Peavey HFD-2 Hotfoot troubleshooting (scheme attached)

[Geezer]

I have an original Hotfoot and it's my favorite OD

It has developed a loud "POP" when activated, but only the first time, then it's fine as long as it's left "on", but if left "off" for 15 minutes or so, it will POP again when turned on.

It's NOT the switch, which are known to be wonky anyway, because I'm leaving the onboard switch always "on" and bringing it in/out of circuit via a looper.

I suspect a cap is leaking, but not sure where the most likely culprit is....I don't want to just go in and replace all the caps, but would like help narrowing down where to start looking/measuring for a voltage leak.
I guess it could also be one of the J231 transistors(?)

A clue.....it does it whether the onboard switch is activated or not....IOW, even if the switch on the unit is off, and only the buffer is active, when the looper switch is activated, it pops.

Here's the schematic....any help appreciated ;-)

Geezer

[Ciaran Haslett]

C13 and C14 (both 2u2) are the only electros in the signal path involved with the switching.  C5 is the only other electro in the signal path at all.  Wouldn't hurt swapping out those 3.

[rocket88]

should put this in the requests area too. would make a nice new layout for the site.

[Geezer]

Ha ha....its already done! ;-)

These are a great Rat derivative with a tweaked EQ...more tube-like and "transparent"

http://tagboardeffects.blogspot.com/2013/12/peavey-hotfoot-distortion.html

[rocket88]

haha. never notice that it's there. i may have to add this to never ending build list.

[Geezer]

Problem solved, thanks to some tech help over at TGP.

I'm using the pedal with a looper to bring it in/out of the circuit and this caused the propblem....
The pedal design (this is an original 30y.o. unit) has a buffered input, so in normal use would always have the buffer "in circuit" when bypassed by the unit's on/off switch.
Because of this design, It does NOT have a pull down resistor at the input...it's not normally needed because the input cap would never have a chance to charge under normal use.
However, using the looper, it left the input "hanging" out of circuit and the input cap was charging, giving a loud POP when switch back into circuit.
A 1 meg pull down R to ground at the input made it silent again!

Something to think about if you build this and use it with a looper!

G