Help with dim laptop screen

[NYJimbo]

Yes, it does..

Ok, if it DOES NOT get a tone when you are doing the test (screw to chassis) I mentioned before then there is likely to be a continuity problems.

 

[naulgo]

Ok, if it DOES NOT get a tone when you are doing the test (screw to chassis) I mentioned before then there is likely to be a continuity problems.

It gets a tone when testing the screw to chassis as well. i Apologize for not mentioning this earlier.

 

[NYJimbo]

It gets a tone when testing the screw to chassis as well. i Apologize for not mentioning this earlier.

Did you check for any fuses around the LCD connector to the motherboard ? LED based 1545's should have fuses around the connector. marked with F1 or similar. You can do a cont test end to end on the fuse to see if its still intact.

 

[naulgo]

Did you check for any fuses around the LCD connector to the motherboard ? LED based 1545's should have fuses around the connector. marked with F1 or similar. You can do a cont test end to end on the fuse to see if its still intact.

Found these 2 fuses and test them for continuity, F4 No Continuity, F5 has Continuity. Please check pic.

 

[NYJimbo]

F4 looks like a 2amp littlefuse. Are you sure there are no other fuses around the LCD cable connector on the mobo ? If you are comfortable doing it you could bridge F4 to see if it works. Any fuse showing that its open like that is bad. Sometimes in rare cases the solder from the fuse to the mobo will break from heating and cooling and sometimes just reflowing both sides of the fuse will get it to work.

But if you can bridge it with solder or a tiny wire it should help you determine if that's the fault.

I would not just bridge it with solder permanently as it will not protect the motherboard in the future as it wont blow when it gets hot.

 

[14049752]

This is a Sony we're talking about. Look for F15 or F16. It's usually those fuses.

 

[naulgo]

F4 looks like a 2amp littlefuse. Are you sure there are no other fuses around the LCD cable connector on the mobo ? If you are comfortable doing it you could bridge F4 to see if it works. Any fuse showing that its open like that is bad. Sometimes in rare cases the solder from the fuse to the mobo will break from heating and cooling and sometimes just reflowing both sides of the fuse will get it to work.

But if you can bridge it with solder or a tiny wire it should help you determine if that's the fault.

I would not just bridge it with solder permanently as it will not protect the motherboard in the future as it wont blow when it gets hot.

Success. I bridged fuse F4 as you suggested and image is back on (thank you). What will be the proper steps now, reflow first and see if it fixes the issue or replacing the fuse ? I haven't replaced a fuse before and i don't think i have the right equipment either to do it.
Please check pic below.

 

[naulgo]

This is a Sony we're talking about. Look for F15 or F16. It's usually those fuses.

I've bridged F4 and i got the back light back on. Posted a picture as well.

 

[NYJimbo]

If you are not sure if you can do anything more then you might leave it as is if you think this bridge will hold. Many people will just bridge it and leave it. But the best thing to do will be to buy the correct fuse and put a new one in.

I know this is pretty tricky and you risk doing more damage the more you tinker with a solder joint so you are going to have to decide what to do next. Also be sure to cleanup any little solder or wire bits that might be floating around, they can end up elsewhere and cause more trouble.

Glad to hear this found/fixed the problem.

If I helped you can always click the little "reputation scale" in the upper right of any message. Thank you !

 

[naulgo]

If you are not sure if you can do anything more then you might leave it as is if you think this bridge will hold. Many people will just bridge it and leave it. But the best thing to do will be to buy the correct fuse and put a new one in.

I know this is pretty tricky and you risk doing more damage the more you tinker with a solder joint so you are going to have to decide what to do next. Also be sure to cleanup any little solder or wire bits that might be floating around, they can end up elsewhere and cause more trouble.

Glad to hear this found/fixed the problem.

If I helped you can always click the little "reputation scale" in the upper right of any message. Thank you !

Thank you for your help and of course this will add up to you reputation
I will clean the mobo around it and it seems to be solid and i will leave it as is and test it for 24hrs.

 

[zaoka]

Hi

You should never leave jumped fuse in the circuit!

If that screen shorts again guess what? It will blow motherboard as well.

You can get that fuse HERE

About grounds:
All grounds are the same, you always test ground by using MINUS pole of the DC jack as a reference. Most people is using ground shield of USB jack as a reference which is also good, as long as DJ jack connection is not loose. That ground that got disconnected is used to discharge static electricity that may happen when user touch laptop so instead of causing problems or restarts that charge gets under control.

You could also use multimeter and see if positive voltage is coming to the screen (those 2 red wires). That way you could find out right away that screen is not getting voltage

 

[NYJimbo]

About grounds:
All grounds are the same, you always test ground by using MINUS pole of the DC jack as a reference. Most people is using ground shield of USB jack as a reference which is also good, as long as DJ jack connection is not loose. That ground that got disconnected is used to discharge static electricity that may happen when user touch laptop so instead of causing problems or restarts that charge gets under control.

You could also use multimeter and see if positive voltage is coming to the screen (those 2 red wires). That way you could find out right away that screen is not getting voltage

You cannot always get to the dc jack without tearing the machine apart, also you know that those two red wires are NOT voltage to the LED lines, right ? He had data, just not light. So testing those two lines would not help him in this case.

 

[zaoka]

hi

Hi Jimbo,

I dont agree with you.

He had data, however, was missing DC voltage used to supply LED circuit. These 2 red wires are used to supply DC voltage to the LED circuit and voltage was absent due to open fuse.

Both wires are connected together so that connections on the connector are not overloaded with high currents, this way its separated to two connections.

You can use DC jack ground by pooling DC plug out just a bit so you can touch ground with test probe. This should be reference ground in hard to fix cases otherwise grounding shields of USB can be used instead.

 

[NYJimbo]

Hi Jimbo,

I dont agree with you.

First off those are THREE red wires, not two. Those are 3.3v lines. for lcd logic and driver.

 

[zaoka]

hi

So if thats correct what wires are used to supply LED inverter circuit?

As far as I remember these are the only wires used to supply LED inverter... inside is usually step-up DC converter and distribution chip that does both.

Its not like old CCFL inverters where 19V goes directly to the inverter.. and usually with separate cable.

 

[NYJimbo]

So if thats correct what wires are used to supply LED inverter circuit?

As far as I remember these are the only wires used to supply LED inverter... inside is usually step-up DC converter and distribution chip that does both.

Its not like old CCFL inverters where 19V goes directly to the inverter.. and usually with separate cable.

LED voltage lines are separate.

 

[zaoka]

hi

Where they are? This is the only connector that goes to the LCD LED screen

Find that LVDS cable pinout and you will see.

 

[NYJimbo]

Where they are? This is the only connector that goes to the LCD LED screen

Find that LVDS cable pinout and you will see.

Ok, You go on thinking that there is only one source for voltage on the 40 pin LED LVDS cable and have a good time with your repairs. I am not going to teach you what you could learn yourself.

 

[zaoka]

hi

No offense sir.
Use common sense, why would engineer use 3 wires to supply a voltage for the LED screen and use thiner wires to supply inverter circuit?

Inverter circuit is using most of the power and it needs thick wire and/or more wires..

We booth learn something new almost every day, today is your day

 

[NYJimbo]

We booth learn something new almost every day, today is your day

I'm not going to spoon feed this to you. Here's a picture. Figure it out yourself.