Information Notice No. 92-31: Electrical Connection Problem in Johnson Yokogawa Corporation YS-80 Programmable Indicating Controllers

                                UNITED STATES
                          WASHINGTON, D.C.  20555 

                               April 27, 1992

                               YOKOGAWA CORPORATION YS-80 PROGRAMMABLE 
                               INDICATING CONTROLLERS


All holders of operating licenses or construction permits for nuclear power 


The U.S. Nuclear Regulatory Commission (NRC) is issuing this information 
notice to inform addressees of a potential electrical connection problem in 
the read only memory (ROM) chip sockets of Johnson Yokogawa Corporation 
(JYC) YS-80 programmable indicating controllers (controllers).  It is 
expected that recipients will review the information for applicability to 
their facilities and consider actions, as appropriate.  However, no specific 
action or written response is required.

Description of Circumstances

In July 1991, Yokogawa Electric Corporation (YEC), parent company of JYC, 
issued engineering service note (ESN) 102E, "Troubleshooting of User ROM 
Socket for YS-80 Programmable Instruments."  In ESN-102E, YEC stated that 
YS-80 controller models SLPC*E, SLMC*E, SCMS*E, and SPLR*B had ROM sockets 
that did not properly engage ROM pins when the ROM was installed in the 

YEC stated that the problem was caused by the material of the ROM socket 
wear plate blades.  This material did not exhibit sufficient spring pressure 
to adequately engage the ROM pins when the ROM was mounted in the socket, 
which could cause an intermittent or inadequate electrical connection when 
the ROM was mounted and locked in its socket.  JYC has distributed a letter 
to its sales representatives to inform them of the concern.

The YEC design staff in Nakacho, Musashino-Shi, Tokyo, Japan, discovered 
this problem while redesigning and improving the YS-80 controller.  YEC 
determined that any of its YS-80 controllers could exhibit this problem.  In 
ESN-102E, YEC listed the following symptoms of the problem: (1) the fail 
lamp illuminates and the controller displays check codes "10," "00," and 
"04" and (2) the digital input is not being sent to the controller, but the 
instrument is operating as if receiving input.  YEC stated that the symptoms 
of the problem could differ depending on the program in the ROM.


                                                            IN 92-31 
                                                            April 27, 1992 
                                                            Page 2 of 2 


The NRC staff was informed of this problem in a December 23, 1991, letter 
from Spectrum Technologies USA, Incorporated (Spectrum), and a January 7, 
1992, letter from Nutherm International, Incorporated (Nutherm).  Nutherm 
supplied a total of 22 YS-80 controllers (models SLPC-271*E and SLPC-281*E) 
to the Commonwealth Edison Company, and Spectrum supplied 26 YS-80 
controllers (model SLPC-281*E) to the Tennessee Valley Authority.  Both 
vendors informed the affected licensees of the problem. 

JYC recommended that users not make any field changes to the ROM socket 
because this action could damage the interfacing printed circuit board.  
Instead, JYC suggests that applicable NRC licensees contact Mr. John Jerman, 
Manager of JYC's Technical Assistance Center, at (404) 254-0400, 
extension 137, for further assistance and information.

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
the JYC staff member listed above, one of the technical contacts listed 
below, or the appropriate Office of Nuclear Reactor Regulation (NRR) project 

                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical contacts:  Randolph N. Moist, NRR
                     (301) 504-2981

                     Joseph J. Petrosino, NRR
                     (301) 504-2979

Attachment:  List of Recently Issued NRC Information Notices

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