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.