Little to no signal coming from first gain stage of big muff op amp

[jdoughty]

Ok, so I'm working on the landtone fuzz, which is pretty much a op amp big muff kit. I have successfully built one, but this one is not functioning. I've made an audio probe and isolated that the problem starts right out of pin 1 of the 4558 IC. I've looked to make sure I don't see any bridges to ground, and I am running out of ideas.

9v: 8.6
IC1:
1:7.9
2:3.8
3:4.2
4:0
5:7.8
6:7.9
7:7.9
8:8.6

Ic2
1:2
2:4.7
3:4.4
4:0
5:2.5
6:4.5
7:8.6
8:0

IC1's voltages look crazy, but I'm unsure yet as to why...

[anotherjim]

Look for a possible short (solder) to the ground pour around the connection between the 56k and 150nF (154) on the way to the 4558 pin 2.

[jdoughty]

There's clear audio signal going into pin 2 of ic1. Where the signal becomes weak/sputtery/almost non existent is after the 330k/pin 1. I've tried replacing the opamp and it still is the same. I'll look again for a ground  connection.

[anotherjim]

There shouldn't be much if any signal audible on pin2 when it's working properly. But the signal shouldn't get through there anyway if the fault was due to a full short to ground on the input. It would have to be a partial short and that is usually caused by a bad input capacitor. It's rare for those caps to be bad that way, but it can happen. The only other common cause would be if you fitted an electrolytic input capacitor with the wrong polarity which makes a good cap act like a bad one.

Ah, maybe I see it in the picture - a blue electro cap where a film cap should be, and it's the wrong way around?
Why did you fit that?

[jdoughty]

I'll try switching it around. Trying to let in more bass frequencies as the op amp version sounds so much brighter by default.

[jdoughty]

I replaced it with a .2u film one but still got issues. I can now hear some signal all the way to ic2 but it's incredibly quiet. Each boost stage doesn't seem to boost the signal.

The voltages appear to have changed since I did my last check on the ics, which tells me I had some bad solder joints somewhere probably.

IC1
4.3
4.2
4.3
0
4.3
4.3
4.4
8.6

IC2
2.5
4.8
8.6
0
0
4.7
4.7
0

[jdoughty]

Signal at input cap: powerful
Pin 1 signal: powerful
Pin 2 signal: sputtery, like it's trying, but it only makes sound when the signal is REALLY strong
Pin 3 And 4 nothing
Pin 5: loud still
Pin 6: loud
Pin 7: strong but blown out, lots of lows
Pin 8: faint, but I image that's expected

IC2:
Pin2 loud
Pin 3: faint, again not unexpected
Pin 4 and 5: nothing
Pin 6: static that has guitar sound in it
Pin 7 and 8: nothing

[jdoughty]

I think my issue now is somewhere in the piece that comes off pin 6.
I checked the signal at each point of the diodes and the only point they had no signal was when it went to pin 6

[soggybag]

IC2 pin 3 seems way off. Fallow that up through those 820k and 1m resistors to Vcc. That should be like 5v at that junction.

IC2 pin 7 should be 9v. Check this and follow it back to the power supply.

Check that IC2 is oriented correctly?

[anotherjim]

The input capacitor in the design of 150nF gives bass down to 15Hz. If you need more bass something will have to be changed elsewhere.

The first opamp is an inverting circuit. You don't get a proper signal on the inverting input of this opamp unless something's wrong.
That signal makes it to the output pin is what matters. The circuit uses negative feedback via a feedback resistor to cancel signal on the inverting input. It's actually trying to keep the inverting pin voltage the same as the non-inverting pin voltage. The fact that the output pin voltage has to rise or fall to make it cancel is how it gets a signal on the output pin. If the opamp output signal is too large, it clips. Then it can't provide any more negative feedback control and a signal (distorted) will appear on its inverting pin.

The second opamp is a non-inverting circuit. The signal goes to the non-inverting pin. Now, you should have signal on the inverting pin too since the opamp is applying feedback there to follow the non-inverting pin signal voltage.

The voltages on the RC4558 are good now.
I'm not sure what's happened with pin3 of the 741. It can't really be 8.6v can it?
As soggybag just said, you may have the 741 in backwards. It's the right way in your picture above - but have you since changed it. It's easy to do when IC's are meant to face in opposite directions. Most designers try to keep them all the same way around.

[jdoughty]

IC2 is in the right way, but I measured pins wrong.
IC2:
1:4.2
2:4.2
3:4.2
4:0
5:4.2
6:4.2
7:4.2
8.8.6

[ElectricDruid]

IC2 is in the right way, but I measured pins wrong.
IC2:
1:4.2
2:4.2
3:4.2
4:0
5:4.2
6:4.2
7:4.2
8.8.6

Ok, that looks like a happy op-amp to me. The problem is elsewhere.

[jdoughty]

Ok... I know the problem starts after pin 6 from my audio probe. At that point the signal comes out but it is quieter and full of static

[soggybag]

IC2 is in the right way, but I measured pins wrong.
IC2:
1:4.2
2:4.2
3:4.2
4:0
5:4.2
6:4.2
7:4.2
8.8.6

Shouldn't IC2 pin 7 be 9 volts? Everything else looks good here. Your sure IC2 is a single op-amp 741?

[jdoughty]

Oh god it's been a day... Just realized that was IC1... I'm struggling with flipping the dang thing over and mirroring which of is which when I do.

Ok IC2 for real:
2.5
4.4
4.4
0
2.5
4.5
8.6
2.5

[jdoughty]

Wow... I'm a dope... I'll report back in a bit. Long story short I had the ice flipped in my head. Pin 6 is outputting a strong signal

[jdoughty]

Ok between the resoldering and replacing that film cap I'm in business! Thanks guys and sorry for the poor quality info. I gotta try to remember the IC orientation better

[jdoughty]

So final update before it goes in the pedal. The input cap is back to the 150nf stock one. I changed one of the 1uf coupling caps to 2.2uf and that absolutely adds a ton of low end. Last change was to turn the 100nf in the high pass to ground to 10nf giving it a mid hump. I love it. I can use it on my bass and have the boom I wanted and have a full bodied tone on my guitar with the tone knob on the other side!

[anotherjim]

Here's a tip...
Some IC sockets are difficult to see the pin1 indent with a lot of components close by and any silkscreen print on the PCB can be obscured too (or even wrong!). I use an acrylic paint pen to put an easy to see marker spot on the pin1 end of the socket. Sometimes I do it with the IC fitted and have a matching mark on both. I use yellow because white is always out of stock in the store.
As some chips are expensive and don't like being powered up backwards, I find the marking worthwhile and it also helps when testing pin voltages.

[jdoughty]

great point, last thing I need is to be out a chip because of a simple avoidable mistake. I'll have to get in that habit