HP 3468A in continual reset/init?

[MarkL]

Bummer on the checksum and multiple bit errors.  But a valiant effort!

Here's an idea.  If the bits are marginal, it may be possible to vary Vcc to see if the MK36000 will read correctly.  You could take it out of circuit so nothing else gets ruined, and maybe try 4.0V to 7.0V (absolute max).  Lookout for the higher voltages coming out of the data lines if you connect it to an Arduino to read it (use series resistors).

I recovered calibration data from a flaky EEPROM in a 2465 scope with this method.


I guess the reason there's no convenient images sitting around is that the ROM has to be unsoldered to read it.  Someone with appropriate soldering skills and a reader has to be willing to do it to their working meter.  (While being careful around the NVRAM and battery.)

There's two versions of the ROM, 1818-1753 and 1818-3123.  Hopefully there's no hardware dependencies tied to a specific version.

[Kjelt]

EXCELLENT idea Kjelt . Perhaps you would like to initiate it?

Done: forum/testgear/hp-3468a-owners-unite-a-storm-is-coming! (can't get the link to work)

[intabits]

... I will carry out a disassembly of the 3478 ROM, believing that I can identify that section of code which must be essentially identical to the 3468....

Did you get anywhere with that?
I've recently scored three 3468A's, and all are in great condition.
But the LCD displays on these (and 3457, 3478) are pretty crap IMHO, and I'm looking into hacking a better display onto them.
Trying to figure out how the display is driven by monitoring the signals to it would be quite a job, but I imagine working from the ROM code might be slightly easier.
Hence my question...