Hi Al,
Would anyone have the firmware from the 8048 uP of the inguard logic board? It's IC A30U13, HP part # 1820-2539.
I picked up a 3456a showing error -3, inguard/outguard isolation failure. The 5V regulator on the inguard power supply had failed. It and all electrolytic caps are replaced now.
The inguard receiver logic was working properly. Reset signals from the outguard processor were making it to the reset pin of U13. U13 power is good. Clock is also fine. There was no response from U13 anywhere. U13 gets an interrupt request from the receiver when a byte is available and is supposed to send out a READ signal on pin 8. Even with pin 8 cut from the board there was no signal after the interrupt, so U13 is gone.
The 8048 can be replaced with the 8748 EPROM version, but I can't find the firmware anywhere. The BAMA archive on the 3456A page does say "The checksum for a good 8048 binary ROM image is 1C936.", but they don't seem to have the file. There have been a few discussions on different boards over the years but nobody seems to have posted this binary.
Some discussion mentioned there had only ever been one version of this firmware, so age of the meter doesn't matter. It seems that the earliest models may have had the 8048 in a socket but most had it soldered in.
Any help finding this binary would be certainly appreciated. (Otherwise, I might just have to buy another broken 3456A to work on.
)
Tim