OCD Pedal with low volume

[kraigen]

I built an OCD clone, and it has en extremely low volume output; I already probed around the IC and pin 7 doesn't give a high volume output, but pin 1 does. Here are my voltages in the IC:

1: 4.34v
2: 5.16v
3: 2.54v
4: 0v
5: 4.29v
6: 4.35v
7: 4.35v
8: 8.65v

This is the schematic:
https://tornadoalleyfx.files.wordpress.com/2015/07/ocd_schem.gif

And the PCB layout:
http://3.bp.blogspot.com/-vlCPCaXt2Bg/V-KNR2AHCeI/AAAAAAAAEPo/xHUW87Y6RAobESgYdORP72ET2BCkOEjqQCK4B/s1600/Fulltone%2BOCD%2B2.png

[kraigen]

I just measured both MOSFETS and all of the terminals have a voltage of 4.3v, this seems a little fishy to me.

[Kipper4]

The mosfets are being used as clipping diodes.
You've probably made a wiring error or bad part placement.
Can you post some pictures please.

[kraigen]

The mosfets are being used as clipping diodes.
You've probably made a wiring error or bad part placement.
Can you post some pictures please.

I'll do that as soon as I get home (the pictures)
Meanwhile, do the voltages seem right?

[Kipper4]

The voltages seem ball park ish.
Pins 2 and 3 seem a little off but that could be meter loading.
Is it boxed? Did it work fine before boxing?
Rich

[kraigen]

I didn't have my test rig with me, it's boxed.

[kraigen]

Here are some pics of the pcb:

[GGBB]

I just measured both MOSFETS and all of the terminals have a voltage of 4.3v, this seems a little fishy to me.

That's to be expected - both ends should be at the "V1" voltage.

[anotherjim]

Amp pins 1 & 2 volts don't seem right to me - as if there's no feedback. Gain pot bad, cracked pcb track....

[kraigen]

Amp pins 1 & 2 volts don't seem right to me - as if there's no feedback. Gain pot bad, cracked pcb track....

I've checked both the pot and the tracks, and there is no issue there. However, I probed pin 2 and the audio is not good there, it has a stutter, for lack of a better word.

[anotherjim]

You may have too much gain. What value is R4?

Pin 2 should actually be silent, unless the output pin 1 is clipping.
Try temporarily shorting pin1 and 2 together. That makes is a clean x1 amp. You should hear a fairly clean sound then - a little boosted compared to bypassed.
If VR3 volume control is 100k, then output level is quieter than with a 500k pot.

[GiovannyS10]

Hey guys, i got the same problem using the same layout. The weird thing is i already used this layout for doing a OCD V3 and worked okay - Now i am doing a V4 and i got the volume problem. I checked that in pin 1 i have a huge good sound from the pin 1 until the gain pot lug 1, but in the lug 2 i have a too small volume sound. But obviously the pot is not the problem. I will check it more accurate this afternoon. Anyone has idea about what is it?
I just replaced the 1n34a for a 1n270 but i think it's will not cause me any problem.

[GiovannyS10]

Hey guys, i just disassembled my board and found two things that maybe caused the problem:
1. A couple of bad new fets. My couple of 2n7000 was in short, but both was new... So the circuit not worked properly.
2. Bad contact between the 47nF cap to the tone pot.
I did another board the reassemble the same parts (except the fets - this one i replaced for a couple of new ones) and everything worked as expected.

It was not the first time that i got bad new components. It happened with diodes before... So be aware to it, guys.

[nickbungus]

I had the same problem with mine, same layout.  Couldn't find anything obvious and now it lives in my circuit graveyard.