crybaby GCB95 eccessive loud pop when powered in

[anotherjim]

I don't get you, Antonis.

How does Cin1 see Q0 output impedance?

There is no antipop resistor. A DPDT should ground the input in bypass like this...

...and if it does ground the input and stomping on it causes a pop - surely has to be a different fault?

It seems that some don't believe the fault can be at the DC jack because it pops with battery power too, but the battery + goes thru a contact in the DC jack!

[antonis]

How does Cin1 see Q0 output impedance?

I was talking about CryBaby input cap C1..
(which definatelly sees Q0 low output impedance hence no issue with charging it ..)

P.S.
Different "input" cap term definition..

[ronh]

anotherjim, I will check the DC jack.  Its not the by-pass circuit and it does it on battery too.  But, if its the jack, should it do on every transition from by-passed to effect?  Never done it on the reverse.

[anotherjim]

As I said earlier, the 220uF power cap can hold enough charge to prevent momentary disconnection of the incoming power being heard. It's not a bad cap, it's just doing its job. So when you leave the pedal alone for a time that cap starts to discharge due to a high resistance contact somewhere and the PCB voltage slowly sags lower. Give it a shock and the connection makes better, the cap charges up rapidly and the voltage shoots up causing a pop noise. That's one scenario.

That DC socket has a hard life, it only has its contact pins soldered in the PCB to secure it. Not good practice IMHO, but we are where we are.

[Mantra]

As I said earlier, the 220uF power cap can hold enough charge to prevent momentary disconnection of the incoming power being heard. It's not a bad cap, it's just doing its job. So when you leave the pedal alone for a time that cap starts to discharge due to a high resistance contact somewhere and the PCB voltage slowly sags lower. Give it a shock and the connection makes better, the cap charges up rapidly and the voltage shoots up causing a pop noise. That's one scenario.

That DC socket has a hard life, it only has its contact pins soldered in the PCB to secure it. Not good practice IMHO, but we are where we are.

hi
i have recently replace it ( 220uF power cap) , no luck
the strange thing , i get another GCB95 (brand new) it's my friend new wah wah  , "better truebypass" with 6 pin switch , no iusses at all , no pops
seeing i'm stubborn i will replace every caps and resistors , I have to find out the culprit
but on the net there are so many tutorials how mod + leds  , but there really few tutorials to do a clean job for a simple trubypass mod .
often the leds are culprit
even in the screenshot posted above and the stinkfoot tutorials have few information and small images
i would like to see 2 decent tutorials , not for me but for many users that are going to make the first mod
by the way , about my friend brand new wah , i have made an "incision" very light (without pushing hard) with "throwaway" knife very sharp , re-wiring in "better truebypass" ,
ps i have tried "Basic true bypass" no loud pop , just an audible pop but ok
and it's sad that only me and ronh have such issue , seeing seems hard to find a fix
thanks

[antonis]

In some cases, it's realy difficult to distinguish mechanical pop from electrical one..

[ronh]

Ok just an update.  I replaced the DC power jack.  Did not fix.  I suspect it will be a defective component.  I had one in an amp.  Measured good in every way but failed in circuit.  As this only happens after power up.  Will keep looking.

[ronh]

Another update.  I may have the problem solved.  On my pedal I measure 0.04Vdc on the blue wire coming from the board.  Leaky cap.  On the ElectroSmash schematic it is C5.  If it is this cap, then the first discharge path, effect on, would cause the pop.  The next device input resistance would provide a drain for this voltage. No?  Effect off, wait for charge to build, effect on again and pop.
I will change this cap out to prove this.  Mantra, if you are still following your post, measure the blue wire from the board.  Should be 0Vdc with a cable plugged into the input.  If it is this cap, a low cost fix.

[anotherjim]

When to found that voltage leak, was anything plugged into the output? Film caps rarely fail like that (can happen though). The DC can be from what you plug in to, but it also ought to make the wah pot crackle a bit. You can test with nothing plugged in the output jack.

However, if you had something like an amp with DC leakage to its input jack, you would notice with just a guitar plugged in as it makes the guitar volume pot crackle.

[Mantra]

Another update.  I may have the problem solved.  On my pedal I measure 0.04Vdc on the blue wire coming from the board.  Leaky cap.  On the ElectroSmash schematic it is C5.  If it is this cap, then the first discharge path, effect on, would cause the pop.  The next device input resistance would provide a drain for this voltage. No?  Effect off, wait for charge to build, effect on again and pop.
I will change this cap out to prove this.  Mantra, if you are still following your post, measure the blue wire from the board.  Should be 0Vdc with a cable plugged into the input.  If it is this cap, a low cost fix.

Hi Ronh
yes i'm following your progress
very interestating , on my wah should be the cap c6
but I will test c8 too
may I which tester do you use ? I have a cheap one here
here my c6 cap with the red arrow and the c8 with a blue arrow , is my wah schematic like yours?
https://ibb.co/X2CRg5V
thanks a lot , really appreciate a lot

[ronh]

Hi Mantra, I have the same board. To see if you have the same problem, you will have to disconnect the two blue wires that go to the switch.  One blue wire will go to the pot, the other to the circuit board.  You will measure the wire going to the board for a small dc voltage.  Black meter lead to ground. I used the ring connection on the output jack.  The red meter lead goes to the long blue wire.  Make sure your hands are not touching the wire or ground.  Your meter should be on dc voltage, low level.  Hold for a minute, should show zero.  If it is zero then it might be the other cap.  Then you would have to measure the yellow wire going to the pot.  As the blue wire is easiest to do, do that one first.  After measuring you can re-install the two blues wires back onto the switch

Or you can just replace C6 and C8 on the board. Faster and easier.  FYI, if your replacement caps are bigger, there is another hole connected to one of holes in use now.  So a bigger cap can be installed.  You will need a 0.22 uF, 25volt or greater film cap.

I am waiting for my replacements.  If you replace and it fixes, please post the result for others.

[Elektrojänis]

Damn. I anwered something without realizing there was another page in the thread, so forget about this message.

[ronh]

I swapped out C6 & C8 and the problem is gone.  No pop.  Just posting this for the bots should someone else have this same problem. 

[Mantra]

I swapped out C6 & C8 and the problem is gone.  No pop.  Just posting this for the bots should someone else have this same problem. 

Hi @Ronh

great find!!!!
sadly i had to time to try to replace , but will do
in short you have replaced c6 and c8 caps with caps with same value ( 0.22 uF) but with 2 film caps (25volt) ?
does the wha tone changed?
again great find Ronh
thanks Rohn