Problem- R2E4 debugging

[arsenix]

I have been chasing a communications problem on my R2E4 Series II CNC for quite a while and I am pretty much at the end of my rope. Hopefully someone on here might have some new ideas.

I have localized the fault fairly well at this point but I still can't figure out why it is behaving like it is. Essentially, the UARTs on the BSP2 PCB are not putting out anything. Consequently, I get an SFP communications fault (SFP link dead) as soon as the machine boots. I know the issue is erratic because for a while the SFP communications was working, but then I would get a communications fault with the FDMC PCB.(also because the UART was not transmitting)

I have examined the signals going to the UART using a logic analyzer, and it all "seems" to be fine. I have reflowed every joint on the PCB and replaced most of the interfacing ICs connected to the UARTs to no avail. I have also replaced all the electrolytic caps on the board.

I'm not really sure what tends to go bad with these old boards. It all basically seems to be working... but clearly there is some obscure issue here that evades me. This machine was working 100% before I last moved it. If anyone has any tips I would greatly appreciate it.


James

[machintek]

Check the back of the logic card rack. It folds down. Check logic supply to the boards.
clean all edge connections with a soft eraser.

George