Agilent U1252A measuring consistency recovery FIX with ultrasonic cleaner bath

[Kiriakos GR]

Agilent U1252A this is a DMM that I do not own.
Even so from time to time I do read complains, that a good quality HH DMM may appear having issues with:

Resistor measurements not stable, or not a warranted repeatability.

Test leads warning Alarm for current inputs, this activates all by itself.

Functions rotary switch (aka range switch back at 80s), not stable or good contact with the inner PCB.


Gentlemen, never seen such an issue at my own HH DMM, I do well take care of them when using them indoor and outdoor.
But for all of you out there, there is a serving tip.

The use of ultrasonic cleaner bath with a portion of isopropyl alcohol, this saved the day of many people.

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Yes, it is required with caution to take the DMM apart, disconnect Liquid crystal screen, and to leave the PCB alone this having a cleaning cycle.
In case that the DMM has secondary PCB for it banana inputs?  This should get in the bath too.
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Back in time FLUKE Corporation, it was delivering special instruction as PCB disinfection process.
For their DMM with thru hole components.

At our times, all DMM using surface mount components, all components placed too close to its other.
Electrical isolation this is now more easy to be lost.

Field technicians whom working at industrial environments, they are well aware that particles in the atmosphere, they might be from metal.
Especially Plasma cutter machines, these creating a cloud of metallic particles, and this cloud it can cripple all sort of electronics.
(Industrial windows PC, CD DVD drive, ATX PSU, and many more. )
Electric welders, they are an another source this creating a cloud of metallic particles, especially when they are many in action. 
 

[Kiriakos GR]

I feel the obligation to share a warning note, mostly because I had never use any ultrasonic cleaner in my life.

The ultrasonic cleaner, this is a generic device regarding it theory of operation.
This technology comes for 90s,  just check at eBay for used items, and you will discover older designs appearance and features.

Chinese advertising this mention PCB cleaning, as an added sales point.
But they are not out there, actual instructions of how to setup the ultrasonic cleaner appropriately, for this application.

Newer designed ultrasonic cleaner, they have the ability to heat the water and or any cleaning liquid solution.
Some have Full-Wave and Half-Wave output adjustment.
All these belong at the sphere of tweaking, for best results at specific application.

Since the moment, that there is not out there any instructions that you can trust.
I would advice to follow first the old times method, as is documented by FLUKE.

At modern DMM they are soldered over the PCB, sensitive to vibration resistor networks, inductors, and other sensitive components.
What I am trying to say is, that there not available as single medicine for all health problems.

My suggestion to hobbyist, you should request professional help, from a freelancer professional in electronics repairs, so him to inspect your multimeter.