Conference kernel::csguk_systems

169.0. "QTIP: RW5xx SCSI Termination power Tech Tip" by KERNEL::PETTET (Norm Pettet CSC Basingstoke) Tue Feb 22 1994 12:23

From:	HOTSPR::BROWNLIE "Broken product specialist....833-3932  22-Feb-1994 1225" 22-FEB-1994 12:20:58.23
To:	@[brownlie]trf.dis
CC:	BROWNLIE
Subj:	QTIP: RW5xx SCSI Termination power Tech Tip


       +---------------+
       |     QTIP      |   FOR USE BY DIGITAL PERSONNEL ONLY
       +---------------+



From:	COMICS::LOANE "UK Customer Services Support (833-3309)  18-Feb-1994 
1022" 18-FEB-1994 10:34:53.02
To:	@[.DIS]STORAGE.DIS
CC:	
Subj:	RW5xx Termination power Tech Tip



          Controlling SCSI termination power on Digital RW500-series
          autochangers:

	
          Problem Symptom A: Host no longer recognizes jukebox or drives,
          it appears that they are offline.

          Diagnosis A: The jukebox is triple or mega terminated, caused
          by the drives being terminated or extra termination from the
          SCSI repeater pca or extra termination from directly connecting
          to a box such as the BA350 which is connected to the HOST.

          Solution A: Check each jukebox drive, for three yellow termination
          resistor packs.  These packs are located under the SCSI cable.
          Remove all three if they are found(should only see this situation
          in the case of a drive upgrade ie. 650MB to 1.3Gbyte drive). Then
          replace the SCSI repeater board.

          Check SCSI repeater pca, near the edge where the external SCSI
          cable connects.  Should see three resistor packs in the parking
          lot. If they are not in the parking lot, replace the SCSI repeater
          board.

          Check cabling to the host. If connected thru a BA350 box, disconnect
          SCSI cable and reconnect directly to the host.  BA350 box has its
          own termination, which will induce triple termination and blow
          the SCSI repeater module.

          If any of the above cases are true, must replace the SCSI repeater
          module.  If none of the above cases are true, then check the fuses
          on the SCSI repeater module.  If any are blown the module needs to
          be replaced.


          Problem Symptom B: Receiving term power error messages from the host.
                       
          Diagnosis B:  SCSI repeater module was shipped with termination
          disabled.
          
          Solution B: Enable termination power.  See details below.


GENERAL BACKGROUND
------------------

          Digital Equipment Corporation RW510, RW514, RW516, RW530, RW534
          and RW536 autochangers contain a SCSI repeater module which
          distributes the SCSI signals throughout the autochanger.  This
          SCSI repeater module is capable of providing termination power
          to the SCSI bus internal to the autochanger/drives and to the 
          SCSI  bus external to the autochanger. Digital RW504 and RW524 
          systems do not contain a SCSI repeater module and provide 
          external SCSI termination power on the controller module.  All 
          Digital Equipment Corporation RW500-series autochangers enable
          termination power on both internal and external SCSI bus by
          default.


TERM POWER ENABLE PROCEDURE
---------------------------

          SCSI termination power may be disabled or enabled by placement
          of jumpers on the SCSI repeater module (or on the controller
          module in the case of the RW504 and RW524).  The SCSI repeater
          module is located under an access panel at the rear of the
          RW510, RW514, RW516, RW530, RW534, and RW536 autochangers.  The
          Controller module is located along the side of the RW504 and
          RW524 near the front of the cabinet.  To gain access to the
          appropriate module, read the section on Removal and Replacement
          in the Service Manual for your model of autochanger.

          The SCSI repeater module is fastened to the rear access panel 
          on RW515, RW516, RW534 and RW536 autochangers.  There is one 
          jumper for the internal SCSI bus termination power and a separate 
          jumper for the external SCSI bus termination power.  There should be
          three termination resistor assemblies adjacent to the SCSI cable
          connectors on the SCSI repeater module.

          There will be a legend on the SCSI repeater module indicating
          "TERMPWR" near one set of jumper pins adjacent each SCSI cable
          connector.  When the jumper is in the position nearest the
          legend, the termination power is applied to the nearby cable.
          When the jumper is connected to the other set of pins, SCSI
          termination power is disabled on that segment of the bus.  Small
          fuses (rectangular white blocks) are near the connectors.  The
          fuses apply protection between the SCSI termination power supply
          and the SCSI bus itself. RW504 and RW530 systems have termination 
          power for external SCSI busses only.     

          Once the jumpers are in proper position (enabling or disabling
          SCSI termination power), reassemble the rear panel, re-connect
          cables and apply power to the autochanger using the directions
          found in the Service Manual.