HP HP-Bench-Briefs-1982-01-02 free download

File name HP-Bench-Briefs-1982-01-02.pdf

u a E N FROM HEWLETT-PACKARD JANUARY-FEBRUARY 1982 Functional Analyzing B y Jim Bechtold, Editor Introduction Functional analyzing usually pro- vides the most direct and efficient means of isolating a problem in an electronic instrument. As another term for logical troubleshooting, functional analyzing is more appro- priate and descriptive of the process used in everyday bench service. Func- tional analyzing is antithetic to shot- gun troubleshooting because func- tional analyzing involves analyzing Figure 1. Mike Keenan, HP Technical Specialist, substitutes part of a good DVM into a faulty the unit in logical, sequential steps in unit as a form of haif-splitting. order to isolate the defective circuit, rather than jumping around replac- showed how the step-by-step proce- was turned on, all annunciator lights ing components at random until the dure could be used to isolate a problem were illuminated and the display problem goes away. in the electrical charging system of an remained blank. The DVM would not automobile - a rather simple exam- respond to any switch settings. Before A bonus to this logical, sequential ple. This article shows how these Mike applied AC power, he removed diagnosis is that when you do discover same basic procedures are applied in the covers and looked and smelled for the cause of the problem, you acquire troubleshooting a complex electronic evidence of broken components or a kernel of knowledge that is added to instrument - a microprocessor con- heat. Everything seemed OK so Mike your bank of experiences. Then, if a trolled 6%-digit integrating digital connected the DVM power cord and similar problem occursagain, you can voltmeter (see Figure 1). switched the unit on - in fact, he draw upon your bank of past experi- switched it on and off several times. ences and mentally bracket the prob- To document the procedure, I sat at The DVM repeatedly locked up at lem area. Troubleshooting a n in- the bench with one of Hewlett- turn-on just as the customer had indi- strument by the shotgun method will Packard's repair center technicians, cated. Milking the front panel re- generally effect a repair, but you will Technical Speciali