Debugging an IC Big Muff...

[alex_spaceman]

I've put together an IC Big Muff as per this vero layout:



Only changes at this stage are that I'm not actually using the tone bypass switch as I didn't have any On/On's (R19 and R20 are in place but i omitted C13 and connected lug 2 of the filter pot straight to the volume) and i used two caps in parallel (100nF and 50nF) in place of the 150nF input cap.

I didn't have all exact values so I approximated a couple: 67k for R9 (originally a 62k), 8k for R13 (8.2k originally) and 100nF for C10 (instead of 120nF).

I found some schematics from AnalogGuru which indicate that the volume pot is 100k rather than the 50k found in the layout. Could that be part of the volume issue?

Each pot does what it should but all I get out of it is VERY low volume and fairly gated distortion. I did a little probing about and here are the readings... The power supply gives me 9.45v

IC 1 - JRC4558D

1 4.60
2 4.61
3 4.15
4 0
5 4.35
6 4.61
7 4.64
8 9.27


IC 2 UA741CN

1 9.07
2 8.57
3 9.27
4 9.10
5 9.09
6 8.58
7 8.66
8 0

Finally, here are a couple photos of the board:





Thanks in advance!

Alex

[weasle76]

Hi, I'm just a noob really, and I could be wrong, but it looks to me like your IC's are in the wrong sockets (741 where 4558 should be and vice versa).
Also, I think the 741 is oriented wrong - pin 1 should be pin 5.
And looking at the voltages, IC2 seems to have 9.1 volts on pin 4, and I think it should be 0 volts/ground.

Like I said, I am but a noob, and could be wrong on any/several/all of the above. Someone else might be able to confirm or otherwise, and add to it.

[alex_spaceman]

Ha, always the simpler things, isn't it?
The IC were in the correct sockets but IC2 was indeed upside down... Sings just fine now!
I'll go and hang my head in shame... Or rather, play a couple tunes on it..!
Cheers mate, sometimes you really need an extra pair of eyes to pick up these "little" things...!

[weasle76]

Sweet! Glad it's working fine, and that I could do something useful! (I'm normally very quiet on here, don't usually have much to contribute!)