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Hello there, I have a IBM Thinkpad 390E, when i bought it, it came with an AC Adapter and a battery that was completely dead... So i bought a battery and loved it... Well i bought a car adapter for my laptop, and when i was reading all the diffrent voltage settings and such.. i wanted to make 100% sure that i had everything set up properly, so i wouldn't destroy my laptop....
Well i had the 16 V setting right... but when it came to my Polarity setting... there was the setting on the AC Adapter i could go by, or what was right above my power input to the laptop... Only thing was, is there was no indication of how it was sopose to be. - to + or + to -. depending on how you look at it.. Well in both a haste of wanting to test it and having to guess via the laptop .... I plug the thing in with reversed polarity..... !POP! *i unplug it within 1 second* and it begins to lightly smoke.... i almost crapped myself thinking that i just ruined my laptop.. But it turns out, i turned it on via battery power..... everything seemed to work perfect.... i plug it into the wall with my AC adapter, and it worked perfect....

But now my laptop will no longer charge my battery i spent all that money on...
I did a little reading around on the internet and from what i understand... the laptop has fuses and diods to prevent a complete fry of the entire computer in such a case as reversed polarity....

Now that you know the situation. my very serious question is..... Can this be fixed?
Do i have to replace and solder a diod or fuse?

Any information that i can get on this subject would be a great help to me..

Thank you

- Scott Harrington

If you want to reply directly to me, my email address is beavit@hotmail.com

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Last Post by jwenting
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I had the 16 V setting right... but when it came to my Polarity setting... there was the setting on the AC Adapter i could go by, or what was right above my power input to the laptop... Only thing was, is there was no indication of how it was sopose to be. - to + or + to -. depending on how you look at it.. Well in both a haste of wanting to test it and having to guess via the laptop .... I plug the thing in with reversed polarity..... !POP! *i unplug it within 1 second* and it begins to lightly smoke.... i almost crapped myself thinking that i just ruined my laptop.. But it turns out, i turned it on via battery power..... everything seemed to work perfect.... i plug it into the wall with my AC adapter, and it worked perfect....

Most IBM laptops, like most modern laptops, have polarity protection. This consists of a diode across the DC input. Where the power goes in, there's a picofuse, a very small fuse that looks like a liitle green resistor. Downstream from that is the diode. Normally, the diode is reverse-biased, an open circuit. In the event of a polarity reversal, the diode becomes forward-biased, an electrical short. This draws sufficient current to blow the fuse, protecting the rest of the circuit.

What you now have is a blown fuse and, possibly, a shorted diode--thought it's possible that the diode survived, just got hot--hence the smoke. You will need to find the PDF service manual on the IBM site (I can't do all your work for you ;)) for disassembly instructions and replace the picofuse, then check the diode. Even the cheapest (~$10 at a hardware store or Radio Shack) volt-ohm-milliammeter (VOM) will do this just fine. You need to find a full-line electronic supplier in your area, and you will have to buy 5 picofuses to get one (but then you will have spares, right?). If you don't know what I mean by full-line supplier, ask your local TV repaiman where he buys his parts locally, or ask a computer repair shop, or ask either one if he will sell you a picofuse of the correct rating for a price.

Of course this presupposes that you are able and willing to do a little mechanical disassembly and soldering to save a ton of money. :)

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Most laptops have polarity protection, you probaly just blew a fuse, and that can jsut be replaced. But I am nto exactly sure on where the fuse would be located at.

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I got the same problem with my lap tp Packard bell Easy Note E3228.
any help where I can find the PDF service manual or where I can get help to solve this problem .
Any help is great
Thanks for evry body

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I am sure if you check there site they normal have all the pdf files, go to your manfactures website and enter the machines sort code or something. Also did the laptop come with a cd with all programs on maybe the manuals are on there also. If not you may have to phone them :(

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Hello,

Be aware that any hardware hack will void your warrenty, and if the machine goes up in smoke because you did a bad solder job, you are looking at new parts. This is not for the casual person.

If you insist on doing the hardware hack, you might wish to use one of those spare diodes and make a practice run on a different piece of circuit board. When you go to the store to get your diodes, ask the clerk for a little 2 x 2 or 2 x 4 circuit board, and some small solder. Practice soldering before you even unscrew your laptop.

Christian

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If you can recognize the basic components on a pc board, know how to trouble shoot the basic components with a DMM, and have some through hole soldering skills you might want to try fixing this. If you don't, I would recomend that you pay someone with the proper skills to make the repair. If you aren't competent in these areas you could make the problem worse.

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I disassemble the laptop and I can't see any strange things there , now I charge the battery externaly by pluging it directly with the charger and it charge Ok and I can start the computer Normal every thing seams to work Normak , but again if I plug the Charger to the laptop won't charge !!!!!!
Battry --Ok
Charger --ok
the computer work -- ok
But I can't Charge the battry throwe the Normal way !!!!!?????????
Any help there Pls.
Thanks

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If you have a VOM, remove the battery and see if you have any output to the leads.

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Seems the charging circuit's fried, not the polarity protection on the mains inlet.
Either the charging circuit has its own protection (likely) or it's a goner and needs replacing (which in a laptop could mean replacing the mobo depending on the design).

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