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Thread: Sproggy PS is not a good choice..

  1. #1
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    Sproggy PS is not a good choice..

    Well, the actual supply is fairly good, but the -12volt line REALLY needs some sort of regulation... :P Upon testing it with a single CDrom as the load (drawing 1.2amps max off the 12volts) the -12volts peaked at OVER -22VOLTS!!!! this can't be good.. :P I think that a simple low dropout -12volt regulator should be added to the -12volt line.... they have a max input of -12.6 and a mix of -26, which should keep it happy even with no load on the 12volts... Perhaps Mastero should include this modification it all the PSs he sells?? Or perhaps a modification should be made to teh board to include this.. also, I thoght I should point out, that even with no load on teh 12volts, my -12volts measured over -13volts..
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  2. #2
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    Well that is a very good observation MP3Kid..... good to see people are really experimenting with this stuff....

    But I think the opening statement of the post is a little extream. You may very well be right and we all should investigate the mod you speak of, any improvement is a good improvement.

    But with the numbers out there succesfully using the Sproggy design it obviously is a GOOD design and all in all is probably the best available right now for people doing this.

    But as I stated above, very interesting observation... I will trinker with the idea. I just got the final parts to build two more Sproggy 2.7 PSU's so I will try to duplicate your finding.

  3. #3
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    Yeah, the topic title was abit harsh, but I thought it would get peoples attention... Sure, lots of people are using them, but would you really want to feed your expensive mobo with -8volts more than what it is meant to have??
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  4. #4
    Raw Wave Rob Withey's Avatar
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    Yep, this issue was already identified in this thread:

    sproggy - Testing voltage outputs


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  5. #5
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    MP3KID you posted in that other thread so you must have already known of this problem!!!
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  6. #6
    Maximum Bitrate MikeHunt79's Avatar
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    i`m sure a 7812 linear reg would work, as -12v pulls very little, if any current. I think someone should do a redesign on the sproggy, with this mod, atx startup shutdown (see previous thread) and an optional 10amps on the +5v rail (like the 2.7), and maybe 4 amps on the +12v rail? Call it a sproggy 3.0 or something.

  7. #7
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    Hehe perhaps that'll be my summer project? I guess it should be easy enough - i think the design is sound, just needs to be more powerful. perhaps a double board with a kinda 2.7 but split in half. But well done mp3kid for bringing this to my attention, i must have missed the previous thread. I'd rather feed my motherboard with -12 rather than -22
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  8. #8
    FLAC Mastero's Avatar
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    OK lets get this straight is there even one Mobo which had a problem with the negative 12 volts ??

    Like a properly built sproggy??

    Cause if there was no problem to all the sproggy users i dont think there is much concern for this....

    Cause if this was a major flaw then the sproggy's PSU wouldnt have helped so many

    Mastero

  9. #9
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    I doubt it is a major problem, but if it was being re-designed i think it would be a good idea. Cheers for the pcb's / shutdown controller - I'm having loadsa fun soldering all the components onto it now.

    Andrew
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  10. #10
    Maximum Bitrate eugenen's Avatar
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    Since were pulling very little current off the -12v line why not just put a 12.6v zener across the -12v line to cap it. A small zener diode (1A) should be fine. Ahh here we go, did a google for zener, fund this link http://hyperphysics.phy-astr.gsu.edu...ids/zener.html
    middle part shows a simple regulator ckt. zeners are basicaly what is inside a linear regulator, but the linears have extra stuff added. Notice that since a zener operates in the reverse voltage side, it is connected so it appears backwards in this ckt. Basically you want it to not conduct (block) currnet. When the voltage goes over its rating it will conduct shorting the extra to ground. (very un-scientific explanation there). Since we want to regualte negativge voltage we just need to reverse the diode.

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