Author Topic: The Evergreen CRAP Power Supply thread  (Read 197 times)


The Evergreen CRAP Power Supply thread
« on: November 09, 2020, 07:43:10 PM »
Hello denizens, here's a rewrite of one of my buddy's problems:

Been using the mxr iso-brick for a couple years.

Just got the new ehx pitch-fork+. Had plugged it into a dedicated wallwart a week ago to tinker five minutes but tonight was when I actually plugged it into my board with the other pedals and the mxr psu. Was really looking forward to giving it a proper play.

Turned everything on, display flashed for a couple seconds, I remember that much. I sat back down after a few minutes of doing something else and noticed the pitch fork+ was completely dark. Wiggled/swapped the power cable, the standard stuff. Then out of a hunch I probed the power output on the mxr I had been using. Itís one of those variable outputs that can be set between 5v and 15v. I had it set to 9 and a half. Multimeter was reading 18v.

The pedal is now fried and not sure what kind of recourse he has. But any defective PSU ideas or experience with overvoltage? Would an current gen EHX pedal be fried by an overvoltage factor 2?

Oh, and happy Monday friends.

Rob Strand

Re: The Evergreen CRAP Power Supply thread
« Reply #1 on: November 09, 2020, 09:35:39 PM »
I guess any PSU can fail and produce high voltage.

The input of the ISO-Brick is 18V,  so if it's a linear supply frying the pass transistor could short input to output and then it will pass the 18V.     It's not that simple as the unit is isolating so I guess the 18V in is isolated but the isolated side for the variable rails could well be 18V.

The design of that unit supposed to have foldback protection so it would expect to handle shorts fairly well.

The type of fault that could fry the unit would be someone plugging the 18V supply (or some other supply) *into* the DC output sockets.    The ISO brick would have to be designed to handle that.

A faulty voltage pot, say an open wiper could very well cause full output.

Is he 100% sure it is the 9 to 15V output that is producing 18V?  Those things have a number of outputs all sitting next to each other and all different.   Some are actually 18V!   A few are 9 to 15V.

The ISO-brick manual has  a clause stating,
"Dunlop assumes no responsibility or liability for equipment damage
caused by misuse of the Iso-Brick Power Supply."

I guess it boils down to if the fault is due to misuse.   The clause doesn't cover unit faults under normal use.
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