Electronics > Repair

Fluke 8840A Faulty CPU

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giosif:
Thanks for your input!
I too suspect some timing type of problem, but I don't really have proof for it.

Also, you mention v4.0 for 8840A. Did you really mean v4.0?
I am asking since the highest version I've ever seen/heard of for the 8840A is v2.5.
Could you share that FW v4.0 with us, please?

Thanks!

Kjo:
@giosif
The only specs on the UB8840M are in mostly non-English. But to my recollection when I designed the clone the UB8840M only addresses 4K on the buffered external ROM bus. But there are a few things about the Fluke 884x firmware that I have never quite understood.
In most meters there are 2 4K ROMs. The low 4K is embedded in the MCU and the hi 4K is external. The external ROM is enabled by P22 & DM from the MCU. So the low 4K in the MCU has to use port mapping signals to read the hi 4K. But there are a few late 90’s meters that have OTP or windowed Z86E21 8K EPROM MCUs where there is no device in the U222 socket. I have 3 such meters. Two of the 3 had the Z86E21 code protect bit set. Ha Ha Ha the third I could read out the firmware as an 8K block. I split this ROM in to 2 ROMs at the 4K boundary. After writing the 2-4K images into 2732A EPROMs, I put the low in a Z8613 piggyback and the hi into U222. The 8840A booted and passed all tests exactly as the original Z86E21 did.
So there is something about the operation of the Z86E21 I am unclear on. The 4.0 firmware clearly works as 2 ROMs but also as contiguous 8K memory. These Z86E21 are STM parts, and while I can read out the ROM, my programmer will not program them. So I have to send them out to get programmed.

Back to your request. Rather than dumping the ROMs here, I put all the ROM data for all the meters I have collected on my website. Anyone can grab what ROMs are there for what ever use. Not all ROM versions have code for the U202 MCU. And remember that all 3 meters have unique, non-interchangeable firmware.
HTTPS://www.Hollywoodcontrols.com/phpFluke/HC8840A_roms.php

If anyone has ROM data that I don’t have please let me know.

Kjo KO3Y

giosif:
Thank you, Sir!

I was able to download the v4.0 firmware.
I burned the 2 x 4K files and tried them with the UB8840M adapter and the meter works fine now.  :-+
Strange that the exact same adapter did not work with v2.3 of the firmware, but it works with v4.0.
In any case I am happy.  :)

On a side note, I happen to have a Z86E21, which I burned with the 1 x 8K version of the v4.0 firmware and I confirm this one works as well (I didn't install an EPROM IC at U222, as that wouldn't be needed anymore).

Kjo:
@giosif
Glad to worked 4 you.  I have no idea what Fluke changed in the 8840A V4.0 fw.
But it works fine. What did u use to program the Z86E21 device?
Kjo - KO3Y

giosif:
I used a less known programmer, Micromaster LV, made by a company called Ice Technology.

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