MJ-X Troubleshooting Guide AED-000025-04
Siemens T&D
LLC
2 version: 5 January 1998
1. Troubleshooting the MJ-X
This document outlines a process for preliminary troubleshooting of the MJ-X. The major objectives are:
1. determine if the fault resides at the MJ-X
2. check for improper jumper arrangements or other easily correctable conditions
3. check for field/customer repairable fault (e.g., bad fuse or Neutralite bulb)
4. If necessary, document problem details for factory repairs.
2. Basic Approach
For efficient troubleshooting, the following basic approach is recommended.
1. Verify configuration (hardware & software.)
2. Make sure the control panel hardware & software support the feature(s) you want to use.
3. (Consult MJ-X software revision documents.)
4. Substitute a known good panel. Check if it duplicates the symptoms. If so, the problem is more
likely with the system or wiring rather than with the MJ-X. (This is not always the case.)
5. Use this troubleshooting guide to isolate and fix the problem if possible. If field fix not feasible,
document problem in detail for factory repair.
The following assumes you are familiar with both the MJ-X operation and the MJ Suitcase Simulator. For
further information on these topics, refer to the appropriate user manuals. You also need to be familiar
with safety procedures for electrical and electronic equipment.
3. Test Equipment
Siemens recommends the following test equipment: 1) MJ suitcase simulator, 2) True RMS Volt/Amp
meter, and 3) PC running MJXplorer.
If using the MJ suitcase tester, connect to the PDS ("jack plug") cable. [As an alternative, provide a
nominal 120VAC at the external power banana plugs and a 0-200 mA current source at the PDS C2/E1.]
Unless otherwise noted, tests are performed with U2 and P2 at 120 VAC. [E must be connected to E1 at
the PDS if the suitcase tester is used for these tests.] {Caution: If using external power, be aware that
several of the PDS connections are hot.}
For tap motor direction sensing with the MJ-X, the “J” and “K” jack plug signals must have a minimal
resistive load. If you’re not using the MJ simulator, connect load resistors (2.2K 10W) from J to E and K
to E at the PDS (jack plug).
3.1. MJ Simulator Overview
The MJ suitcase simulator provides the following test capability: variable voltage sources (for U2 and P2),
variable current source (for C2), toggle switch for Straight/Inverted regulator simulation, toggle switch for
Inverted Source Side Potential Transformer (SSPT), Neutralite test button, Operations Counter test button,
Drag Hands Reset indicator, “J” (Raise) indicator, and “K” (Lower) indicator. With the MJ suitcase
simulator, you can simulate forward & reverse power flow, and leading/lagging power factor.
When pressed, the Neutralite and Operations Counter buttons ground (short to “E”) the jack plug signal
U12 and U10, respectively. Otherwise, these signals are open. The Drag Hands Reset Indicator lights
when the Drag Hands Reset signal (jack plug U11) has a nominal 120VAC. The “J” indicator lights
when the jack plug “J” signal has a nominal 120VAC. The “K” indicator lights when the jack plug “K”
signal has a nominal 120VAC.
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