Simplex How to Correct Supervision Problem on 4100 Signal Cards

HW97047 How to Correct Supervision Problem on 4100 Signal Cards 4100 4100 4100 4331 4332 3 Input 6 Circuit Class A Signal Card 565 452 4100 4321 4322 3 Input 6 Circuit Class B Signal Card 565 453 4100 4011 4012 2 Circuit Class A Signal Card 565 454 4100 4001 4002 2 Circuit Class B Signal Card 565 455 Resistor R39 Burned on Signal Circuit Card All signal circuits on card lost their supervision voltage Burned Resistor All signal circuits report open circuit trouble Signal circuits report open circuit trouble Open circuit trouble PTC Open No supervisory voltage See attached document Signal Card 10 ohm resistor ten ohm resistor is used to prevent the burning of foil etch on the pc board from taking out the Power supply tap are two common scenarios that cause the resistor to burn Double ground fault this case a 0V is shorted to ground some where in the system While the circuit is being worked on live the Sig Supv line touches ground is now a current path from 24 volts to ground with only the 10 ohm in series Resistor overheats and burns In an audio system the shield is connected to ground at the panel While on the signal circuit live the Sig Supv lead touches either ground or shield of the cable There is now a current path from 24 volts to ground with the 10 ohm resistor in series Resistor overheats and burns the above cases the 3A fuse is on the return side of the circuit Its job is to the Power Supply when the circuit is activated In supervisory if the card circuit is shorted the sense resistor 3.3K limits the current When in and the circuit shorts the fuse limits the current to 3 amps and protects the Supply Resistor R39 10 ohms 25W was found failed open ECO SM940 replaced 10 ohm resistor with a resettable fuse RT7 P N 235 007 Check to see if the in question were older Rev C stock boards The ECO Break in was November 1999 for this change There are date code on the top of these boards The Board Rev level is also identified on the These boards are now Rev D boards