Why does my Rebote have 18mV DC on the output?

[theundeadelvis]

Just finished up a Rebote 2.5. It sounds good except for switch pop (on and off). After removing the led completely, trying a new switch, and double checking cap polarity, I checked the voltage on the output and there's 18mV. What could cause this? I'm assuming it's the likely cause of my popping. I checked the polarities of all the caps and they are correct. Could one be bad? Thanks in advance!

[theundeadelvis]

I just replaced the cap on the output, and it's the same (actually a tad higher)?

[John Lyons]

There is a 100K resistance from ground at the output.
Any DC should be sent to ground though that resistor.
If the cap is correct for polarity and even if it leaks some DC it should not pop.
I guess you could make sure that the 100K is grounded maybe reflow solder at both ends.
Does it pop going into delay mode or into bypass?

john

[mth5044]

What if you soldered a resistor (100k?) across the two lugs of the out jack? I've seen that as a cure for the bypass popping, but I dont know anything.

[petemoore]

  That'd work...all the time...adding a load to the signal when in bypass.
  That loading is generally preferred as being 'inside' the bypass route.
  'Adds' means that. If you put pulldowns on the jacks, the signal loading adds up.
 

[theundeadelvis]

I'll give it a shot. I checked the 100k and the jumper to ground and it was fine. I'll put another across the jack lugs and see what happens. Thanks!

[theundeadelvis]

Well, I tried a 100k and a 1M across the output jack lugs, and it still pops. 

[petemoore]

I'll give it a shot. I checked the 100k and the jumper to ground and it was fine. I'll put another across the jack lugs and see what happens. Thanks!
 No thanks necessary, I misled you.
 I was trying to explain accumulative signal loading...resistors in parallel which connect the signal path to ground, bypassed or not.
 You don't want signal loading IIUC.
 To pulldown the output capacitor to ground, a large resistor provides a small path for these charges to dissipate, when signal is present / if the pulldown resistance is large enough, you don't notice.
 If say you have 2 boxes with 100k's across all the jacks, that becomes 25k load on the SP.
 Put the pulldowns on the 'circuit side' of the bypass switch, so that when bypassed, these pulldowns are also lifted from the signal path.

[theundeadelvis]

Ahhhh, I see now! Let me give that a try.

[theundeadelvis]

I tried resistor on the board from input to ground and output to ground with no success. Somehow it's a little better now though (without the added resistors). The voltage has dropped to about 13mV? Frustration is mounting and I may have to walk away from this pedal for a while.

[theundeadelvis]

So now I'm noticing there is DC on the jack when it's bypassed too. Would this indicate a switch issue? I tried a different switch with no luck. I also notice the voltage fluctuates between 9mV and about 22mV.

[theundeadelvis]

Couple thoughts I had.

Could the 51pF(I subbed 47pF) ceramic cap have any affect on this pop?
Could a microphonic component cause this (it sounds almost like the mechanical thump of the switch amplified)?
Where else should I look?

Thanks as always!
Ahren

[John Lyons]

The ouput is tied to ground through that 100K so that is your pulldown resistor, no need to add anything there.
The PF cap won't affect the pop.(unless is microphonic somehow)
Is the board or anything else in the box microphonic?
Tap the switch, board, jacks etc with a hard object, do they ring, ping, thump or bump...they should not at all.

I had a bad cap once or twice that made a racket when the switch was clicked.
The switch just clunked the bad cap and made a ringing noise audible.
Ceramic caps are notorious for going microphonic.
If you can hear tapping amplified it's almost always the ceramic ones...

The Jacks are hardwired together in bypass so any DC (in theory) isn't coming from the pedal.

john