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Thread: NAS Power Suply Fuse

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    Question NAS Power Suply Fuse

    Hi,

    I recently bought a NAS box off ebay. The unit came and it power up fine for 10 second and then suddenly no power.

    I open the unit up and saw the seller added two masive 200v680uF capacitors to the PSU circuit. The cable tie that was holding these down seem to have been broken off during postage. One of the cables from the capacitor to the board got broken off as the result of this.

    I asked the seller as to why these two capacitors are attached like this. The seller told me the unit was undergoe a conversion from 120V to 240V. I am not sure how safe this was but the seller ensure me he has been doing these conversion for years and all his customers were happy. Seeing he has 100% rating on ebay I ignored this and told him to send me a new PSU which is on the way in the post right now from asia.

    Being a curious person, I took out my multimeter and start to do some continuity testing. Not being very electronically minded, everything looks fine except maybe for a little component near the power input of the PSU with NSF T 2.5A 250V written on it. I have a few question from here on:
    1. Is this the fuse for the PSU?
    2. If I do a continuity test, should this give me a beep with my multimetre?
    3. Will a lose Capacitor cable blow the fuse like this one?
    4. Where can I buy this fuse if it is faulty? I can't seem to find this online at Jaycar.



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    Sounds like a fuse to me. Measure the fuse with meter on Ohms. Should read o ohms or if using beep function give a nice beep.
    Any electronic parts store have these fuses. Dont like the idea of a conversion from 120 to 240V. 200v capacitor rating for 120V input may be Ok but if they are across 250V could be hazardous!

    Mind you if he has done this before it may be you only have to resolder the capacitor to where it was attached to and replace the fuse. Might have been the initial surge into the discharged capacitors that took the fuse out.

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    are the caps in series or parallel?
    When I explained to the guy what avatar I wanted, that wasn't what I meant!

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    Yeh, prob a fuse.The T part of the fuse would indicate a slow blow. If it is a pigtail then Jaycar won't have them.
    Likely the caps are in series to give 340uf , 400 V, to drop the voltage down. If so they will be in series and inline with the 240V.
    I've done this with small loads like LEDS and globes before but it seems a bit shonky on a bigger device.
    If the NAS is just 12v/5v maybe a new switchmode is the go.
    I'd rather have a bottle in front of me than a frontal lobotomy...

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    They are wired in series.

    I took it to the engineers at my work and they reckon it is a switchmode power supply so this should work ok.

    I went to jaycar during lunch and bought myself a verticle standing fuse holder that will take the standard globe fuses. They do not have 250V 2.5A fuses so I bought a 2A 250v and a 3A 250V slow blows. I wired them up and they seem to blow instantaneously every time I plug the PSU into the mains.

    Any ideas?



    Last edited by quacka; 28-10-09 at 08:13 PM.

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    Bit hard to tell from the photos what goes where.
    But the fuse blowing straight away means there is a dead short, so possibly
    1. The caps are punched thru and now the PS is blown, the chopper transistor is short etc.
    2. The caps are OK but the PS is stuffed.
    3. The wiring is wrong

    From the look of the output colours it is 12V/GND/5V, so if it were me I'd just replace the PS with a 240V rated one and toss the old.
    I'd rather have a bottle in front of me than a frontal lobotomy...

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    Quote Originally Posted by quacka View Post
    They are wired in series.
    Autotuner beat me to it, ditto his adv.

    just a trick so you dont go through to many fuses, clip on a 100watt globe in place of the fuse, if it goes real bright at turn on, then you havent found the fault yet

    saves popping fuses...
    When I explained to the guy what avatar I wanted, that wasn't what I meant!

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    oh yeah, forgot to add, be REAL carefull playing around.
    The heatsinks are likely live with high voltages, and the caps likely holding over 400V..
    I'd rather have a bottle in front of me than a frontal lobotomy...

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    Thanks for the tips

    I think I will wait for the spare psu to come before I start hacking around the plug and hardwiring it to a new PSU. I have a few spare PSU around but the plug are ATX type and doesn't fit this board.

    Cheers

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