USA Big Muff misbehaving

[Shorty]

Hey all.

A friend of mine has an obsession with EH stuff that began with his USA big muff.
She's only about a year or two old, but something's not quite right with the poor lass. Usually it works fine for both 'bypass' and 'on', but occasionally when he stomps it on the volume is very low (half or less audible volume) and he has to stomp it off and on again, which usually sets it straight. I've taken it apart to check connections and they all seem cool, it just confuses me because as I said it only happens 'occasionally'.
Could the problem be the switch itself?
I've read the debugging thread and the article at Geo, but nothing there seems to point to this problem.
Has anyone seen similar problems with EH gear? Any suggestions?

Love you long time, Shorty.

[theehman]

Vintage or reissue BM?

[petemoore]

Could the problem be the switch itself?
  I've had that exact scenario caused by faulty bypass switch.
  As far as has that ever happened to an EH pedal, I would say yes because it is a pedal, not because it is an EH pedal...any pedal can get a glitch.
  Have you tested for continuity across the relevant lugs of the switch when it is in 'misbehave mode'?

[earthtonesaudio]

The order of probable causes of the malfunction goes like this:
1.Operator
2.Power
3.Mechanical
4.Component

...Since your buddy's used it for a year with no problems, you can probably rule out #1.  Next check the battery/power connections, then the switch and jacks.

[Shorty]

Vintage or reissue BM?

Reissue

  Have you tested for continuity across the relevant lugs of the switch when it is in 'misbehave mode'?

No, but I'll check that, thanks (I don't have the pedal atm)

I suppose I could replace the switch and either confirm or rule out that possibility. Thanks for the replies.

[cpm]

i've just replaced a faulty 3pdt from a EH AB box
these things happen