Author Topic: Crazy HP 3478A multimeter  (Read 1417 times)

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Offline ik5mic

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Crazy HP 3478A multimeter
« on: December 04, 2015, 10:30:14 am »

my working HP 3478A multimeter has become crazy.

At first, last week, it started with U.C. ROM FAILED message at boot, immediately recovered (functional multimeter). After a few minutes of warm-up, and cycling again off-on, the error disappeared.

Now it always displays SELF TEST, U.C. ROM FAILED, and several other messages (e.g.: A.D. LINK FAIL, U.C. RAM FAILED), then after a few seconds the display shows garbage. While the display changes, the input relays switch in a random sequence.

I have checked the power supply lines and ESR for capacitors, but everything is O.K..

Any suggestions for further investigation? Similar experiences?

Thank you and regards.


Offline MarkL

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Re: Crazy HP 3478A multimeter
« Reply #1 on: December 05, 2015, 06:19:49 am »
Have you worked through any of section 7-D on processor troubleshooting in the service manual?

If not, start there.

What equipment do you have available for debugging this?  Scope?  Logic analyzer?

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