MXR noise gate no output

[Sinster]

output sound only in bypass.

Using tonepad schmetic http://www.tonepad.com/getFileInfo.asp?id=77 and offboard wiring schematic http://www.tonepad.com/getFile.asp?id=76
Ordered all parts from MOUSER, followed schematics except for the 47pF cap used a .047uF, no other hacks/modification were performed.

Using a Fluke 189
Battery - 9.1V
Battery to PCB - 9.1v
Battery to ground = 0.0v

Q1
C = 9.1V
B = 4.366V
E = 3.745V

Q2
C = 3.825V
B = .420V
E = 0.0

Q3
C =4.367V
B = 4.417V
E =3.907V

IC1
P1=4.219V
P2=4.379V
P3=4.340V
P4= 0.0
P5=9.03V
P6=4.604V
P7=4.604V
P8=4.409V

Z1
A= 0.0
Z= 4.365V

[frokost]

Pin 5 should be half of the voltage on pin 8, not the other way around. IC pins are numbered like this:

1   8
2   7
3   6
4   5

Is that how you took your readings?

[Sinster]

No I took them as

1  5
2  6
3  7
4  8


Now this is what I'm getting

P5=4.401V
P6=4.596V
P7=4.596V
P8=8.99V = Battery Voltage

Thanks for the response.


I was checking the caps and that .047uF that I put in place of the 47pF is bad.  So I think I might have found my culprit.   It's reading 93.nF

[frokost]

Ok. Next: Q3 is a FET, so the pins are called Drain, Source and Gate. Make sure it's oriented correctly (google for the datasheet for your specific FET) and post back the voltages for D, S and G.

[Sinster]

Q3
D=4.363v
S= 4.364v
G=3.904v

[Sinster]

Does that look right?

[MikeH]

I don't think so.  It's possible that Q3 is either backwards or bad or you've taken the readings wrong.  Unless it is being used in a way that I'm not familiar with it can't operate with the voltages posted.

[Sinster]

placed it 180

Q3
G=4.145V
S=4.365V
D=4.365V

[Sinster]

Installed new 2N5485
in original configuration

Q3
G= 3.901V
S= 4.362V
D= 4.362V

[Sinster]

Is there anything else I can check?

[Renegadrian]

Sinster, I started today my Callate Gate 2 (that's the name on the tonepad file) - I noticed that cap, as you can see there is NO 47pF in the BOM or in the schem below the PCB layout. You may notice that some parts' border in the layout is orange, maybe that indicates additional optional parts, as it it the same with the pulldown 2.2M res at the input (you can find this one in the schem, but not in the BOM).
That cap maybe filters out some highs?! My guess here...but not sure...

[Sinster]

Sinster, I started today my Callate Gate 2 (that's the name on the tonepad file) - I noticed that cap, as you can see there is NO 47pF in the BOM or in the schem below the PCB layout. You may notice that some parts' border in the layout is orange, maybe that indicates additional optional parts, as it it the same with the pulldown 2.2M res at the input (you can find this one in the schem, but not in the BOM).
That cap maybe filters out some highs?! My guess here...but not sure...

2.2m and the 47pF did throw me  a little since it wasn't on the BOM.   Then I read a few of the build reports said they included them.   

Let me know how your build goes. 

[Sinster]

Also when I hook up a 9v PSU to it, I hear a thumping sound and it seems like it gets faster with a pot adjustment.  I Don't get the thumping sound with the battery.

[Sinster]

Removed the CAP and the Resistor not in the BOM and still not output.

[Sinster]

 

[oldrocker]

I have built many pedals and this had to be the most troublesome build to date.  I perfboarded this and couldn't get it to work for almost 2 months.  That was by far the longest debug of any project I had built yet.  When all was tried I ended up removing the dual op amp and replacing it with two 741 single op amps and it finally worked.  It was most likely a build mistake on my part but it was the only thing that worked for me.  The schem I used I found here posted by Aron I believe.  I just thought I'd mention that experience with you.

[Sinster]

Thanks I might have to try that.

[oldrocker]

Here is the schem I used.
www.diystompboxes.com/pedals/schems/MxrGate.GIF
Watch out for the pinout for Q3.  Many other schems I've seen had it drawn wrong.  This schem is correct.

[Mark Hammer]

Is that really supposed to be a momentary switch?  I owned one of these puppies way back when, and it sure didn't feel like a momentary switch.

[oldrocker]

I didn't use the momentary switch on mine.  I didn't even install a bypass circuit.  I planned on leaving the gate engaged always.
I assumed the switch was used as a temparary gate shut off when you wanted a note to ring out in the middle of a fast solo where it might be more natural to lift off then to push the stomp switch again to turn it back on.  Other then that wouldn't it still need a bypass switch?  I never owned one these so I don't know.