30
1.
Make sure your pedal has power. This not only means connecting a fresh 9V
battery or 9VDC 2.1mm negative tip power supply. This also means plugging in
a cable into the input jack. Don’t forget that the input jack acts as the power
on/off switch.
2.
Set your DMM (digital multimeter) to read DC Voltage for at least 9 volts.
3.
Connect the black probe plug to the COM terminal of the DMM and the red probe
plug to the to the Volts/ohms terminal of the DMM. Here’s a link to a YouTube
video on how to use a DMM
https://youtu.be/XRFtlUn4eBg
4.
Now you are ready to take voltage readings. Touch the black probe to ground.
The sleeve or either jack is a good ground point. Touch the red probe to the
various test points show in the following diagram.
The following voltages are based on 9.0VDC supply voltage. Your voltages may vary by
a few mV depending on your exact supply voltage. There is a ground pad just to the right
of TP1. This is also a good place to put your black probe
TP1: 9VDC
TP2: 8.9VDC or just slightly less than TP1
TP3: 4.5VDC or about half of TP2
You’ll notice that there are numbers around the op amp. Pin 1 is in the upper left corner.
The numbers go around counter clockwise to pin 8 in the upper right corner.
Pin 1: N.C. (no connection)
Pin 2: 4.5VDC approximately
Pin 3: 4.5VDC approximately
Pin 4: 0V (ground)
Pin 5: N.C.
Pin 6: 4.5VDC approximately
Pin 7: 9VDC
Pin 8: N.C.
If you’re LED is lighting, then you should be reading 9VDC at test point 1. If not, then
you are probably doing something wrong with your DMM.
If you are not getting 9VDC at TP2, then you likely have a cold solder joint at the
R6/100ohm resistor, or you have the wrong value resistor in that space.
If you are not getting 4.5VDC at TP3, then you likely have a cold solder joint at R7/22k
and/or R8/22k or you have the wrong value in one or more of these spaces.
If you are not getting approximately 4.5VDC at Pin 3, but you are getting 4.5VDC at
TP3, you’ve likely got a cold solder joint at the R9/470k resistor.
Summary of Contents for Gray 1976
Page 7: ...7 This is what your Gray Overdrive should look like when you are finished...
Page 19: ...19...
Page 24: ...24...
Page 25: ...25 Installing the ICs and Finishing Up...
Page 27: ...27...
