Tonepad Callate Gate 2 (mxr noise gate)

[pete74]

Hi all, this is my first post.    Searched for this topic and found a bunch of hits but nothing really seemed to help me, I'm hoping someone here can.

Firstly, let me say I've built a number of project kit pedals before from GGG or BYOC and honestly out of the 10 or so that I've done, I've never had an issue (and therefore don't have much in the way of troubleshooting skills either)

Anyway, this tonepad callate gate v2 PCB is assembled with the parts from smallbear's list, no mods (yet). 
http://www.tonepad.com/getFile.asp?id=77

When switched on, the volume reduces and when I turn up the sensitivity pot it gets distorted (no noticeable noise gate functionality at this point).

Have tried to trace it thru using an audio probe (not that I'm too sure of what I'm doing but hey...), and when I get to pin 1 of the IC (4558) the sound is very distorted, sounds from pins 7 & 5 are extremely quiet.
I've seen that measuring the voltage from each pin is what is usually asked for so they are as follow:

1 - 3.9v       
2 - 3.8v       
3 - 3.6v       
4 - 0v
5 - 3.8v
6 - 4.1v
7 - 4.1v
8 - 8.3v

So that's that... I've checked orientation of all caps and transistors (yes the gate of Q3 is in the right place based on the datasheet for it), checked resistor values and solder joints.   Pretty stumped at this point.   

Anyone have any suggestions that might be helpful?
Thanks in advance

[duck_arse]

hello pete, and welcome.

we always like to see photos of what you have built. and even if we don't like to see them, we usually ask for them anyway. clear pics (not way huge tho) of front and back, and off board wiring, please.

[blackieNYC]

What's up with the 8.3 volts? Protection diode?   Try a battery and get that up to 9.5 volts. Don't know how that thing will behave when the battery gets weak

[pete74]

Thanks for the answers guys..... I actually found the solution in an old post here.    Changing the 1M resistor on the gate of Q3 did the trick!   

[pete74]

What's up with the 8.3 volts? Protection diode?   Try a battery and get that up to 9.5 volts. Don't know how that thing will behave when the battery gets weak

Good point... was so concerned with everything else it didn't even occur to me!

[duck_arse]

awww, no pictures?

[pete74]

awww, no pictures?

Here ya go...  Epic fail on my layout.  Just kinda guessed at the space available, so my PCB had to go in at an angle.. but whatver...

[rankot]

What is the new value of your gate resistor? Did you change one going from Attack pot to gate, or another one going from IC1b to gate?

I am also having a problem with this build, there is some kind of distortion that starts with note decay. 

[Slowpoke101]

There are several modifications that can make this noise gate work a bit better.

The resistor you are interested in is the one going from the Attack pot to gate. The resistor should be 1k8 to 2k2.

Other mods that are a good to try are;

Replace the 680R resistor and 1uF capacitor (pin 2 of IC1a) with a 4K7 and 2.2uF
Replace the 1uF/NP capacitor connected to Q2 base and across a 100K resistor with a 10nf capacitor.
On the base of Q1 there is a .047uF (47nF) capacitor connected. Replace this with a 10nF capacitor.
Connected to that capacitor there is a 1K resistor. Replace this with a 10K resistor.
On IC1b pin 7 there is a 1uF capacitor (output). Replace this with a 10uF capacitor.

You may find that you are still having problems with gating noise (stuttering) on note decay. Try replacing the
5.1 volt zener with a 6.2 volt zener. If you try this you may have to change the resistor going from the Attack pot
to the FET's gate back to a 1M

It is best to get this thing to work BEFORE adding the optional external pots (Sensitivity pot should be connected,
of course). If you have installed them already, remove them and install the correct links. Make sure that Ra (150K)
is also installed. Not having those external pots connected will help to minimise any confusing issues arising from
incorrectly set pots.

I found most (if not all) of these modifications on this forum.

[rankot]

This is what I did: http://www.diystompboxes.com/smfforum/index.php?topic=82933.msg1112952#msg1112952