mxr noise gate debug help wanted

[peterg]

I used the Tonepad Callate Gate 2 scheme and made mods to it. I'm not able to post a liink at this time.

Issues:
The sensitivity range is very limited from 0 to about 50k reiistance
Note attack is scratchy

The mods are based on some of the Tonepad suggestions, its build reports and various other right ups.

Mods:
1m resistor between Q3 gate and Ra resistor
Replaced Ra resistor with a 500k trimpot for release control. Set at 150k
Socketed IC1a's resistor and cap but hhave found the speceed values are best

Readings:
Ic 1 5.01
2 4.45
3 4.45
4 4.94
5 3.16
6 4.72
7 "
8 9.43

Q1 c 9.42
B 3.23
E 3.94

Q2 c 3.68
B 0.42
E 0.00

Q3 d 4.98
S "
G 3.68

The trannies are 194 and 196 hFE

My thought is to replace the 500k sensitivity pot with a 100k pot and a 400ish K resistor to deal with the range issue

Any suggestions?

[peterg]

Anyone?

[PRR]

> I'm not able to post a liink at this time.

http://www.tonepad.com/getFileInfo.asp?id=77

Assuming your meter is a heavy load; Not seeing a problem with voltages.

Did you use a tested board or is this your own layout?

[DIMstompboxes]

Maybe i'm wrong but that IC pin4 has 4.94v?

[peterg]

>

Assuming your meter is a heavy load; Not seeing a problem with voltages.

Did you use a tested board or is this your own layout?

Paul - thanks for the link. I created my own layout. The effect is there but I seem to be having the same issue as others have had relating to the sensitivity range pot. I socketed the resistor and cap at ICa -2 as recommended on build reports and will fiddle with them some more.

Maybe i'm wrong but that IC pin4 has 4.94v?

Good catch. I'll double check. I may have transcribed from my hand written note incorrectly - or I could have a bridge somewhere.

[peterg]

My IC - 4 reading was wrong - the beer googles must have been fogged up!

I used a 22k resistor and a 10uF cap at iC - 2 which solved the sens pot issue. The device works well except for a click with each note played. I take it that is the gate opening. I've tried a number of FETs and they all have the same issue.

Any ideas of how to get rid of the clicking?

[DIMstompboxes]

Mate, did you replaced the 1meg on Q3 gate with 1.8k?  That one in the middle of the three 1meg , the middle one try to replace it.
What FET did you use? There are many issue regarding this noisegate but don't give up, you're just at ballpark.

[peterg]

Mate, did you replaced the 1meg on Q3 gate with 1.8k?  That one in the middle of the three 1meg , the middle one try to replace it.
What FET did you use? There are many issue regarding this noisegate but don't give up, you're just at ballpark.

I replaced the 1m resistor with a 1.5K so the output is at the right level. No issues there. I used a 2N5486 FET. It's the closest to the recommended 2N5485 that I could find. I tried other FETs I have on hand and they all do the job (with clicking).

My 2N3904s aren't quite matched so there are some decay issues but that should be an easy fix.

Just need to get rid of the click.

The Noise Gate certainly is the most written up on pedal I've come across!

[peterg]

https://www.dropbox.com/s/yrxsusxrwjeefk0/1.jpg
https://www.dropbox.com/s/yrxsusxrwjeefk0/2.jpg

Attached are links to the front and back of the original MXR Nosie Gate.

The cap connected to the FET's drain is shown backwards on the schematic. The positive cap leg is connected to the drain.

I'll switch it tonight. Maybe that will solve the click problem.

[DIMstompboxes]

Yes try to reverse the cap neg to the drain.
For what I know if I'm correct  FET drain/source are interchangeable, but the schematic call for what it should be.
5952 need you to flip 180 degree I think, but yours is 5486..just try to reverse the cap polarity as you said maybe that it. give us an update mate.