Asus VW246H will not power on

[tom7688]

Re: Asus VW246H will not power on

Hoping someone from the original thread can reply about how they fix it. Here we are years later, I have the same monitor and the same problem! Hoping someone was successful in repairing and can share what they did.

[Edj628]

Re: Asus VW246H will not power on

Hey gentleman, another newbie here. I have an Asus vw246h as well, and I've discovered that my ccfl tubes were broken up top. I decided to buy a set of LED strips with an inverter board from ebay, and I honestly have no idea how to install it. I do know how to solder. I was wondering if you guys could be of assistance?

Here's in for for the led's and board I purchased. I tried following the instructions on the website, but I'm not very good at deciphering broken English .

www.creatall.com

[Davi.p]

Re: Asus VW246H will not power on

"Are these the diodes Davi.p mentions?" Yes. I don't see cold joints.

[UKRobster]

Re: Asus VW246H will not power on

I have inspected the underside of the board, and have found the attached images.
I have only the research I did on Google to try to identify a 'cold solder joint'.
The first picture shows the component attached, which looks like two items attached either end of a heatsink.
Are these the diodes Davi.p mentions?

Then I have tried to get the best pictures I can of the underside.
I know they are not the clearest images, but do they look like cold solder joints?

[Davi.p]

Re: Asus VW246H will not power on

I would point attention first on the primary side solder joints then the rest, if you don't find anything cracked you could try to heat a bit the thermal resistor with solder iron then power on and see.. it is near the 220vac input connector, if nothing changes change low voltage caps. If you have desire you can first try to power up the monitor with heating and test which voltage you have on the middle pin of the 2 double diodes, since you have 1 only primary output voltage, if is a 12v then you can desolder jumper JW17 and connect an external 12v for test and see what happens.. or at least try to give power to monitor without heating and see if the main voltage on that diodes is present.

[UKRobster]

Re: Asus VW246H will not power on

I have had a look at some cold solder joints. Will inspect the board with a magnifying glass.
The 470uF caps may be too wide. Will check that too.

Thanks for the other advise I think I will try to narrow down which section of the board the issue appears to be in!

[selldoor]

Re: Asus VW246H will not power on

I would say a cold joint on small caps is not common (apart from the ones I solder )
They are usually on larger components that get hot and usually high voltage .On some sets we recommend re flowing the main transformer , inverter transformers , high voltage blue caps, inductors (coils) as a matter of course.
Look on google for pictures of cold joints so you know what to look for and perhaps try to
narrow the search down to a board then funnel the heat with a card tube to try and pin it down to a section. Takes some time but perhaps easier than resoldering and replacing caps at random. Those caps are ok PROVIDING they are not too wide to fit.
I havent looked but panasonic FR or FM would also be good if they are a little cheaper.

Once again if you can try heating just some of the caps to see which ones make a difference to it coming on or not.

Another possibility is using freeze spray to cool certain areas while the set is on and see if it goes off ( more use for bad joints)

[UKRobster]

Re: Asus VW246H will not power on

The other caps on the board are : 470uF 35v & 220uF 25v
I have found these, could anyone confirm they are correct?

470uF
220uF

They are the same make and series as the one I ordered for the start up cap.

[UKRobster]

Re: Asus VW246H will not power on

I used a hairdryer to warm up the other caps. This made the whole board warm, however it did power on.

I will try replacing the other caps and see if that resolves.
selldoor when you mention a cold joint. Could that be on on of the caps? Or do you mean it could be another component? Is a cold joint on the caps common?
What I'm getting at is that I hope replacing the caps will solve this issue.

[selldoor]

Re: Asus VW246H will not power on

I did not actually mean pre heat the start up cap as I knew what you had bought and if you have put it in correctly (asus sometimes silkscreen often is the opposite way to what you expect) it would be fine.

I meant for you to pre heat the other caps as if the startup cap was bad then others may be bad also. It could also reveal a cold joint.

[Davi.p]

Re: Asus VW246H will not power on

i see now the photo, the pin is n.8 and the resistor is r605

[Davi.p]

Re: Asus VW246H will not power on

It's a thin track to follow but i would check if it arrives voltage at the right pin of the pwm ic, start from the + leg of bigger cap and follow the path, it arrives on 1 or 2 resistors with high value that comes in the chip, that is the leg where you must find an high voltage , maybe around 300v i don't know sorry.. have you ever tested psu output/s in this off state?

[UKRobster]

Re: Asus VW246H will not power on

I tried the hairdrier test, but as Davi.p thought, it didn't work.
I thought I would just go ahead and replace the start up cap again.
This hasn't worked either.
It will still not power on

Is there anything else is to try now? Davi.p have you any procedures to offer?

