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Nec VERSA M500 Laptop - Main power defects on mobo

Hi, this laptop runs well with battery but not with main power supply. The power block is OK but on mobo no led, no fan, no battery charge, nothing... I've 19V behind jack connector but not after the first component beside connector : it looks like grilled resistor, but not sure... referenced PF501 on mobo, maybe a fuse (why "P"...?) but often wide green component (not here...).
0V continuity is OK everywhere on mobo from jack.
What's this component ? and characteristics ? may other ones be damaged ?
Thanks for your help...

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  • mulder1622 Jan 27, 2008

    Hi Danasaur, thanks so much for helping...

    However, it's difficult to believe in this mutant component, overall I didn't find anything on it on the net...(?) Find below the picture, sorry my camera is so bad I can't have better pics, I hope you can see something and find solution.

    thanks and regards.


  • mulder1622 Jan 29, 2008

    I Danasaur,

    Sorry again (not SONY...) for bad picture.

    The component is flat and rectangular without cylinder, really like a resistor, I don't think it's a choke and nearly sure it's a resistor or may be a fuse.

    Unfortunatly, it is grilled because has no resistance and second pin seems to be shorted with ground (near 0 ohm), so I think there is an other damaged component (maybe current regulator or something like that) due to an overload...

    Thanks again...

    I Richard,

    First steps... thanks for trying.



  • mulder1622 Feb 06, 2008


    I've found the solution ! This component "PF.." is a normal fuse, I've red "FU" on it with a spyglass so I was sure something was shorted. I've checked condensators, resistors and diodes near the connector and... a diode was conductive in two directions...

    I've changed the fuse and diode... Waaaouh !!! all is right.

    So why "PF.." ? in fact all other components in this part of the PCB are "PR.." "PC.." "PD.." marked, I think P is for Power... not for Polarized...

    Thanks everybody.


  • Domingos Mar 15, 2008

    I have de same problem as you. It seems to like that you find de solution. I tried everything but i cannot find the diode that you are talking about. Please send me a picture which parts you have changed. I have, i think, another motherboard, but it's like almost the same as yours.
    Please help me. I also cannot changed the parts, but i have friends they can do that for me.

    At the moment a just have desolded de powerjack, but a cannot find anything

  • canidiot70 Feb 03, 2009

    I have the same problem with my versa, who here would like to take on a soldering job at a reasonable price??????
    Thanks, Rod.



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Hi There.

Measure your AC-Connector using multimeter while the ac adapter is connected to the motherboard you should read exactly same as your AC-adapter if you are reading low value your motherboard is shorted if you are reading same value in ground to ground you have connector problem replace the connector. if motherboard short find the faulty parts and replace.



Posted on Jan 28, 2008

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You are going to think this is a fairy tale, just like I did, when I heard of these. It is a "polarized fuse". From the best I can grasp the component, it is a cross between a diode and a fuse. Because you have a device that has potential DC power source originating in two different locations (battery and PSU), a PF is often deployed to protect each circuit separately from overload/shorting. With a PF, the laptop can theoretically survive a overload from either source while both are utilized simultaneously. For instance, the PSU might pop its PF, and if the battery is charged, the laptop can still continue. And it is really critical to replace it with the same polarized fuse, with the same exact rating. That will NOT be easy. They are rare, most semiconductor suppliers do not carry any or carry few variations. The manufacturer usually custom orders these. There is a possible alternative solution. But to be sure, I need to see a photo of the section of MB with this PF and its peripheral related components. I have a Versa, but it is a 2006 model. No PF. Take a clear shot and post it here. Then if I recognize it, I will get back to you.

Posted on Jan 27, 2008

  • Dana Stienheimer
    Dana Stienheimer Jan 27, 2008

    Hmmm. Pretty weak resolution for a SONY. Can't make much out. not even the outline of the PF. Leaving me in the dark, needing more questions: (1) Is this PF component kind of flat and square with a cyllinder form merged into the shape? if so, it might just be a choke. That would be a useful "front line" at the input, to clean up any noise in voltage supply. (2) is that 4 lugs I see on the input jack? If so, are there 4 connectors to the input? If so (again), you have a separate MB power and charger power line. There should be 19 V on both. (3) if you have a standard bayonet (2-wire) like the NEC here, ignore 2 above. (4) is the amp rating on your PSU 3.42, like the NEC PSU here?

  • Dana Stienheimer
    Dana Stienheimer Jan 30, 2008

    OK Mulder. It seems it is a polarized fuse. As I mentioned before, chances of finding one are remote. I suggest desoldering it from the board to identify it, and then, attempt to substitute a diode/fuse in series, to patch the function.

    BUT FIRST, just to be sure this is at fault, try a few simple precautions:

    First, check the resistance and continuity of all the components nearby, again, being sure to REVERSE the VTVM test leads for each reading. This is because your perception of a damaged component may simply be altered by its reverse voltage resistance (as in diodes). Components that employ diodes will typically have zero or high resistance in one direction, but not in the other. Only checking each gap twice, with leads reversed, will identify this.

    Next, if the results are the same, and that component still appears to be defective, try one more thing before you remove it:

    With a very small tipped (and clean) soldering iron, reheat /re-solder all connections to/from the power jack, even its anchoring/ground lugs. This may be all that is wrong with your MB. Very often, I have found that an invisible crack or fatigued connection there, caused by normal stress of use, insert/removal and the occasional wire trip, can cause VERY bizarre symptoms. The low voltage of a VTVM can be passed easily across a cracked connector, where the larger PSU voltage supply cannot. Conversely, the erratic continuity can cause false readings across the peripheral components, and make them appear to be defective when they are not. Best to be safe before you remove the PF and try substitution. I urge you to take this advice seriously. It is easy to dismiss, but 9 out of 10 times, when I am down to a laptop MB, this is all that is wrong, unless a definite short/overload suspicion is justified (like plugging in a bad USB device or shorted peripheral). This is quite worth the 5 minutes it will take.

    I would even take this precautionary suspicion to the PSU itself. The cord, if fatigued or broken internally, or the cable/jack connection to/from board/cable is bad, can give good voltage indications to a VTVM, but fail to deliver sufficient amperage to the laptop. I personally would not de-solder that PF until I had re-soldered all jack connections, and tried a "universal laptop PSU" first. PSUs can have battery-charging voltage sensors that monitor the voltage during load, and cut off, if it drops or exceeds tolerances. This can be true even with a two-wire PSU cable supply, on many laptops.

    After that, if your laptop still does not light up, you will need to go with the initial suspicion. Remove the PF. But after that, and before anything else, I will need a GOOD photo of the device, to suggest which lug points would have diode/fuse connections. Simply cannot do this blind. Also, provide a "truth table" of all resistance readings to/from all possible lug combinations. And that would include both polarities on readings (red lead to lug A, black to lug B / and reverse- Black to lug A and red to lug B, etc)



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