Physics 140  Troubleshooting/Debugging Hints

 

1. Be sure the multimeter is set to read what you expect.

 

2. If you are using a scope be sure the settings are correct for what you are measuring, i.e. AC/DC coupling, triggering, active inputs, vertical gain, time base, trace intensity, etc.

 

3. Check power supply voltages at the supply.  Try it with and without your circuit attached.  If it is bad without your circuit attached, you need a new supply.  If it is bad with your circuit attached, you have a problem with your circuit -- fix it before you reconnect the supply.

 

4. Check voltages at the circuit to be sure you are getting what you expect at the right places.

 

5. Be sure your wires are wires and not spark gaps.  This applies to all wires including scope and multimeter leads.

 

6. Some resistors have not learned the color codes, especially the tolerance portion.  Trust the ohmmeter if there is a discrepancy between the color code and the measured value.

 

7. Be sure the wires connect things you think are supposed to be connected, and don't connect things that shouldn't be connected (this includes the bus bars on the circuit boards).

 

8. Be sure what you think is supposed to be connected is really supposed to be connected.

 

9. You may need to make the circuit aware that you know what you are doing.  Forcefully reciting Ohm's Law is often effective.  Be sure you have it right -- it's in the lab #1 notes if you want to check it.

 

10. Sometimes a gentle blow to an offending piece of equipment will help (e.g. a 3 foot drop onto a concrete floor).  Because technique is best left to the professionals, please tag the piece of equipment, indicating your name, the date, and why you feel this treatment is necessary.  Our professional staff will be able to determine the proper positioning for the gentle blow.