EEVblog 1564 - Agilent/Keysight U1273AX Multimeter Repair

[EEVblog]

A very interesting repair of an Agilent/Keysight U1273AX OLED display multimeter. It had two distinct unrelated faults.

Available for auction from 99cents: https://www.ebay.com.au/itm/225767769508
Ian Scott Johnston on The Amp Hour: https://theamphour.com/643-calibration-repair-with-ian-johnston/
Thin film ceramic hybrid resistor networks:

[sonic]

The screen of my U1253B got very dim after 9 years of light use. After trying the german Keysight support to no avail I got a replacement from https://parcelup.com/shop/item.php?id=591402268582#4133487996875
At least their U1253B version doesn't have the mirrored-after-menu issue.

[SiliconWizard]

Those small OLED displays look cute but they aren't very reliable. Also, try seeing anything in direct sunlight.

[lty1993]

The last time I contacted Keysight US about the replacement of the OLED, they informed me that if the product is no longer under warranty, the only available option is to purchase a new meter.

[Shonky]

Seems like the replacement board is not very good and is not initialising the OLED controller properly.  i.e. OLED controller resets, but STM32 on the driver board doesn't re-initialise it and you end up in the reversed mode? Pretty poor and you'd think it would have shown this multiple times whilst developing it.

[Macao2Blue]

Hello, I hope I am not too late, I am not a subscriver of your youtube channel.
This was my dads last multimer and the only one I had so far that connected to the computer, I tryed to upgrade it some years ago and it failed, I can not do anything with it , was too expensive to pay to fix and I don't known how to fix it. I asked my mum and she can send it for free to you, you can use the front and back covers so that the new onwer can have a really nice one, also working display (I think).
Despite my current multimeter having no computer connection it does the job so I am not looking for a multimeter at the moment, I am saving for an digital oscilloscope and in 2 years I should have access to nice stuff at the university.
I would really like to give these parts some usefullness so I hope I can send them to you, can you send me an email?

[thm_w]

Hello, I hope I am not too late, I am not a subscriver of your youtube channel.
This was my dads last multimer and the only one I had so far that connected to the computer, I tryed to upgrade it some years ago and it failed, I can not do anything with it , was too expensive to pay to fix and I don't known how to fix it. I asked my mum and she can send it for free to you, you can use the front and back covers so that the new onwer can have a really nice one, also working display (I think).
Despite my current multimeter having no computer connection it does the job so I am not looking for a multimeter at the moment, I am saving for an digital oscilloscope and in 2 years I should have access to nice stuff at the university.
I would really like to give these parts some usefullness so I hope I can send them to you, can you send me an email?

Why not buy the display yourself and fix it, then sell it? As you can see in the video its not that difficult.
Or just sell it on ebay as powers up dead display, for parts.

[Macao2Blue]

Why not buy the display yourself and fix it

The multimeter does not work because of me upgrading it with the computer and failed. It powers up displays the brand and nothing else happens. If the issue was the display I would have fixed it!

just sell it on ebay

Ebay only allows users above 18years old.

Front and back cover are almost as new and no battery leaked, would be happy to find some usage for them

[David Hess]

Voltage offset which changes with the meter range can mean high leakage from the input buffer and shunt protection circuits into the series resistor used for overload protection and the input dividers.  The reading changes when different input dividers are selected because their parallel resistance changes.

Automatic ranging meters usually have a manual ranging mode however often the manual ranging mode does *not* control which input divider is active and instead automatic ranging is still used to do that which makes diagnosing leakage difficult.

[pts]

What about plastic not handling Battery acid?

What about leakage from battery compartment reaching the PCB board in the first place?

with current construction It seems unavoidable that leakage from battery compartment can damage the PCB.
Should be avoidable with proper design.

How common is these kind of problems

[Kleinstein]

It is a bit strange to use a kind of plastics that is not resistant to the liquid leaking from the typical batteries. Leaking batteries are a really common thing - among the main causes a broken meter.
It is however rare that products are designed with a water proof battery compartment and maybe an absorber to catch leaking batteries.

[onesystem]

With help of eevblog members from microcontrollers board, we were able to dissect the firmware and patch it to work with current OLED screens (with driver SSD1309).

Here is the firmware dissection process:
https://www.eevblog.com/forum/microcontrollers/8-bit-78k0-d78f0547-help-with-firmware-modification

Here is the procedure for screen replacement using patched firmware:
https://www.eevblog.com/forum/repair/agilent-u1273ax-dead-display/msg5282710/#msg5282710

This way meter works properly no matter if you are in setup menu, regular measurements or if you turn it off and on too quickly.

Also cost is way less since you are only paying for OLED screen with driver SSD1309 only and nothing else.