Electronics > Metrology

Fluke 5440A repair

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MegaVolt:
I received a Fluke 5440A in excellent condition with a small error. I thought it would be easy. But I checked everything I could and I don't see a problem: (I will accept any hints :)

This is what I see. When turned on, all the dots on the screen light up except for one position where the "?" This is problem?

Then I see an inscription (DV instead of DC)
5440A DV CALIBRATOR
FRONT PANEL RUNNING

And after the error "FRONT COMMUNIC FAULT"

In the service manual, this is error 64. Loss of communication between A2 and A16. But I switched the device to test mode and with the oscilloscope I see an exchange between these two boards in both directions. Signals are similar to RS232. This means that the UART is working, the processors are working, the communication line and buffers are working. I checked the frequencies they are normal.

What else can you check ??

Firmware except MC68701 I could not read it.

picburner:
The first thing to check is if all the voltages are right and if the ripple of each is within the tolerances shown in the service manual.
A strong ripple on 5VDC could disturb the communications between the main cpu and the front panel as well as create other anomalies.
I have a 5440B which differs in the display (VFD vs LCD) and other little things.

MegaVolt:

--- Quote from: picburner on July 06, 2021, 02:28:35 pm ---The first thing to check is if all the voltages
--- End quote ---

Thanks for your participation.

I have checked the voltages related to the processor boards. Everything is fine. The connection is made by differential signals of 5V swing each. This is a very reliable communication channel :))

But I didn't check the rest of the voltages. Perhaps it makes sense to do everything.

I thought that someone has information on how the ping is done. Or perhaps it has waveforms.

TiN:
Check for life on main processorboard, check reset lines, check XO outputs, check if firmware chips on all digitaly boards is good or not.  :)

MegaVolt:

--- Quote from: TiN on July 06, 2021, 02:59:28 pm ---Check for life on main processorboard, check reset lines, check XO outputs, check if firmware chips on all digitaly boards is good or not.  :)

--- End quote ---
Thank you Ilya for your participation :)

1. The files that I posted are read from the current boards. Unfortunately, I cannot find out how much the correct firmware is in them.
2. Processors work and send information via UART. This means that some of the firmware, reset, and generator are working.

I see that the boards are working, displaying information on the screen and trying to communicate with each other. But something is not going quite the way it should be.

Perhaps the firmware began to be erased and a couple of bits changed their meaning: (((I'm trying to find another firmware to compare. But it's difficult :( I found only one person on the Internet with a similar device :(

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