Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!mips!pacbell.com!att!att!cuuxb!wgs
From: wgs@cuuxb.ATT.COM (~XT6562000~Bill Simeon~C82~rfe~xxxx~)
Newsgroups: u3b.tech,comp.sys.att
Subject: Re: 3B2 SCSI Soft Power fun...
Message-ID: <5728@cuuxb.ATT.COM>
Date: 28 Jun 91 13:42:41 GMT
References: <1991Jun27.021618.664@robohack.UUCP>
Reply-To: wgs@cuuxb.UUCP (William G. Simeon)
Followup-To: u3b.tech
Organization: AT&T Computer Systems, Lisle, IL
Lines: 58

In article <1991Jun27.021618.664@robohack.UUCP> woods@robohack.uucp (Greg A. Woods) writes:
>
>I just went through an episode that gave me a good scare.
>
>I came home this evening to find my DM/135e with its power light out
>and tons of messages spewing out on the console about a bad block 0 on
>that device.  Oh-oh!  I tried an emergency power down, but it
>"failed", so I logged in and tried 'telinit 0' which eventually worked.
>
>When I tried to power back up, only the DCM/4e came on, and not even
>the TM/60S!  After much goofing around and searching through the
>maintenance manual, I finally looked at the SCSI Operations Manual.
>A very short paragraph suggested shutting everything off *and*
>disconnecting all of the power cables, and starting up from scratch.

(Stuff deleted)


Here is an excerpt from a product flash that was issued back in 1988. It
still applies!


The power supplies used in high-end 3B2 Computers (3B2/500,600,700)
and all 3B2/SCSI peripherals (excluding 9-tracks) sense the AC power line
voltage and automatically configure for either 110vac or 220vac operation.

Unfortunately, a noisy 110vac power line can, and has, cause the power 
supply to attempt to reconfigure itself to 220vac operation. When this
occurs, the power supply is unable to sustain the correct output
levels, and it shuts down. 

Once powered down in the manner described above, the supply must be
manually reset to its 110vac configuration before it will again operate 
properly. This is because once configured for 220vac operation, the
power supply is not allowed to automatically change to a lower
voltage.

Manual reset of a power supply is accomplished by a physical disconnect
from the AC power line for a minimum of two minutes ( five minutes is
recommended ). Physical disconnect is absolutely required; the on/off
switch on the power supply will not effect a physical disconnect as
the sensing circuits are wired in front of the switch.

Troubles diagnosed to this condition are likely to occur again (the
power supplies themselves are in spec). A permanent solution is however
available  at this time through Tier 4 support in Lisle. A call to
Tier 4 support on 1-800-222-9333 will result in either a mail out of 
a power supply hardwired for 110vac operation or instructions for local
modifications where repair facilities are available.

Please take immediate steps to distribute this information to all DSO
personnel involved in servicing the 3B2 product line. Questions may
be referred to me at (201) 898-6832 [RNX 964]. Thanks.
-- 
*  Men Make Plans		    -        And GOD Laughs                   *
*  W.G. (Bill) Simeon               |        d1wxs@nyfast.ATT.COM             *
*  AT&T Remote Systems Engineer	    |        attmail!wsimeon                  *
*  New York City, NY                |                                         *