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7 Posts

07-15-2020

United States of America

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Backlight and Display Fuse Values for IdeaPad L340-15API

2020-09-09, 19:10 PM

A minor fall took out the display on our 81LW IdeaPad. I am in the process of replacing the display and have found that fuses F4 & F11 are also open on the system board (5B20S41809). It is a HSB motherboard # SBB0T42474. This is an AMD Ryzen 5 3500 that has been upgraded to Win 10 Pro. I have been unable to find any information about the value of these SM fuses. This laptop is still under warranty, but not covered for disasters from falling. The local repair depot is only authorized to make repairs on the board level and of course a new MB is more than half the cost of the whole unit. Bridging the PCB foils with the proper value fuse wire will take care of this problem, but I will need these values to complete this repair. Is there anyone out there willing to share this information with a 45+ year senior technician so I don't have to deep six this relatively new laptop?

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1189 Posts

05-14-2020

United States of America

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Re:Backlight and Display Fuse Values for IdeaPad L340-15API

2020-09-14, 16:07 PM

Hello,

 

Have you raised a question with Lenovo Technical Support / Technical repair departments?  They may be able to provide exact amperage ratings for the fuses.

 

Another way is to find the electrical specifications for the display, especially maximum current draw, then make a judgement on how much more than that the fuse should be.  If you guess too high for the fuse amperage value, then the GPU becomes the fuse......

 

Be gentle with the soldering iron, modern circuit boards are not intended to be soldered by hand, so can easily be damaged.  Complicated circuit boards often have more than one layer of circuitry.  So an over agressive soldering action on the surface could result in hidden short circuits between layers.   If the repair attempt fails, be prepared to purchase a replacement motherboard.

 

Sincerely,

Usedtoberich

 

 

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19 Posts

07-30-2017

United States of America

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Re:Backlight and Display Fuse Values for IdeaPad L340-15API

2021-07-22, 14:23 PM

I have just been on your journey.

 

You were looking for F2 all along. Mine is now a solder bridge ;-)

 

Cheers,

 

noworky

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7 Posts

07-15-2020

United States of America

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Re:Backlight and Display Fuse Values for IdeaPad L340-15API

2021-07-22, 15:50 PM

Yes, an F2 bridge was the final solution. I used a 2A fuse element to bridge the lands. However, after this fix, I did order a MB because my Bluetooth still was not working. A word of caution though, when the alleged new MB arrived it would not operate the SDD. Encompass sent a used board and sold it to me as (full price) new without ever assuring it was working. Seems there is a parts shuffle going on at the factory parts distributor. Through this I found out that they are extremely difficult to work with on returns (as well as being rude), but generally a quick ship. They did not have any other motherboards in stock, so I was just happy to get a refund and move on. Bottom line is that I still don't have working BT, but everything else runs almost perfectly. I'm not going to go on with the chapter in this laptops history when I sent it to the Lenovo depot in Texas for repair though. Suffice it to say they really have no clue what they are doing there and despite telling them not to factory restore the HD they did, even though the BT is purely a hardware problem.

 

Since then I have purchased a HP Pavilion with all the bells and whistles instead of the Lenovo I have been trying to get. Seems Lenovo USA has not stocked much since the lock downs. I moved into a Ryzen 7, 4700U with AMD graphics, an IPS 1080P display, backlit KB, fingerprint reader and a 1TB SSD for about 35% less money. It has a much  sturdier feel as well.

 

I've been using and recommending Lenovo products in systems for my customers for years, but that has changed since this incident. As a long time service technician my mantra has always been that after the sale, it's the service that really counts. Lenovo would be wise to improve on both before their name in the market becomes further tarnished.

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7 Posts

07-15-2020

United States of America

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  • Message 5 of 5

Re:Backlight and Display Fuse Values for IdeaPad L340-15API

2021-07-22, 15:54 PM

Yes, an F2 bridge was the final solution. I used a 2A fuse element to bridge the lands. However, after this fix, I did order a MB because my Bluetooth still was not working. A word of caution though, when the alleged new MB arrived it would not operate the SDD. Encompass sent a used board and sold it to me as (full price) new without ever assuring it was working. Seems there is a parts shuffle going on at the factory parts distributor. Through this I found out that they are extremely difficult to work with on returns (as well as being rude), but generally a quick ship. They did not have any other motherboards in stock, so I was just happy to get a refund and move on. Bottom line is that I still don't have working BT, but everything else runs almost perfectly. I'm not going to go on with the chapter in this laptops history when I sent it to the Lenovo depot in Texas for repair though. Suffice it to say they really have no clue what they are doing there and despite telling them not to factory restore the HD they did, even though the BT is purely a hardware problem.

 

Since then I have purchased a HP Pavilion with all the bells and whistles instead of the Lenovo I have been trying to get. Seems Lenovo USA has not stocked much since the lock downs. I moved into a Ryzen 7, 4700U with AMD graphics, an IPS 1080P display, backlit KB, fingerprint reader and a 1TB SSD for about 35% less money. It has a much  sturdier feel as well.

 

I've been using and recommending Lenovo products in systems for my customers for years, but that has changed since this incident. As a long time service technician my mantra has always been that after the sale, it's the service that really counts. Lenovo would be wise to improve on both before their name in the market becomes further tarnished.

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