Pandora’s box no sound when on

Ericmc

Member
Finished the build today and get no sound when on. True bypass works and the led comes on as it should, but nothing else works.

A few notes: I switched c14 to 10n which is supposed to be the same as having the fat switch. I also subbed op07 chips in place of the lm308 chips. Don’t know that either of those matter, but wanted to mention it just in case. Also in the picture I had already clipped the ground power wire so I could take it out.

Any help is appreciated, first time trying to troubleshoot a build so really don’t know where to go from here. 4C06A7E6-C3A4-4BB5-A9AC-FCD74ED631DC.jpeg 967B88EC-C6A7-4D0C-B534-2E2F370E4CDB.jpeg
 
10u, correct. That was a typo. I was unaware that capacitor had polarity so I will check that.

I looked at this for 10 mins and never noticed the chip 🤦🏻‍♂️. Thanks for the help. Let me look at those two and hopefully that will fix it. I will report back!
 
First try a different 4558, sometimes running them backwards renders them useless. Then, if that doesn’t work, audio probe to see where you’re losing volume.
I will give that a go! Is there a thread on how to audio probe a circuit? I’m new to this so don’t really know how to go about that but willing to learn!
 
Take an alligator clip, clip one end to a 100nf cap. The other leg of the cap will be what you use to probe the circuit. Clip the other end to the tip of your output cable. Take another alligator clip and clip the sleeve of your output cable. Then clip the other end to ground in your circuit. Plug up your guitar to input. Start strumming and carefully probe the circuit and see where you get no sound or get very low signal. Make sure all your knobs are cranked you want to make sure you can hear the signal. You should be able to pinpoint where the problem is. Hope this helps.

FYI: if you have flux pooled on your joints it might sound like a low signal just make sure you wipe off the flux to get good contact between the joint and probe.
 
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To follow up, the volume pot does indeed work as it should. Same with the tone knob from what I can tell. The gain knob almost seems to be working in reverse, which seems odd. Switches work as they should. Unfortunately don’t have another 4558 chip so will have to wait for my next order to get one of those.

As far as audio probing goes, is there any specific order I should go in?
 
To follow up, the volume pot does indeed work as it should. Same with the tone knob from what I can tell. The gain knob almost seems to be working in reverse, which seems odd. Switches work as they should. Unfortunately don’t have another 4558 chip so will have to wait for my next order to get one of those.

As far as audio probing goes, is there any specific order I should go in?
Follow the schematics. I would start at input and probe all the way through the circuit, until you find your culprit!
 
To follow up, the volume pot does indeed work as it should. Same with the tone knob from what I can tell. The gain knob almost seems to be working in reverse, which seems odd. Switches work as they should. Unfortunately don’t have another 4558 chip so will have to wait for my next order to get one of those.

As far as audio probing goes, is there any specific order I should go in?

You can use a TL072 or NE5534 if you have any on hand. That part of the circuit isn't too fussy which dual is used there
 
You can use a TL072 or NE5534 if you have any on hand. That part of the circuit isn't too fussy which dual is used there
I just saw this, but the good news is i got my shipment of stuff in and with the new 4558, it is up and working! Thanks to everyone for the help! I am really liking this pedal so far.
 
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