[Davi.p]

Re: Asus VW246H will not power on

"Cap used to replace was recommended by 'selldoor' and is the same rating as the one taken out." Is it a low esr type?
"I will be trying a hairdryer later to warm up the 'startup cap' to see if this will power it on, rather than having to replace the cap." One new cap cannot dry up in less than a month,
if you have used a non low esr the hot air test is a waste of time.
"If I have to do this everytime I turn wall outlet off, then so be it.."
Which life is in that way? Monitors are designed to stay always plugged and last years,
you must repair it and stop.

[UKRobster]

Re: Asus VW246H will not power on

This don't surprise me much since in the previous reasonings there was a thing that doesn't turn me back, if a leaky cap works better if in higher temp. why pulling the wall plug and leave so for hours makes turn the monitor back to work? If the "startup" cap (why "startup"?) was faulty the monitor doesn't turned on only after unplug, since the psu is always on while plugged and little cap is at a certain temp.
We can explain this because with the monitor plugged but OFF the psu circuit goes into a green mode where the frequency is lower and a low capacity cap makes more fatigue when insead at the pluggin in in the wall the chip is fully on and etc etc...?
Then the new cap is low esr and same capacity/voltage as the old one?
"It doesnt always get left on standby, but power cable is in extension lead which is always on"
What do you mean? Is the mon. been unplugged ever this period?

Sorry if my post is a little confusing.
Since early December and initially solving issues, monitor has always been plugged in with power cable, and wall outlet switch has always been 'on'.

Monitor itself is sometimes left on standby (ie: turn off PC but do not touch monitor power button - usually by my girlfriend). But more often monitor is turned off with its power button.


Previous to changing 'startup cap' in December, if I turned off wall outlet power. When turning it back on, monitor would not power on. If I left all cables unplugged overnight, then next day it would power on again. (this is what confuses me, why leave overnight, then work again next day? Doesn't make sense)
That was until December, when it would no longer power on at all.

I changed 'startup cap' and all seemed OK.
Cap used to replace was recommended by 'selldoor' and is the same rating as the one taken out.

I now understand that if monitor is left plugged in and wall outlet 'on' that there is a small current passed through PSU. Therefore monitor functions day after day.

I will be trying a hairdryer later to warm up the 'startup cap' to see if this will power it on, rather than having to replace the cap.
If I have to do this everytime I turn wall outlet off, then so be it..

[Davi.p]

Re: Asus VW246H will not power on

This don't surprise me much since in the previous reasonings there was a thing that doesn't turn me back, if a leaky cap works better if in higher temp. why pulling the wall plug and leave so for hours makes turn the monitor back to work? If the "startup" cap (why "startup"?) was faulty the monitor doesn't turned on only after unplug, since the psu is always on while plugged and little cap is at a certain temp.
We can explain this because with the monitor plugged but OFF the psu circuit goes into a green mode where the frequency is lower and a low capacity cap makes more fatigue when insead at the pluggin in in the wall the chip is fully on and etc etc...?
Then the new cap is low esr and same capacity/voltage as the old one?
"It doesnt always get left on standby, but power cable is in extension lead which is always on"
What do you mean? Is the mon. been unplugged ever this period?

[UKRobster]

Re: Asus VW246H will not power on

Selldoor: Thanks for replying.
It doesnt always get left on standby, but power cable is in extension lead which is always on, perhaps that provides enough to keep cap operational or solder joint warm.
Will try the hairdryer trick, but it will be tomorrow. Will post back with results, thanks again!

[selldoor]

Re: Asus VW246H will not power on

I have not read back all the thread -perhaps other caps need replacing as well.
Or may be a cold solder joint

Has it been left on standby all the time - that might be enough to just keep a cap operational/joint closed.

Take the back off and pre heat it with a hairdryer again then switch on.

[UKRobster]

Re: Asus VW246H will not power on

Hi guys, havent logged in for a while an can see this thread has been busy!
Glad my issues have helped out others.

Im gutted to report that my issues have returned.
Since I fixed my monitor at the begining of December it has been functioing fine.
This weekend I needed to turn off my fuseboard to change an electrical socket.
So I powered off the monitor and unplugged the power cable (although it is plugged into a 6 way extension and this was still switched on at the wall).
When i turned the fuseboard on again, plugged the monitor in, and it wouldnt power on. I unplugged it again and left it for about 28 hours. Tried it again and it will still not power on.
I really dont understand why this keeps happening.
I havent taken it to pieces yet, but will do this tomorrow and try changing the start up cap again (have still got 4 left from before).
But has anyone any idea why this happens? I dont need to be having this issue everytime I have to turn the fuseboard off!!

[blackbulb]

Re: Asus VW246H will not power on

didn't think it would be that simple, thanks for the fast reply!