Wierd power / grounding issue - GC Chimaera

[eldanko]

Ian,

Did you ever figure out what was causing this? Just had a build for a friend brought back to me with - sure enough - a blown 9v1 diode. Took the MAX1044 with it by the looks of things.

The friend claims he had it hooked up to a Voodoo Lab ISO5 9v tap.

[midwayfair]

Ian,

Did you ever figure out what was causing this? Just had a build for a friend brought back to me with - sure enough - a blown 9v1 diode. Took the MAX1044 with it by the looks of things.

The friend claims he had it hooked up to a Voodoo Lab ISO5 9v tap.

The problem with a 9.1V Zener is that it has 5% tolerance, and most power supplies -- and new batteries -- run slightly above 9v (my one-spot idles at 9.43v, which is close to a new battery). A 10v might be safer, and it's still no where near the 12v that would fry the MAX. The fact is a Zener is not a regulator and never will be. There is a little circuit called a Zener follower that would be much better and would act a LOT like a regulator without as much voltage loss, you might want to look at that if you're repairing it and have room in the enclosure.

I think your friend might be mistaken about where he plugged it in, though. Ask him if he heard a high pitched whine climbing in frequency before the pedal stopped working.

[Scruffie]

Ian,

Did you ever figure out what was causing this? Just had a build for a friend brought back to me with - sure enough - a blown 9v1 diode. Took the MAX1044 with it by the looks of things.

The friend claims he had it hooked up to a Voodoo Lab ISO5 9v tap.

The problem with a 9.1V Zener is that it has 5% tolerance, and most power supplies -- and new batteries -- run slightly above 9v (my one-spot idles at 9.43v, which is close to a new battery). A 10v might be safer, and it's still no where near the 12v that would fry the MAX. The fact is a Zener is not a regulator and never will be. There is a little circuit called a Zener follower that would be much better and would act a LOT like a regulator without as much voltage loss, you might want to look at that if you're repairing it and have room in the enclosure.

I think your friend might be mistaken about where he plugged it in, though. Ask him if he heard a high pitched whine climbing in frequency before the pedal stopped working.

It's not an over voltage issue, the zener should be good for any voltage discrepency a '9V' supply/battery puts out.

The zeners here are burning out from over current as i've said, they're just pulling too much and shorting or opening. It needs either a current limiting resistor or the better option, to just be left out, a series 1N400X diode would be a much better solution, protecting from polarity and dropping any supply by 0.6V to keep the MAX below the 10V threshold (which Frequency Central proved several times can be gone over anyway... even if it's not good practice).