Completely dead - no sound whether engaged or not
This is actually a blessing in disguise. Almost all of these problems are
power problems of one kind or another on any effect that ever worked.
In order suspect
Broken wire or part - Replace it.
Go to the Audio Probe if it's got good power and grounds, and no obvious
Using a voltmeter, measure your battery or power supply and verify that it is
indeed putting out the right voltage. One dead battery can eat a whole day
of debugging! Connect the (-) or black lead of the voltmeter to the (-)
battery terminal and the red or (+) lead to the positive one. Expect a
battery to show a little more than the "nominal" voltage when
really fresh, a little less when it's partially used, and a lot less when
discharged. For instance, a fresh "9V" battery is often 9.5 to
9.9V; a moderately used one is 8.5 to 9.5. If it's under about 7.5V, your
results can be affected badly by the low voltage it puts out.
Connect the power source to the board. Hook your voltmeter (-) or black
lead to signal ground, and start measuring power supply voltages. First, measure
the voltage where the battery wires come onto the board. If the battery
measured good before you connected it, and it now measures a very low or
zero voltage, you know that something on the board is pulling it down. You
may have a short in your wiring or a bad component.
It's quite common for a polarity protection diode to short. Be suspicious
of these if you have a power problem.
Another problem is when the ground side of the power is switched by an
input or output jack. If this is not making good contact, you don't get
Measure the voltage at the power pins of every IC to be sure DC power is
getting there. If it's not, flip the board over and use your voltmeter
lead to trace the wiring from that IC power pin back toward the place
where DC power comes on to the board. Find where the power starts being
good, and you just crossed over the break in the line.
If you have good power and the "ground" or -V pin on an IC is
not at zero volts, use your voltmeter lead to trace the "ground"
line back to where it starts being zero volts again. Once more, you just
crossed the break.
Remove the power source or battery. Switch your meter to ohms, connect the
(-) or black lead to signal ground, and verify that every single place off
the board that
is supposed to connect to ground actually does - including pots, jacks,