[sdiy] The Next Newbie Power Supply question...

[John L Marshall]

The Next Newbie Power Supply question...+S must be connected to +5V and -S must be connected to GND preferably at the load but okay at the power supply.

See if the transformer primary has an internal short to ground.

A 1A fuse in the primary implies that the power supply can draw upto 120 watts. At 50% efficency 60 watts for load. Plenty.
  ----- Original Message ----- 
  From: Rhen, Kris 
  To: 'SynthDIYmailinglist ' 
  Sent: Monday, December 10, 2001 2:43 PM
  Subject: [sdiy] The Next Newbie Power Supply question...


  I've got a +-12v, +5v regulated power supply which is acting odd (or more likely I just don't understand what's up with it).  Wired it up to take AC through a standard plug, one of the non-ground leads goes through a fuse (in this case a 1A fast-blow fuse, even though the supply goes to 1.5A I'll never draw that much from it).  The other end of the fuse, as well as the other non-ground lead from the input goes to the supply.  I take the ground and connect it to the case as well as the GROUND output lead (of which it has two)  Power it up as-is and its great, I get my +12v, -12v and +5v relative to the ground just fine.

  Now I run some wires from the GND, +5, +12 and -12 to a power dist board and power it up with a switch on a power strip its plugged into.  Fuse blows with a nice flashy lightshow.  I've gone through a couple of fuses like this (note NO LOAD (Doepfer/As/AS modules) yet - and I won't until I understand why they're blowing).  Note its outputs are

  -12v   GND   +12v   +5v   +S   -S   GND 

  and I don't have the sensing hooked to anything.  

  Can anyone tell me (without shouting :-) why the fuse is blowing?  Again, gotta learn somehow and you all have been great teachers.  Thanks again

  KRIS 



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