siudi 7b malfunction

[tojinzgz]

Hi,
i have a suite2fc (siudi7b v1.2) and following a derivation on the dmx line, we have a transmission troubles.
only can use a 20 cm long dmx wire. if i put more dmx wire, signal have a lot of errors. i changed the dmx chip because the another was damaged by the derivation. i inserted a new one chip (SIPEX SP485EC)

SOLUTION?
thanks