27052 Modifying the ipg_stage File to Emulate E-Stop Circuitry.

Modifying the ipg_stage File to Emulate E-Stop or Door Switch Circuitry. See Long Description. Modifying ipg_stage file to emulate E-Stop or Door Switch when Compact PDU 24V E-STOP voltage fails creates a safety issue and must not be done - FPR 13012747 Modify mgd_stage for Excite Ovation. Effectivity: All Signa MR Systems equipped with a Compact PDU with model numbers 46-317099P1 thru P4, P8 thru P16, & P20 thru P22. This does not apply to other PDU types. Problem Description: Transformer T5 inside the Compact PDU produces a voltage that is rectified to 24VDC by the circuitry on the SCR Sense Board inside the Compact PDU. This 24VDC is used for both the external E-Stop circuit loop (see the appropriate Block Diagrams Manual for a map of the path of this loop around the system) and, when an E-Stop event happens, for tripping the Compact PDU circuit breakers through each breaker’s shunt. When an E-Stop event happens (someone presses one of the E-Stop buttons somewhere in the E-Stop chain) in a Compact PDU the 24VDC E-Stop voltage is at that instant applied to the RF, Gradient, and Penetration Cabinet circuit breaker shunts (CB6, CB7, CB8, CB13, CB17, and CB18). This causes the circuit breakers to trip open and AC power is removed from cabinets connected to these circuits. It is important to understand that this voltage is only applied to the circuit breaker shunts when an E-Stop event happens. If transformer T5 fails open during operation then stored voltage is applied to the circuit breaker shunts and the affected breakers will trip open. The MR system will detect the loss of the 24VDC and will generate a fault to keep the system from scanning. A message advising that the PDU E-Stop 24V has been lost will also be logged in the MR system error log and posted in the Message Window for the customer to see. If the 24VDC is lost, it will still be possible to reset the tripped circuit breakers and re-apply power to the RF, Gradient, and other affected cabinets. The system, however, will not permit scanning since the system can detect the 24VDC E-Stop signal is missing. If an RSE or FE then modifies the ipg_stage file to ignore the loss of the 24VDC and permit scanning, the system will afterwards have absolutely no E-Stop functionality. Once this change in ipg_stage has been made, systems equipped with 8.X or 9.X software will post a message in the error log and a persistent message in the Message Window advising that PDU monitoring has been emulated. If the problem isn't quickly repaired and the change removed from the ipg_stage file, however, customers may become accustomed to seeing the message and forget what it is trying to tell them. Systems with 5.X or an earlier release of software will not post any advisements in the message window indicating that the ipg_stage has been modified. The customer would be unaware that any changes were made and that the E-Stop circuit is inoperative. This wouldn't be discovered until the next time the E-Stop functionality is needed. This situation can only occur on systems equipped with a Compact PDU. SMILe - June 3, 2004