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Thread: Sproggy PS HELP

  1. 01-26-2002, 06:32 PM #1
    LoSx
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    Post Sproggy PS HELP

    Ok I made the 2.6 supply and I can get the 5V and the 3.3V and Power good to come out ok

    The +12 -12 and -5 WONT!

    I dont understand why exactly that is. I am thinking it is the LM2587-12T On pin #5 and pin #4 I have 12 V from the car going to it (Or well an atx power supply so i can test it)

    Pin #1 which is the compensation pin is putting out 2.0 volts or so.. pin #3 is ground but the prob is pin #2... what should that be putting out?? Mine isnt putting anything out or if it does its a few millivolts no where near even 1 volt

    Could it be that I destroyed the LM2587 chip or could it be the t6 transformer whichj is a renco rl-5533 ( I dotn think it is the tranformer because it needs the 12V supply from the board on one of the pins... I think it was pin #5

    Could it be that its a bad transformer?? I also tied the 12V from the atx spply powering the thing to the feedback rail and took the feedback rail off so it would appear to pass 12V down.. and then I do get the +12V to work but the -12 and -5 still dont...

    Any help would be appreciated!
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  2. 01-27-2002, 11:08 AM #2
    Miel Gibson
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    OK let's see.
    LM2587:
    Pin 5 is Vin, it should go to +12V
    Pin 4 is an output, it does the switching (pulsing)and it should go to pin 2 of the transformer's primary, the other pin of the transformer should go to +12V, just like pin 5 does.
    Pin 2 is a feedback input, it monitors the 12+ output from the transformer/diode/capacitor chain, you should be getting @ +12 volts from it.

    I suggest you double check your wiring and component polarity around the regulator.

    Good luck!

    [ 01-27-2002: Message edited by: Miel Gibson ]
    If it ain't broken, open it to see what makes it "tick".
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  3. 01-27-2002, 12:52 PM #3
    LoSx
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    You dont think I could have burnt anything??

    I have all the pins correct... I have +12 on the pin #2 of the tranformer and on the switching pin #4 and I have 12V on pin 5 I just dont get a feedback for some reason... I ordered another lm part to replace it and hope that was the problem....
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  4. 01-27-2002, 01:16 PM #4
    LoSx
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    Oh and one more thing is the LM chip from national semicondctors suppose to get SOOO hot??? I mean I know it is suppose to get warm but this thing gets HOT as anything... You cant even really touch it (I have a heatsink on it now) but I didnt at the begining so could that have damaged the chip??
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  5. 01-27-2002, 01:59 PM #5
    Miel Gibson
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    You should be getting a pulse on pin 4 of the LM2587, not steady DC. Check if the SA28A and the MUR120 are not shorted. If they're ok, then try another chip and ALWAYS use a heat sink.
    If it ain't broken, open it to see what makes it "tick".
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  6. 01-29-2002, 08:19 PM #6
    LoSx
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    Looks like the chip was bad but now I am thinking that something else got burned too.. I tried 2 different chips and each gave me close to 3.6 Volts.... I am wondering if the transformer is gone or some other piece..?? Any sugestions??
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  7. 01-29-2002, 08:25 PM #7
    LoSx
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    [ 01-30-2002: Message edited by: LoSx ]
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  8. 04-04-2002, 01:03 PM #8
    mkkbb
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    I too am having these problems - also the LED doesn't come on. I have no wires connected to the output voltages at the moment though. Is this normal.

    Also, how do I connect a heatsink. I have no idea about heatsinks or how they work.

    I would appreciate ANY help.

    Thanks.
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  9. 04-13-2002, 04:08 PM #9
    Mav
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    Also, how do I connect a heatsink. I have no idea about heatsinks or how they work.
    Heatsinks are just big blocks of copper with as much surface area as possible, they just go straight on the part, and work by (i think) absorbing outside cooller air and also radiating the heat, so it will cool it down.

    Have a look on your cpu, in your comp, there should be a heatsink under the fan.

    Hope it helped,

    Mav
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