6&d=1577135961
Do you see the Triangle marking on the LVDS connector for pin 1 marking? Check that pin when turn on the monitor to see if what DCV you have on that pin.

[swofra]

Re: Asus VW246H will not power on

It did for a while but now it does not. Regardless, Anytime it was on it was the same all white screen

[budm]

Re: Asus VW246H will not power on

"I completely hooked up the rest of the monitor and had power on the logic board and the standby board. However, the monitor would only come on with a complete white screen flash twice and then go back to standby"

Does it stay on if the ribbon cable to the LCD panel not connected and the monitor is also connected to the running PC?

https://www.badcaps.net/forum/attach...9&d=1598068094

[swofra]

Re: Asus VW246H will not power on

Here are photos as best as I can get. I had to disassemble to get the photos.
To see the other sides of the boards I had to disconnect the pcb/panel ribbon from the screen. The pic with a red circle on identifying the PCB/screen ribbon where it is normally attached when fully assembled. The 4 inverter lights on the right side of the board are also normally plugged in but you can't see those on that view of the boards either. Hope this is close to what you wanted. oh, and don't worry, I have anti static measures and only placed on carpet because it was the best lighting. Thanks again!!

[budm]

Re: Asus VW246H will not power on

So the 3.3V on the logic board is steady, correct?
Can I see how all the boards and screen are connected together?

[swofra]

Re: Asus VW246H will not power on

I already checked that and its good. Sorry should have mentioned that earlier

[budm]

Re: Asus VW246H will not power on

Please read post #51 and #53 about Voltage regulator on the logic/main board.
https://www.badcaps.net/forum/attach...6&d=1577135961

[swofra]

Re: Asus VW246H will not power on

Partial success! Thank you so much! I swapped a 47uF 100v into C606 and immediately had roughly 19VDC between JW20 and JW17. How did you figure out the startup Cap was C606 and had something to do with JW20/JW17? I completely hooked up the rest of the monitor and had power on the logic board and the standby board. However, the monitor would only come on with a complete white screen flash twice and then go back to standby. I took VDC readings on the logic board connector receptacle from the power board and to the monitor control panel from the logic board. Not sure how to tell which power terminal does what but they either all read 5-5.4V, 3.3V, some low mv...except one on the logic board terminal heading to the standby board that reads 4.47 VDC

[budm]

Re: Asus VW246H will not power on

Firstly, hope your dental surgery went splendidly, or as splendidly as something like that could go.
I plugged in the board to a GFCI without it connected to the logic board (logic board cable still attached to power board but its not to logic board - hope that doesn't matter).
Tested the VDC between the output terminals of the bridge rectifier and got 160VDC to verify my meter and power connection was working.
I tested the VDC between GND JW20 and Point A JW17 by putting one probe on each. I tried reversing the probes as well and also tried doing it on the green side by touching a probe to one of the solder points on JW20 and using the other probe to touch one of the solder points on JW17. All tests showed -0 VDC after about 2-3 seconds. i would imagine that would mean there is zero power between the two.

I take it from your suggestion that not getting any VDC somehow means that C606 could be bad and I should replace it? I will look to see if I have any 22 ~47uF 25VDC caps on old boards I've saved, if not, is your recommendation to order one? Looking at that cap, it says 47 uF 50V, do I need to match that exactly?

Thanks again!

My surgery got cancel due to complication so it will be next Tuesday instead.
Just try the caps that have just for testing just to see if you get any Voltage reading at all when you try the test cap., I f you have two 22 you can connect them in parallel, or parallel 33 and 22, it will be close enough.

[swofra]

Re: Asus VW246H will not power on

Firstly, hope your dental surgery went splendidly, or as splendidly as something like that could go.
I plugged in the board to a GFCI without it connected to the logic board (logic board cable still attached to power board but its not to logic board - hope that doesn't matter).
Tested the VDC between the output terminals of the bridge rectifier and got 160VDC to verify my meter and power connection was working.
I tested the VDC between GND JW20 and Point A JW17 by putting one probe on each. I tried reversing the probes as well and also tried doing it on the green side by touching a probe to one of the solder points on JW20 and using the other probe to touch one of the solder points on JW17. All tests showed -0 VDC after about 2-3 seconds. i would imagine that would mean there is zero power between the two.

I take it from your suggestion that not getting any VDC somehow means that C606 could be bad and I should replace it? I will look to see if I have any 22 ~47uF 25VDC caps on old boards I've saved, if not, is your recommendation to order one? Looking at that cap, it says 47 uF 50V, do I need to match that exactly?

Thanks again!

[budm]

Re: Asus VW246H will not power on

Notes: do not touch anything on the board with your hands or body, you to need to at least plug the board under test into the GFCI outlet to protect yourself.
OK, just power up the power supply board by itself without any cable connected to the main logic board, then check DCV Voltage on the top side of the board between 'GND' (jumper JW20) and point 'A' (jumper JW17 to see if you have any DCV there or not.

Do you have any 22 ~ 47uF with 25VDC rating or higher? If you do not get any Voltage reading from the test above, you can try replacing C606 start up cap to see if the power supply will start up.

[budm]

Re: Asus VW246H will not power on

I am sorry I have been very busy with so many people PM me for helps.
Tuesday tomorrow I am having by dental surgery done so more likely I will be on pain med for a next couple days, I hope you can wait.

[budm]

Re: Asus VW246H will not power on

Bud,
Thank you for the reply! The R615 resistance was 0.3 ohms. Attached are pics of the board. Also, just want to make sure that testing the solder points on the green side of the board is effective as testing the top of the board.
Thanks again!

OK, thanks for the pictures, I will download them and mark the test points for you to test tomorrow, it is 1AM my Bay Area time right now and very busy with so many people every nights, so good night for now.

[swofra]

Re: Asus VW246H will not power on

Bud,
Thank you for the reply! The R615 resistance was 0.3 ohms. Attached are pics of the board. Also, just want to make sure that testing the solder points on the green side of the board is effective as testing the top of the board.
Thanks again!