I was looking at some of the very expensive test equipment used to troubleshoot circuit boards and it seems that they all use the Huntron type of testing. Injecting an AC signal and then viewing the results on a screen and then comparing that to a working board. Equipment made by Polar, ABI, QMAX, and it seems most of the people who make industrial test stuff where you place the board under a bed of nails type test fixture. My questions is, is this the only method that us used to troubleshoot complex pcbs? If so is there a good web site that covers the details of how this is done? I guess there are many variations on this method but none of them are perfect? are they? Even with one of these systems and a known working board can you still be unsure of what is exactly wrong with the board? And... Are there any other radically different types of systems used to troubleshoot complex circuit boards and how might they work? Thanks for the info Russ
Hi Russ, The Huntron testers are used to manually troubleshoot a circuit. They can be used on very simple or very complex circuits. The trick in using those testers in knowing how to interpret what you see on the CRT. The necessity of having a schematic varies, depending on circuit complexity and your skills. On a very complex circuit, especially one with lots of SMD components, it's almost mandatory. On average, Huntron testers are inexpensive when compared to state-of-the-art equipment from Agilent, Tektronix, IET, etc. Some of those instruments can cost upwards of $100K.
The "bed of nails" fixtures are used with Automatic Test Equipment (ATE), which is usually computer driven, and provides the necessary power and signals to the circuit, measure the circuit's response to the applied stimulus, and compare the response to specific limits. ATE systems require all the necessary computer-driven (usually GPIB interface) test equipment and a test program (software) that was written specifically for the equipment being tested. It's not cheap (up to several million $$$$$). On the flip side, ATE systems don't usually require an experienced tech to repair a circuit. The ATE system tests the circuit, and if it fails a test, the ATE tells the operator which components to replace. The operator replaces the suspect components and retests the circuit to verify the repair. ATE systems are also used to verify unpopulated circuit boards, especially useful when they have multiple layers. Manual verification of a PCB having hundreds of individual traces would be extremely time-consuming and expensive.
No, these are not the only methods of troubleshooting circuits. If you have the necessary signal generation equipment (analog and/or digital) and response measurement equipment (scopes, meters, analyzers, etc.), you can manually troubleshoot.even the most complex equipment. The more complex the equipment, the more knowledge and expertise you will need.
There's really no substitute for a good knowledge of electronic theory and the ability to use it when analyzing a misbehaving circuit.
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Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in
the address)
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