Why is the port 2 of the PCD3.Mxxx no longer working?
On the first PCD3 hardware series (up to HW version D) the port 2 (RS 485) was the most frequent cause for repair. The reason was that no active protection (supressor diodes) could be present due to the relatively higher frequency (115KB). Some too big potentiel differencies on the port could damaged it!
A HW modification was introduced in February 2008: a new IC driver containing supressor diodes is now assembled on all the PCD3 since HW D Modification 3. This modification increases the robustness of this port (note that the specifications given in the manual were already fulfilled with previous hardware version and has been furher improved by this modification).
All PCD3 which are send for repair are updated to this HW version (D mod. 3). Of course the next HW version (E, etc..) are already equipped with this modification!
The experience shows that despite of this improvement a defective RS485 onboard port 2 is frequently the cause for repairs of the PCD3 systems. In order to avoid a damaged port 2 (on an installation where the common ground potential and an undisturbed signal can not be guaranteed) it is strongly recommended to apply a galvanical separation externally.
PCD3 / Mxxx
Last update: 31.05.2015 02:23
First release: 17.09.2008 11:16