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Re: [motm] power anomoly

2003-12-27 by Scott Juskiw

>What do you think?  My guess is the power supply goes into short
>protection during inrush.  The .71 vdc would be a normal forward
>voltage drop from the pass transistor, showing up in parallel at the
>shut-down side of the supply.  Anyone else, have something like this
>happen as they neared the limits of power?  Am I just going to pop
>for the next bigger (or greater!) supply?
>
>I summon the vast power of knowledge that is the MOTM Group!

This happens to me too. I have 6 cabinets, each with their own 900 
power supply. One of the cabinets will occasionally start up with the 
-15V line brain dead. This is immediately obvious because the 320s 
don't oscillate anymore (the LEDs stay lit at maximum green). I have 
to toggle the power to this cabinet a few times to get it to work 
properly. When it does start up properly, everything in that cabinet 
works fine. As you've noted, it looks like some kind of current surge 
at startup.

I rebuilt my cabinets recently and noticed that this problem went 
away completely when the number of modules in the cabinet was 
reduced. I can't pinpoint it to a specific module, only to the number 
of modules in the cabinet. As it stands now, if I remove power from 
any single module in that cabinet, the problem goes away entirely.

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