Troubleshooting with a DMMIf you have a digital multi meter (DMM) and have some idea of how to use (or not), you can take some readings to see if things measure up correctly.
First up is continuity tests. If you have no idea what that is, here is a tutorial:
http://www.ladyada.net/learn/multimeter/continuity.htmlBasically, you set the meter to continuity, and it will beep when the connection you are measuring with the DMM leads is good, or has no resistance across it.
Here is a pcb map showing the ground connections:
Attachment:
CB Ground Map.jpg [ 215.39 KiB | Viewed 22553 times ]
So, both sleeve connections, the 'Black' pad, the bottom ends of R2, R4, and R5, pin 4 of the op amp, and the right side terminals of the trim pot should all connect to ground. To measure this with your DMM, set it to continuity, touch the two probes together to make sure the meter beeps, clamp the black probe to the sleeve lug of one of the jacks, and use the tip of the red probe to test for continuity at each of the points mentioned above. If you find a connection that is not getting continuity to ground, resolder that connection and try again.
Next up is supply voltage, referred to as V+. for this we will be measuring voltage, not continuity. Again, here is a tutorial:
http://www.ladyada.net/learn/multimeter/voltage.htmlYou basically set the meter to DC voltage, clip the black lead to a ground point, like the sleeve lug of a jack, and use the read lead to touch components and record that reading. Here is a pcb map showing the components that connect to V+:
Attachment:
CB V+ Map.jpg [ 206.3 KiB | Viewed 22547 times ]
The 'Red' pcb pad, the bottom and top side of the diode, the positive side of C4, pin 8 of the op amp, and the bottom sides of R1, R3, and R6 should all have the same amount of voltage that you measured on the top side of the diode. The bottom side of the diode and the 'Red' pcb pad should be about one volt higher than the rest of the readings. Also, the bottom side of the diode and the 'Red' pad tell you how much voltage your battery is currently putting out. So, if you have less than about 7 volts there, you should probably try a fresh battery! My build has 8.96 volts at this point.
Other VoltagesHere are some other voltages you can check to make sure your build is working properly:
Pins 1 and 2 of the op amp should have about 1/2 of V+ (4.5 volts if you read 9 volts at the stripped end of the diode). (my build has 8.33 volts on the stripped end of the diode and 4.18 volts on pins 2/3)
Pin 3 of the op amp should have slightly less than 1/2 of V+. (my build has 3.81 volts)
The emitter of the transistor (E pad) should have about 1 volt or so. (my build has 0.98 volts)
The base of the transistor (B pad) should have slightly less voltage than the emitter (about 0.2 volts less). (my build has 0.69 volts)
The collector of the transistor (C pad) should have about 2/3 V+ (6 volts of you have 9 volts V+). (my build has 5.56 volts)
Again, if you have any questions at all, please ask in a separate post and we'll answer you as soon as we can.
Thanks!