IBM PS/2 L40SX Laptop issues, tantalum capacitor exploded.

[RWallmow]

I recently picked up a L40SX, after having wanted one for quite some time (a friend owns one, and I fell in love with it). Well upon first power up I was greeted with nothing but a smell of hot electronics, so I popped it open, powered it on again to find what was getting warm, and instantly watched capacitor C182 near the rear of the case shoot sparks out of its ass (attached photo).


I had my friend take photos of his board and the layout and component numbering is completely different, so obviously we have different revisions. I also noticed the header that is populated with some jumpers bridging them on mine, is populated with a small PCB with a fuse on it for his. So it looks like someone in the past may have just pulled and bridged the fuse for mine, ugh.

Hopefully another L40sx owner out there has the same revision as mine and can tell me what that capacitor value is so I can try to replace it, if no one can help on that I may just remove it and see what happens without it, or find a similar package cap elsewhere on the board and substitute one of that value. Also hopefully a shorted tantalum cap is ALL that was wrong with this one, but who knows.

 

[Stone]

Is it short or open?

Does the board function as is?

If it seems to function normally the cap is undoubtedly open 'cause if it were short... well you know.

So, if it's short and the board seems dead remove it and see what happens. Many times a board will function without this type of cap and then you can hunt one down to replace it knowing that's (likely) the only damage.

 

[RWallmow]

Is it short or open?

Does the board function as is?

If it seems to function normally the cap is undoubtedly open 'cause if it were short... well you know.

So, if it's short and the board seems dead remove it and see what happens. Many times a board will function without this type of cap and then you can hunt one down to replace it knowing that's (likely) the only damage.

I suspect it was shorted, the cap lit up like the north star so I pulled power, I doubt it would do that if it had failed open. I will probably remove the cap and try to power it and see what happens. Since it appears the board fuse was bridged by a previous owner, I am glad I didn't really let it dwell very long with power applied, I hope the cap is the only casualty and that the traces didn't melt off the board or something. Undoubtedly if the fuse was intact it would have probably popped before that shorted capacitor, I might attempt to rig up my own fuse for future testing.

Also the system was not ENTIRELY dead, there were some signs of life from the status LCDs, but the main LCD never lit (could have a bad backlight for all I know), and it never beeped or showed any other signs of POSTing.

 

[Stone]

I suspect it was shorted, the cap lit up like the north star so I pulled power, I doubt it would do that if it had failed open.

I dunno... I've watched them explode like that and the end result was open. It didn't fail open -- it shorted and destroyed itself immediately so that the result was an open because all the conductive material was either blown out or melted away.

 

[GiGaBiTe]

I can't tell if that's a through-hole radial tantalum, or a SMD tantalum, but you can usually get away with replacing them with electrolytics or ceramic caps if they're not used for something important.

 

[RWallmow]

I dunno... I've watched them explode like that and the end result was open. It didn't fail open -- it shorted and destroyed itself immediately so that the result was an open because all the conductive material was either blown out or melted away.

I removed it today, it WAS still a dead short. The rail its across is NOT otherwise shorted, still no luck with it removed though, the indicator LCDs light up even with power switch in OFF position, and main LCD glows slightly in OFF position, in ON position the main LCD goes dark, and most of the status LCDs go out, just what I believe is caps lock stays on.

It was a SMT, tantalum I believe, its scorched but it LOOKS like it said "205 22K" on it, which matches up to another cap nearby of the same package size. The 205 code would seem to indicate 2.0uf (I don't have any 2.0uf's of any kind in my stock, have a few 2.2's though), but not sure what the 22k indicates as far as temp and voltage.

 

[markgm]

You're close, it's 225 20K.

 

[RWallmow]

I must have forgot to update this thread, I ended up replacing that capacitor (dont remember the value I used, I think it was a 2.2), and ANOTHER tant (under that VRM heatsink) shorted after that, I had to desolder the heatsink and replace that cap too. But ultimately I did get this L40sx working, ran it for several hours and it's running great.

 

[PeterNC]

Nice restoration. Most people, including me, would have binned it already.

 

[my03]

Hi,
and sorry for digging up this older thread. I also have an L40sx with some issues (i actually have two of them, but the first one works just fine for the moment). The second one (the trouble-maker) does differ on the system-board compared to the working one as it more mimics the OTs L40sx above. When i got it, it had some issue with the screen (only half the screen would display properly unless i pushed the thumb ever so lightly on the right-hand side of the bezel in which case the full screen would show. Recently, i noticed that it stopped working properly (as soon as you put the psu-connector in, it starts up but will not shut down when powering-off by using the regular button for this. Also, the HDD can no longer be detected (i have replaced the Conner with a CF/ide card that i use in various other machines). But the big issue is that it emitts a "fishy smell" from the top-right side of the laptop (where these 2+2 larger capacitors sits).

