Electronics > Repair

Keithley 2015 odd power-up problem

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AndyC_772:
Hi all,

I bought a Keithley 2015THD a couple of weeks ago. It seemed to be working well.

Yesterday I switched it on, but it hung during the boot process. All the display segments towards the left and right sides of the screen were lit, the ones near the centre were off, and after a few seconds I heard a relay clicking on and off quite rapidly (a few Hz). I power cycled the unit and it's not misbehaved again.

I'd previously opened it up (shortly after it arrived) and checked inside with a thermal camera, and there was no evidence of anything getting unusually hot - apart from a couple of ICs near the voltage reference, but they're less hot in the 2015 than the equivalent parts in my older 2000.

My initial reaction was it's likely to be dead caps in the power supply, but once they're dead I'd expect them to stay that way. I'd also have expected them to be getting noticeably warm when I checked the unit earlier.

I guess there's not a lot I can do until the symptoms recur - unless there are any known weak points that result in intermittent failure to boot...?

grumpydoc:
Part dead caps have certainly caused me intermittent problems in Tektronix psu's. It sounds like the microprocessor didn't reset properly which could easily be a 5V (or whatever) rail ripple issue.

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