EVH Phase 90 - not working

[Semperfidoe]

Hi again.

Today a friend who's in a band told me his EVH phase 90 stopped working. The problem is this.

Pedal connected up but not switched on - signal passes through fine.
Turn the pedal on - the LED lights up but there is NO sound. I dont mean just the effect - I mean NO sound whatsoever.

Unfortunately its surface mounted components so there's not many I can change if faulty. I wondered if it might be the footswitch - anyone any ideas - Ive heard of this fault before with these pedals but cant find anything on any searches ive tried.

Thanks in advance.

[jaysg]

Start simpler...check for a dead battery, broken wires, a bad switch and an open pot.

[Semperfidoe]

Checked the battery/psu so its not that.
No broken wires (there arent any its surface mounted - only wires are to battery and its the same fault whether a battery or psu is used)
Probably a stupid question but how do I test for the switch/pot? (these are what I suspect naturally). Tried basics with my multi-tester but might be checking the wrong way

Thanks

[kusi]

hi,

a long time ago, i had a phase90 with a broken transistor in the mixing-stage... maybe this helps...

regards,
kusi

[jaysg]

I'm afraid at this point, you need a scope.

[O]

Check both diodes that are next to the dc jack. If a reverse polarity adaptor is plugged in, the diode gets fried. I've had several MXR Phase 90's that had the same symptoms as you describe and in 90% of the time, the reverse polarity diode was blown.

[petemoore]

  AAlot of debugging can be done with a DMM on this, I've fixed phase 90 many times...long story why I used hard to solder to solid core wire.
  See the "Debugging Thread".