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Thread: Data IO 29b and magic smoke...

  1. #1

    Default Data IO 29b and magic smoke...

    Double post...please ignore this one.


    ________


    Hi guys,
    Just wondering if there are any Data IO 29b Aficionados in the house?

    Today I was moving my 29b to another area of the house. I'm in NZ which is 240vac, but up until now I was running the 29b off a step-down transformer at 100vac. I decided to change the voltage to 240vac which I did by setting the dial thingy on the back of the unit. Pretty sure this is the first time it's ever been set for a voltage other than 100v.
    I turned it on for about 30 seconds, and all seemed fine. I turned it off at the back of the unit, and went about routing the cables under the table. About 2 or 3 minutes later. I heard a sizzling and crackling noise and I emerged from under the desk to find smoke (a lot of smoke) billowing out of the 29b. I quickly unplugged it at the wall, picked up the unit and rushed it outside (so that I didn't have to suffer the wrath of the wife...too late, the house stank!!!! That horrid sickly burnt capacitor smell).

    I expected to easily find a destroyed capacitor considering how much smoke and noise was produced, but upon opening the unit I have't yet been able to find a single component that looks burnt or damaged!!!!

    I guess my questions are.
    1) Why would it do this when the unit was turned off?
    2) Is it possible that it's not a capacitor thats burnt out (although the smell is very capacitor like). Could it be the internal transformer?
    3) I'm almost tempted to turn it back on so I can find the smoking part, but I'm sure you guys will say thats a bad idea...any other thoughts?

    Thanks for listening and any advice would be most welcome.

    Phil
    retro computing at: www.neoncluster.com ....is dead

  2. #2
    Join Date
    May 2006
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    Melbourne, Australia
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    Default

    Quote Originally Posted by Nama View Post
    1) Why would it do this when the unit was turned off?
    People with IBM PC family computers have reported same. Below is pictured part of the circuit diagram of the power supply within an IBM PC. Note that there are components (C1, R1, L1 and C2) before the switch (S1). Those components are powered whenever the power supply is plugged into mains (house) power.



    The power supply in the Data IO 29b may be similar.

    Quote Originally Posted by Nama View Post
    2) Is it possible that it's not a capacitor thats burnt out (although the smell is very capacitor like). Could it be the internal transformer?
    Given that the failure occurred when the unit was powered off at the rear switch, it does sound like the failure was of a component before the switch, which should narrow down the suspect list considerably.
    Such components will include one or more line suppression capacitors, and their failure is relatively common. Unlike the one pictured at [here], the crack can sometimes be small and/or well hidden.

  3. #3

    Default

    Hi modem7,
    Yes you are correct. I found the burnt out part. It's the Schaffner FN 370-4 filtered power entry module:

    http://www.mouser.com/ds/2/355/DS_FN...ilter-6234.pdf

    That's why it could still smoke when the power was turned off to the unit.

    Does anyone know where I can get one, where shipping to NZ is $50!!!!

    Thanks
    retro computing at: www.neoncluster.com ....is dead

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