Mod Thunderdrive Deluxe Owner's manual

Use this troubleshooting supplement to help:
Measure DC voltage test points to identify major discrepancies and locate problem areas.
(Keep in mind that the voltage measurements will vary slightly from kit to kit. The voltages you measure should be in
the same ballpark, but do not expect to get the exact same value.)
1
2
3
4
5
Test Point
Transistor Collector
Transistor Base
Transistor Emitter
Power
LED Anode (+)
Location Description Voltage Measurement Your Unit’s Voltages
3.1 VDC
0.6 VDC
0.0 VDC
8.9 VDC
2 VDC
Using a volt meter, connect the ground side lead of the meter to any ground point on the pedal.
One convenient ground point would be the output jack’s ground lug. The other volt meter lead will
be used to measure DC voltage at the test points listed above and shown in the drawing on the next
page.
-+
You must plug a guitar cable into the input jack when taking the voltage measurements
because the input jack is set up to disconnect power from the circuit when unplugged.

-+
1 2 3 1 2 3
INPUT JACK
OUTPUT JACK
1
5
MPSA18
4.7K
2M
B
E
C
OUTPUT
POT
DISTORTION
POT
104J
104J
1
2
3
4
5
6
7
8
9
820
BLK
RED
+
-
GND
DC Voltage Test Points
Guitar cable must be
plugged into the input
jack while taking voltage
measurements
3
2
1
4
5

-+
1 2 3 1 2 3
INPUT JACK
OUTPUT JACK
1
5
MPSA18
4.7K
2M
B
E
C
OUTPUT
POT
DISTORTION
POT
104J
104J
1
2
3
4
5
6
7
8
9
820
BLK
RED
+
-
GND
AC Voltage Test Points
(Distortion set to Max)
Guitar cable must be
plugged into the input
jack while taking voltage
measurements
120
mVAC
120
mVAC
3.5
VAC
3.5
VAC

Continuity Tests
-+
1 2 3 1 2 3
INPUT JACK
OUTPUT JACK
1
5
MPSA18
4.7K
2M
B
E
C
OUTPUT
POT
DISTORTION
POT
104J
104J
1
2
3
4
5
6
7
8
9
820
BLK
RED
+
-
GND
Guitar cable must be
plugged into the input
jack while taking voltage
measurements
3PDT Foot Switch
1
2
3
4
5
6
7
8
9
Switching function of the 3PDT switch. The solid line
illustrates an internal connection between terminals.
1
2
3
4
5
6
7
8
9
With your meter set to check continuity,
check the footswitch terminal continuity to
make sure it is switching correctly.
The effect is on when there is continuity from
terminals: 1 to 2, 4 to 5 and 7 to 8
The effect is bypassed when there is continuity from
terminals: 2 to 3, 5 to 6 and 8 to 9
With the footswitch set to effect-on terminal
continuity (as shown above), check for
ground continuity to make sure you have
proper ground connections between the
output jack’s ground terminal (GND) and the
following test points.
1. Terminal Strip Terminal #1 and GND
1
2. Transistor Emitter lead and GND
2
3. LED Cathode (-) lead and GND
4
4. Footswitch Terminal #5 and GND
3
5
5. Input Jack ground lug and GND