Display's Netplex link is Down again

[Crrispy]

Hello,

I open a new topic because the previous one is tagged as Solved. It was too nice to be true (just removing U16, green batt, and changing the mpu battery). Xmas family reunion, good time to power on the Denver Duck, and the infamous error is there again, straight at startup on the display. Any idea on the next step?

Thanks.

[Crrispy]

So, I've removed the mpu, sprayed in a ton of contact cleaner on the connectors, did the same on the vfd connectors, and removed the bill validator to test.
After waiting for it to dry and powering on, the netplex error is gone but now I have 2 other errors at the end of boot: Door open M, and bill validator comm failure, even after putting it back in place. I already had issues with the door open M message in the past.

Seems I need to get rid of both. Is this drawing OK to bypass the door optics? I found it in another post.
How can I completely get rid of the bill validator?

At least I'm pretty sure I don't have a PSU issue.

Thanks.

[Crrispy]

So, I've found and done this bypass for the door optics (same as above), it seems to work. The bill validator comm failure has disappeared together with the Door M error, nice, but I'm still interested if there is a way to disable it completely, since it is of course useless for home use.

Thanks.

[Stayouttadabunker]

Yeah...that's an old drawing I made...lol
I can't remember the last time I've used actual door optics. 
Try these troubleshooting notes below...>>>

How to diagnose a netplex link down error.

First disconnect all netplex drvices except the vfd. 
This includes the bill acceptor, printer, some progressive displays, some top box bonus devices.
Now that those are disconnected check the following.

Is your error solid or blinking.
Blinking
     Do you have a 50x or 1270 mpu?
     1270
          Remove the varta and u16.
      50x
          Mpu fault.
Solid
     Do you get no disp on your credit display
     No
          The mpu is not booting check the mpu for signs of faults or problems with the chips.
     Yes
          Check voltage at the vfd on the 2 pin connector
          Check the data cable for any signs of damage especially where the door closes.
          Mpu is faulty or damaged check for bent pins.

[Crrispy]

Thanks, I hope it won't happen again, but never sure with this machine  Since I solved it with KF contact on the mpu and VFD connectors, it was probably "only" this. I hope so.