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R31 repair story

R30/R40, A30/A31, G40/G50 and Z60/Z61 Series. NOT for AMD-Ryzen.
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SMA
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R31 repair story

#1 Post by SMA » Fri Apr 18, 2008 5:19 pm

I bought one almost complete r31 and one r31 board. I got them from different sources. Both were obtained as defect.
Of course my only concern was to get the complete machine up and running. Initially it was completely dead - no sign of life at all.

I started out by inspecting the board in the complete r31 and quickly found a missing component.
Trying to find out what the component at that position was supposed to be, I took a look at the other board and found that the same
component was also missing on that board.

It took me some time to figure out what that component could possibly be, but after all, it was not that tough.
The traces are going to ground and to pin 21 (the VL pin) on the max1631 chip - and looking into the datasheet I found that a 4.7 uF capacitor
is expected. Having verified on a couple of other ThinkPad board, that a 4.7 uF is the component normally used, I decided to solder one
into the first board. And it worked.

Just for the fun of it, I soldered a similar capacitor into the other board, and that worked too.
But that board also has another error - it will not display on external monitor - only on the internal LCD. But I do not care about that for now.
I have got a working r31.

By the look of the solder pads where the capacitor had come off, I will say that the root cause here was the component itself.
After getting bad, the capacitor had started to generate heat internally, thereby melting the solder.
And being located on the bottom side of the PCB, sure it would fall off and get lost. It is only 3 mm long.

ajkula66
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#2 Post by ajkula66 » Fri Apr 18, 2008 6:33 pm

A great success story indeed! Congrats and thanks for sharing!
...Knowledge is a deadly friend when no one sets the rules...(King Crimson)

Cheers,

George (your grouchy retired FlexView farmer)

One FlexView to rule them all:A31p

RIP: T43pSF

Abused daily: T520, X200s


PMs requesting personal tech support will be ignored.

Thane_Bitter
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Excellent work!

#3 Post by Thane_Bitter » Sat Apr 19, 2008 11:13 am

That is some excellent detective work SMA, Congratulations! :D
- End of Line -
R31 2656-6FU 1.13GHz, 256MB + 512MB, 80GB 7K2 HDD, Ethernet, Wireless & Modem.

365XD 2625-DEE 100MHz, 24MB, 1.0GB HDD

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#4 Post by tfflivemb2 » Sat Apr 19, 2008 1:40 pm

Congrats!

Any chance you'd be able to post a full scan (pic) of the board, an dindicate which component you added?

SMA
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#5 Post by SMA » Sun Apr 20, 2008 12:52 pm

Here is a picture.

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#6 Post by Harryc » Sun Apr 20, 2008 1:22 pm

I wonder if being in close proximity to the dock port and potential board flex there added to the component coming loose ...

Thane_Bitter
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#7 Post by Thane_Bitter » Sun Apr 20, 2008 8:55 pm

SMA wrote:Here is a picture.
That is some fine soldering SMA! :shock:
- End of Line -
R31 2656-6FU 1.13GHz, 256MB + 512MB, 80GB 7K2 HDD, Ethernet, Wireless & Modem.

365XD 2625-DEE 100MHz, 24MB, 1.0GB HDD

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