No power into the inverter board (no backlight) *PIC*

[The Tim]

I've got an SL500 that one day just decided to stop lighting up the backlight. I tried replacing the inverter board, no change. I tried replacing the screen, no change. I whipped out my multimeter and beeped out the cable running between the main board and the inverter board, and it tested fine. I tested for a DC voltage into the inverter board with the laptop powered on, and got nothing.

Any ideas what could be causing this? I'm going mad here trying to solve this problem. Am I down to the point where I'm going to have to replace the main board for $300-$500?

Has anyone else experienced anything like this before?

[Harryc]

I've never seen the board on an SL500, but generally speaking Thinkpads have several fuses right around the LCD connector area on the systemboard. Check these for continuity with a multimeter.

[The Tim]

Thanks for the suggestion. I'll take it apart again tonight and see if I can find any fuses. I did try a little bit of reflow on some of the components near the connector on the main board that goes to the inverter, just in case some lousy lead-free solder had cracked or something. That didn't make any difference.

[Twisted Mind]

Hello,

I've also never seen your kind of systemboard. But in T4x and X6x it's Fuse F3 on the systemboard.
On both machine it is a 3A, 32V SMD-Fuse marked "P".

http://www.schurter.co.uk/pdf/english/typ_USF_0603.pdf

Regards Klaus

[The Tim]

I've also never seen your kind of systemboard. But in T4x and X6x it's Fuse F3 on the systemboard.
On both machine it is a 3A, 32V SMD-Fuse marked "P".

http://www.schurter.co.uk/pdf/english/typ_USF_0603.pdf

Looks like that's exactly my problem! Just like you said, there's a SMD fuse marked "P" a little below the connector to the inverter board, in the path of the positive DC supply to the connector. I beeped out the fuse and it's open.

Thanks for the datasheet. It isn't a stocked item at Digi-Key, but I was able to find an appropriate cross, LittleFuse part # 0467003.NR

https://docs.google.com/uc?id=0B6MYXGL3 ... OGIw&hl=en

Admin edit: Removed inline image (~190KB) and replaced with link

[Twisted Mind]

If you are not a professional in soldering, I advise you to "Huckepack" assembly of the new fuse.
Simply solder the new fuse on top of the old one.
This avoids thermal deformation during solder out the old fuse and in the new on the system board.
Temporarily, if you have to work, you can just bridge the fuse with some solder. For sure that should not be a permanent solution ...

Regards Klaus

[The Tim]

Photo again: https://docs.google.com/uc?id=0B6MYXGL3 ... OGIw&hl=en

My new fuses came in and I started off by soldering one to the parallel empty fuse footprint just above the blown fuse in the photo linked above. Turned the laptop on and still no backlight! Checked the fuse I had just installed and it was blown too!

Since I had already replaced the inverter board I knew that wasn't causing the fuse to blow, so I started poking around on the main board looking for shorts. Long story short, it turns out the large SMT capacitor just to the right of the fuse in the above photo had failed short, and therefore was creating a dead short between power and ground. After pulling the capacitor off I verified off-board that it had failed completely short.

I pulled the capacitor off and replaced it with one from a scrap board I had lying around from something else, pulled both the dead fuses off and put on a new fuse, and voila--we have backlight again!

Thanks again for your help, Harryc and Twisted Mind!

[Der Goldi]

Hallo,
i think, i have the same problem. I have no backlight and the fuse "P" is also out of order. Have you any idea, what for a capacitor i need. I can´t find tecnical datas from the capacitor.

Thank you for your help.

[Der Goldi]

I have also backlight again. On my mainboard were also the fuse and the capacitor out of order. After changing this, i have backlight again.
I have used the capacitor: 1206.10UF.25V.X5R and the fuse 0603,V FAST ACTING,3A

Thank you Twinted Mind and The Tim for your help.

[totality99]

Thanks for this. I had exactly the same problem. Using this info, I replaced the shorted capacitor, and just bridged the blown fuse with a very thin strand of wire (new surface mount fuses difficult to obtain, expensive, and must be bought in large numbers..). SL500 now working again.! Cheers for your pioneering work The Tim and Twisted Mind.

[inova]

I can not obtain this capacitor in my country. What other can I use instead of this one?

[michelvd]

Maybe an old topic but I was very happy to find it.

After ordering an inverter from China and discovering that that was NOT the faulty component I found this post.

On my wife's SL500 the capacitor also shorted out and the fuse blew. I removed the capacitor and replaced it with a nonSMD one (10uF/25V)

Fuse is replaced with a very thin wire for now, will try to get a fuse but I do not want to order them from digikey (I'm in Europe).

The SL500 is working again (phew, now I can buy a new laptop ).

Thanks again for the posting !!

regards,

Michel

[inova]

I have successfully repaired my SL500. I have replaced the fuse and the capacitor, as mentioned in previous posts. I have managed to find suitable SMD components, although I had to buy 10 fuses and 3 caps minimum (nevertheless, it was all app. 10EUR)

The layout of my motherboard is slightly different from the one on the photos in previous posts, so I will give the photo, for future reference.


I have replaced capacitor, but since my soldering equipment is not so suitable for SMD, I decided not to remove old fuse but to simply put the new one ABOVE the old one. Then I put some solder on the ends and it worked.
Once again, THANK YOU all of you for giving me hint on this problem.

[Oldmoviesfan]

Gents, I cannot express in words how much I apreciate your post on this matter. With this post I be able to fix My Thinkpad SL500 saving a lot of money on screens & motherboard replacement (without mention inverter card wich I already find a replacement from a friend but didnt work as you can imagine). My only expenses was a little amount of soldering stain & patience, because I find the cap from a scratched laptop.

Again, Thanks a lot guys...good work.

[alexgpunkt]

Hello,

i have a littl question.
Unfortunatelly i destroied a little part.
It is the little part next to the fuse on the left side.
I put another part which looks same ^^
But it doesn't work...
I already overbridged this part and the screen was on.... so do you know the specification of this part?
Is this a capacitor too?
Or a resistor?

Thanks, and sorry for my english... i'm out...

[Hendre]

Hi,

Thank you for the information. I want to know what is the capasitor details seeing that the fuse i odered is coming from thu uk and taking a month and a half to get here. I can get that aswell while i'm waiting for the fuse. I don't want to wait a mont and a half for a fuse and then again for the capasitor.

Any body please help.

Thank you!!!

[Twisted Mind]

@Hendre: As mentioned here the datas are:

Cap: 1206.10UF.25V.X5R Typ: TMK316BJ106KL-T
Fuse: FUSE,0603,V FAST ACTING,3A Typ: 0467003.NR

Maybe this helps?



Regards Klaus

[Monkeywrench]

This thread just keeps on giving. Helped me track down my blown fuse quick and easy. Thanks!

[sampath bandara]

i have got same problem. Back light is not working

here forum.thinkpads.com/viewtopic.php?f=46&t=103841