My noise gate is not gating

[whomeno]

Built a mxr noise gate. it seems to work but it dose not cut any sound at all.
built from here.
http://tagboardeffects.blogspot.com/2013/01/mxr-noise-gate.html
I used 3904's matched 1 number apart.
Ic is 4558
power input is 8.79

ic
1  1.79
2  1.65
3  2.30 to 3.0
4   0
5   2.91
6  4.35
7  4.35
8  8.79

q1  3904
e  .58
b  -.15
c  0

q2  3409
e  1.48
b  1.21
c  8.79

q3  2n5485
d  2.30 to 2.50
s  1.76
g  0

pot is wired correct



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[thermionix]

Trying to follow the cuts requires "upside-down and backwards" thinking.  Obviously your voltages are off on the 4558 and Q1 at least.  Do you have a schematic?

[Slowpoke101]

Q1's voltages are odd but have a look at Q2 - Its base voltage is very low so check what voltages are available on the 470K resistor going to it. One lead will show the current base voltage but the other lead should be above 4V. Measure the voltage across the zener diode, it should be the same as the 2nd lead of the resistor.
Please post your measurements.

Also the Tonepad Callate Gate 2 circuit suits this layout.

[whomeno]

http://tonepad.com/getFile.asp?id=77


4558
1  1.42
2  .92
3  1.31
4  0
5  2.90
6  4.32
7  4.32
8  8.75

q1 2n3904
e  0
b  -3.82
c  .74

q2 2n3904
e.80
b  .94
c  8.714

q3  2n5485
d  1.88
s  1.40
g  1.34

forgot to tun  it on the first time

1.19 at base
1.79 other end
1.79 top of diode
0 at bottom

[Slowpoke101]

OK. The Vref (approximately 4.5V but can be anywhere from 3 to 5.1V) is very low. There is a 22K resistor to the left of Q2. May sure that the top lead is at 9V. Its lower lead will be the same as the D1 cathode voltage. If there is 9V, good. If not check for a bad solder joint.
Now follow the track the D1's cathode is soldered to. Make sure that there is nothing connected that should not be.
A negative voltage on Q1 base is extremely odd - are you certain that that measurement is correct?

[whomeno]

22k top lead 8.75
bottom lead 1.41
yes neg
track is ok

[whomeno]

reflowed bottom of board

q1
e  0
b  .56
c  4.69

q2
e  8.74
b  3.13
c  3.93

q3
d  3.60
s  4.76
g  4.75

ic\
1  8.19
2  4.45
3  4.45
4  0
5  2.91

6  4.33
7  4.33
8  8.74

I think we got it this time
I just checked it when i have the tube pedal on with static, turn gate on turn it to 10 still have static

[Slowpoke101]

Pin 1 of the IC is very high. Make sure there are no shorts on its track.
The other voltages are looking better.
The operation of the sensitivity pot is backwards to what you would expect. Full clockwise rotation is actually minimum. You rotate it counter clockwise until the background noise (hum, hiss) disappear. When you play a note the gate should now open to allow the signal through.

[whomeno]

found the short pin 1 1.44
Thanks
checked at 0 still static if i go to 10 loud sqeal

[Slowpoke101]

OK. Now does this thing work?
and what are the voltages now found on the IC?

[whomeno]

ic
1  5.60
2  4.05
3  4.76
4  0
5  2.90
6  4.33
7  4.33
8  8.75

q1 
e  0
b  .46
c  4.72


q2
e  8.75
b  3.12
c  3.91

q3
d  3.83
s  4.76
g  4.76

[Slowpoke101]

The squeal is most likely caused by the wires going to the sensitivity pot cross-talking to the input jack and wires. Move the wires around and see if the squeal can be tamed. Shielded wires (coax) are sometimes needed.
If there input signal is too high in level the gating function (muting) cannot work. Feedback can cause this and the squeal is a sign of feedback.

[whomeno]

ok will play with it a while and see what it will do.
Thanks

[duck_arse]

in your build pic - 4 rows up from the bottom is a 2M2 resistor. it appears to be one hole out of its designated position. check against the two black spots.

[Slowpoke101]

Duck is quite correct with that 2M2 resistor - Good eye.
However there is also another problem. I know that the layout has been verified by others but there is a layout error and it too is to do with the 2M2 resistor.
One end of that resistor goes to the input track and the other end is supposed to go to ground. It does not. It is actually connected to the junction of the 680R (now 4K7) and the 1uF next to pin 1 of the IC.
Refer to the picture below. Move the lower resistor leg as pointed out by Duck to where it should go and move the upper leg of that resistor to the hole two holes above where the lower leg now is. That track is ground. Refer to the picture below;



This may calm down the squealing problem.

Usually people have trouble getting the MXR noise gate clones to work. But their problems usually relate to trying to get the gate to un-mute. The JFET is usually the problem but the solution is simple - change the 5V1 zener to a 6V2 zener. This ensures that the JFET's gate voltage will go sufficiently lower relative to the source voltage, turning the JFET off.
You may need to change the 1M resistor that you changed to 1K8 back to 1M to get proper gating action.

[whomeno]

made the change to the 2m2
nothing but static with pedal on or off
changed 1.8k back to 1m, still the same

[Slowpoke101]

Challenging things aren't they?
Hopefully the squeal has now gone or nearly gone.
One other thing to do layout-wise is to reverse the 10uF capacitor to the right of the JFET.
Do a quick test and see if it works - If not, go to the next step.

Now to find out if the thing can actually mute - To force it to mute short the JFET's gate and source together. A drop of solder on the socket pins (solder side of board) will work.
Does it now mute?
If it doesn't, remove the JFET and rotate it so the flat side faces Q2. If it now mutes, remove the solder short and see if the gating effect now works.

[whomeno]

ok the main reason I need the gate is for the  dual valvecaster. if I run both gains at full, I get a lot of nosie,when not playing just holding strings.
I thought gate was working but it don't seem to make a differance from 0 to 10. am I asking to muich from the pedal or is it not working right yet?
Thanks for all the help so far. I wish I had half the knowledge you guys have.

[Slowpoke101]

The noise gate is meant to be used with guitar level signals. Your preamp may be a bit too high with its noise levels. Let's worry about that a bit later. The main thing is to see if the nose gate does work as intended.
So connect your guitar to the gate and then connect the gate to your amp (not preamp) and see if it will work.

Playing with electronics is the best way to learn about it but some study would be helpful. There are some very good books that you could read that may help with understanding. R.G (forum member) has written several very good ones. The one that I would recommend that covers most subjects but is very frightening is "The Art of Electronics". I think it was written by Horowitz and Hill.

But ask questions. There are quite a few very knowledgeable people here on this forum and most can explain things more clearly than I ever could.

[whomeno]

gating works like a charm. had to turn 2n5485 180 and remove short