There are rules of thumb when trying to figure out why something does not function. The primary philosophy is to break the problem down and isolate what does work, from what does not work.

Ross Baldwin Jokes, if it ain’t broke fix it until it is… but seriously you must be deliberate and careful in tracing down where the problems lie.

1. Is it plugged in?
2. Is it turned on?
3. Check that power and ground is getting to each part of your circuit that needs it.

(Be careful when using multimeter leads not to accidentally short out your probe tip to other parts or the other probe tip)


4. Are power and ground reversed?
5. Are all connections you think correct actually correct? (Use your continuity test with your multimeter to determine that all connections are allowing signals and voltage to get through) I have built circuits multiple times to get them right and this is very much a part of this practice.
6. Are all components placed in the board with proper polarity? Check polarities again (capacitors, LED's, Diodes)
7. Use layout schematics and check off what you have placed on the board.
8. Are all components within the proper ranges and voltages?
9. Try changing out a component with an identical component and see if this works.
10. Is there a short on the board? Do you get a reading between power and ground?

Good practices to prevent above from happening when constructing your project:

11. When constructing a board use sockets for chips and other parts that may be damaged and need to be changed out.
12. Review the manufactures data sheets and when you order parts be sure to ask if they have specification sheets on the product that they can send, though most are available for free as PDF downloads at questlink.com. File these away when done with the project or keep an electronic copy.
13. Use a .1 UF capacitor from power supply of operational amplifiers to ground.
14. Use .1 UF tantalum capacitor in each digital chip across power and ground pins.
15. Test all components before installing on boards i.e. measuring resistors.
16. Use existing circuits as building blocks as both models and actual circuits.
17. Avoid placing heat sensitive components near components that get hot.
18. Leave room for necessary heat sinks.
19. All leads that carry household current must be insulated.
20. Circuits in which a current flow is suddenly switched off or on may emit radio frequency radiation that can cause interference in nearby radios and TV's and other circuits.
21. Use stranded wire for all connections that are not fixed in position (battery clip leads, etc.) Sue solid wire for fixed connections
22. Use connectors with gold instead of copper or tin for long-term removable connectors.
23. Insulate exposed component leads mounted close to other exposed leads or hardware.
24. The input and output sections of high gain amplifiers should be physically isolated from one another. Inductance between output and input may cause output to be fed back into input.