MXR Noise Gate & Woody debug help

[Rick James]

Hello,
Just recently discovered this forum and it's awesome. So much knowledge to sink in.
Anyway, I've build two effects last week and I need help getting them running.

Tonepad's MXR Smart Gate:
   Project link: http://www.tonepad.com/getFileInfo.asp?id=77
I build it exactly as the layout suggested with no mods and yet I couldn't get it to work. All I get is the noise levels changing when turning the pot but no signal.

Here are the voltages I measured.
Adapter 11.38 (Declared at 9V. I know not the best Power Supply but it works)

IC
1 = 10.68
2 = 2.47
3 = 0.65
4 = 0.00
5 = 5.33
6 = 10.47
7 = 10.47
8 = 11.14

Q1
C = 11.20
B = 10.58
E = 2.5

Q2
C = 0.52
B = 0.07
E = 0.65

Q3
G = 0.55
S = 0.65
D = 0.65

Woody
   Project: http://hotfile.com/dl/56709054/1667f03/M._Hammers_Woody.pdf.html
Same exact thing as the Smart Gate except I get to sound at all.

Adapter 11.38

Before R1 the voltage gets around 5.5v and after R1 it drops very low (around 0.2v) which i think can't be right

LM1458
1 = -0.5
2 = -0.54
3 = 0
4 = -0.6
5 = 0
6 = 0
7 = -0.5
8 = 0.18

TL074
1 = 0
2 = 0
3 = 0
4 = 0.18
5 = 0
6 = 0.01
7 = -0.02
8 = 0
9 = 0
10 = 0
11 = -0.61
12 = 0
13 = 0
14 = -0.01

Now I've exhausted all resources and couldn't get them to work. From what I've read in the debugging thread the voltages don't seem right. Any help would greatly be appreciated.
Thanks a bunch.

[jasperoosthoek]

On the MXR:

Looks like you placed the zener diode the wrong way. It has to be placed 'backwards' to drop 5.1 volts. If it is placed 'forwards' it will drop around 0.7 volts. This is confirmed by the fact that pin 3 on the IC reads 0.65 volts as it is directly connected to the zener diode. This has the effect that the opamp can not work anymore. But don't worry it won't damage it. The inputs and outputs all have to be around 5 volts (same voltage as vb).

When I built the MXR noise gate I couldn't get the gating to work. It just passed the signal but didn't turn it off below the threshold level. The MOSFET (2n5485) I used was to blame and I had to change a resistor to get it to work. Apparently the switching voltage of the 2n5485 was just a bit different from the one in the original pedal. If this happens to you let me know.

[jasperoosthoek]

On the woody

You need a dual power supply to operate it: 9 volts and -9 volts. Also there is an error in the schematic: C2 is wired backwards. The positive lug of the C2 has to be wired to GND as it filters the negative power supply. In a short time (minutes maybe) this will cause C2 to fail and become a short circuit. The voltages look like there is a short somewhere. Are you sure you didn't connect one of the ICs backwards? They both have their supply voltages on a opposite pins meaning that if you reverse them it's like applying a negative voltage. This will normally fry these type of ICs. I have experience with frying a TL074 this way. I hope you used sockets, I always use them and I was happy I did that time!

Could you check the capacitor and use two batteries to connect to it? One battery needs the - connected to the -9v input and the + connected to GND, the other needs the - connected to GND and the + connected to +9v.

Good luck!

[Rick James]

On the MXR:

Looks like you placed the zener diode the wrong way. It has to be placed 'backwards' to drop 5.1 volts. If it is placed 'forwards' it will drop around 0.7 volts. This is confirmed by the fact that pin 3 on the IC reads 0.65 volts as it is directly connected to the zener diode. This has the effect that the opamp can not work anymore. But don't worry it won't damage it. The inputs and outputs all have to be around 5 volts (same voltage as vb).

When I built the MXR noise gate I couldn't get the gating to work. It just passed the signal but didn't turn it off below the threshold level. The MOSFET (2n5485) I used was to blame and I had to change a resistor to get it to work. Apparently the switching voltage of the 2n5485 was just a bit different from the one in the original pedal. If this happens to you let me know.

Well, I checked the diode and it seems OK. Could the IC be faulty.

[elkulon]

Hi, I tried to build the Woody, and it doesnt sound. I checked out about the Ics, and they're just ok. I checked about shorts, and I've found one, but fixed, and still there was no sound. I checked the polarity of polarized components, and most of them are ok. But the C2 is (as the scheme) in wrong way. So, the question is the next..:
Can I use a single power supply, connecting V+ to V+ of the board, and GND to the GND of the board (offcourse, fixing the C2 polarity/direction)?
I wonder if the C2/R2 combo will probably make the "dual supply" effect, as many other effect laying around internet...
Sorry if the question is a bit stupid, but I don't know too much about electronics...

[mr_deadmaxxx]

there is a woody around here in this site that utilizes only +9V supply and Gnd. I've built it and it works great.