On some installations, it is possible to have false ground faults triggered on Titan channels driven from IED6002 line driver cards.  The reason this is only a problem on some installations relates to component tolerances and actual loads attached to the 6002 outputs (e.g., connecting to unbalanced audio line).  Below is the background on why this happens, which can be skipped if desired.  The second section is how to correct for this problem by adjusting values using the ViewProp tool.

Background on What Happens

The process of monitoring for ground faults involves putting a small DC voltage on the speaker line (nominally 5 V) and detecting when this voltage goes below 3 V.

1. With an amplifier in a slot, the voltage with no ground fault is around 5 V.
2. The 6002's line driver circuits have some impedance to ground, causing the internal voltage normally to drop to about 3.6 V -- only 0.6 Volts above the fault threshold.
3. It's possible that due to manufacturing variances or installation matters, the normal voltage on some Titan frame(s) are closer to or just below 3.0 V.

Correcting for the Problem

The ground fault threshold can be adjusted via ViewProp.  If the installer is unfamiliar with this tool, it may be best to let an IED technician handle this via suitable remote access mechanism.  Part of this investigation should be to determine whether the ground fault may, in fact, be real. 

There are two LVIO cards in the Titan frame accessible by device handles 32757 and 32758.  These cards are for the first 8 and the last 8 speaker lines, respectively. One should access only the FIRST LVIO Contact Group Object in each device.  The first object manages the ground faults, the other objects in each device are for amp good signals, temperature faults, fan faults, etc.

If accesses these cards via VewProp and opens the first LVIO Contact Group Object, one will see properties such as those shown in the attached screenshot. Properties 2p11 – 2p18 are the current DC voltage readings.  For normal amplifiers, one should see values just above 5V as in the screenshot. 

The properties 2p21 – 2p28 are the current logic state.  In the example screenshot, these are 4, which means the voltage is above Logic Threshold 4, but below logic threshold 5 (2p34 and 2p35).  A ground fault is declared for a current logic state below 3 (nominally 3V).  

If one is seeing “normal” readings for lines, i.e., with readings around the 3V threshold, then one can fix the fault by lowering Logic Threshold 3 (2p33).  For example, if you are seeing 2.8V, then maybe you change  2p33 to 2.0V or 2.2V. 

After making these changes, exit the properties window and press the Make Perm to lock these changes into non-volatile memory.

But, if one sees really low voltages, then STOP and investigate the possibility of a real ground fault.  For example, if one side of the 6002 line driver may be going to ground because it is driving an Unbalanced input.  The two options for fixing this are: 

1. Turn off ground fault detection (e.g., lower all of the thresholds to 0V)
2. Put an isolation transformer at the FAR END of the connection to the other equipment.  That way, we can still monitor the line between the Titan frame and the isolation transformer for ground faults – assuming that is what is desired.