I’ve got some great luck with recent acquisition of RoHS black Keysight 3458A. Fastest 3458A repair ever was also documented on my YouTube video here.

Per xDevs.com’s definition in this work in progress article this DMM belongs to latest Gen6 generation of hardware so it’s good to have a set of photographs about internal parts and PCB circuits.

Originally released updated RoHS 3458A from Keysight had few of it’s new boards designed by wekomm engineering GmbH around year 2018-2019. This was what xDevs calls a Gen 5 variant. It’s kind of funny that wekomm main website used new RoHS 3458A’s A1 board photograph on a light-table as artistic marketing background. :)

Later Keysight actually made their own copies of the boards for mass production. This is the unit we’ll look at in this article below. Instrument was manufactured in Malaysia and calibrated by factory on 6 January 2022 using Fluke 5730A with 5725A amplifier and reference golden Agilent 3458A MY45032088 DMM. This DMM has no additional options (former 001 option is now included as default in every 3458RoHS unit).

Disclaimer

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All information posted here is hosted just for education purposes and provided AS IS. In no event shall the author, xDevs.com site, or any other 3rd party, including HP/Agilent/Keysight be liable for any special, direct, indirect, or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortuous action, arising out of or in connection with the use or performance of information published here. This guide is not official recommendation or endorsement from manufacturer.

If you willing to contribute or add your experience regarding HP/Agilent/Keysight instruments repairs or provide extra information, you can do so following these simple instructions

Enjoy the photos, all 300 of them. Hopefully this would be helpful insight for all 3458A owners out there.

Teardown of Gen6 Keysight 3458A RoHS, year of manufacture 2021

Mechanically new meter is identical to old units, so let’s dig into it.

Interesting bodges around firmware flash chip.

Transformer has datecode 18 week 2021:

Interesting non-factory looking sticker “4ppm” on A9 LTZ1000A reference module cap. Not that it means much, since nearly all of the LTZ1000A chips capable to hit 4 µV/V/year drift levels just after few years of running without much issue, even with original very high oven temperature. New RoHS 3458A A9 still using same +95 °C oven temperature setpoint for LTZ1000A that makes it worst 8½-digit stability DMM on the market, on paper specifications. In practice, many good aged HP 3458A can even demonstrate stability below 2 µV/V/year which was once sold as special Fluke/HP 3458HFL model until Fluke gobbled up Datron/Wavetek and released 8508A.

Main artifact calibration resistance reference element is good old VPG VHP101T with nominal 40 kΩ.

Keysight also killed off discrete JFET input preamplifier circuitry and just used integrated Texas Instruments OPA140 instead.

Teflon capacitor made out of coil of coax wire is still in place, just like HP guru’s designed it.

New 3458A has now flat ferrite choke on ribbon cable going to the front panel PCBA.

Looks on A3 and A2 with inner shields removed.

Summary and conclusion

Overall, it’s great to see that Keysight still continue to carry the torch of 3458A 8½-digit DMM in production, almost 40 years since it’s original design time. Hopefully they are still working on a new “3459A” DMM that can bring us more performance and better capability in some future.

Discussion is very welcome thru comment section or at our own IRC chat server: xdevs.com (port 4808, channel: #xDevs.com). Web-interface for access mirrored on this page. If you have information and performance reports of various standards not mentioned or listed in this article, feel free to provide them and we will showcase them on site.

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