I have ordered and recieved replacement capacitors (Panasonic branded ones) and i also intend to recap the inverter-board inside the screen bezel (i did that on the other laptop and it turned out extremely well going from weird screen to fully normal). But i'm not sure since as i need to push my finger ever so slightly on the bezel for half of the screen to show, if it is the capacitors or the flex-cable itself that causes the issues?

Have anyone encountered a laptop that will not shut down + this same screen issue?

 

[super-sama]

Hi,
and sorry for digging up this older thread. I also have an L40sx with some issues (i actually have two of them, but the first one works just fine for the moment). The second one (the trouble-maker) does differ on the system-board compared to the working one as it more mimics the OTs L40sx above. When i got it, it had some issue with the screen (only half the screen would display properly unless i pushed the thumb ever so lightly on the right-hand side of the bezel in which case the full screen would show. Recently, i noticed that it stopped working properly (as soon as you put the psu-connector in, it starts up but will not shut down when powering-off by using the regular button for this. Also, the HDD can no longer be detected (i have replaced the Conner with a CF/ide card that i use in various other machines). But the big issue is that it emitts a "fishy smell" from the top-right side of the laptop (where these 2+2 larger capacitors sits).

I have ordered and recieved replacement capacitors (Panasonic branded ones) and i also intend to recap the inverter-board inside the screen bezel (i did that on the other laptop and it turned out extremely well going from weird screen to fully normal). But i'm not sure since as i need to push my finger ever so slightly on the bezel for half of the screen to show, if it is the capacitors or the flex-cable itself that causes the issues?

Have anyone encountered a laptop that will not shut down + this same screen issue?

sounds like a flex cable problem. Get the capacitors replaced and verify the machine otherwise is stable aside from the display and work on that afterwards. It might be that you'll need to add something inside the bezel to apply pressure if the problem can't be solved by normal means.

 

[my03]

sounds like a flex cable problem. Get the capacitors replaced and verify the machine otherwise is stable aside from the display and work on that afterwards. It might be that you'll need to add something inside the bezel to apply pressure if the problem can't be solved by normal means.

I will do that. Hopefully its nothing to severe, but if it comes to it, i assume its nothing a piece of cardboard (or similar) can't deal with I'll photo-document it all and link it here for any future reference sake (need to photo the stuff anyway to ensure that it comes back together as it should).

 

[my03]

One leaker ..

Wish me luck

First the system board, then the screen-assembly.

 

[my03]

So i did all the radial capacitors (in green), and inserted a working/new cmos-battery to the unit but the problems remains exactly the same (will not shut off, can't detect the HDD) but it does no longer smell of fish (probably due to the new capacitor that leaked previously).

I guess its now down to these tantalum capacitors that the OP described. Would those be the ones encircled in red?

 

[super-sama]

So i did all the radial capacitors (in green), and inserted a working/new cmos-battery to the unit but the problems remains exactly the same (will not shut off, can't detect the HDD) but it does no longer smell of fish (probably due to the new capacitor that leaked previously).

I guess its now down to these tantalum capacitors that the OP described. Would those be the ones encircled in red?


View attachment 1267692

I'm betting you have a broken trace somewhere eaten away by capacitor goop. I'm seeing a lot of green stuff around Q9 in the middle of the board for instance... Did you also give the board a good vinegar bath and a scrub down with a toothbrush after?


The tantalum caps aren't likely to be your issue but I'd still replace them on principle just to be safe. You can either go with tantalums of the same value or more expensive SMD ceramic capacitors, but the thing you need to worry about right now is identifying why it's not shutting down and what on the drive side is not connected that you're not able to see the drive. Looks to me like you're in for a number of hours beeping out traces until you find the culprit.

 

[freesofia]

Attach my BOM Export Capacitors pack

 

[my03]

Thanks super-sama, you are most probably right and i will do my best effort in cleaning everything up as good as i can. I will do this first and try to catch (using a magnifyer) any broken traces, but if that will not work then i will try to replace those tantalums as well (hopefully it will not come to that, seeing how difficult it would be to try to get that heat-sink off).

I'll report back