Date: Mon, 6 Dec 1999 20:06:26 +0100 (CET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: mjacob@feral.com Cc: kbyanc@posi.net, jkh@zippy.cdrom.com, dseg@texar.com, billf@chc-chimes.com, rfg@monkeys.com, freebsd-hackers@FreeBSD.ORG Subject: Re: Strange SCSI sickness Message-ID: <199912061906.UAA01101@yedi.iaf.nl> In-Reply-To: <Pine.BSF.4.10.9912051441160.28920-100000@beppo.feral.com> from Matthew Jacob at "Dec 5, 1999 2:42:55 pm"
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As Matthew Jacob wrote ...
>
> > Another interesting cause for problems is duff powersupplies. As the
> > proverb goes "every machine is as good as it's PSU". E.g. I just struggeled
> > with a DLT tape unit that inexplicable reset itself. After examining the
> > 5Volts rail with a scope I found glitches on it whenever the drive did a
> > bit of rewinding (dropping out of streaming mode). Had me stumped for a
> > while.
> That's pretty rare these days. It used to happen all the time when
> switching power supplies first appeared (motorboating is what we called
> it), but even recently I had a marginal supply that supplied 4.4VDC-
> *just* enough to function *most* of the time.
This was a DLT4500 5 cartridge changer. I've seen multiple failures
similar to this one due to degraded electrolytic output caps that made
the feedback circuitry of the switching PSU unhappy. DLT4500 has it's
PSU stashed away in an ill ventilated spot, the fact that the heatsinks
are close to the output caps does not help either. Heat tends to kill
electr. caps.
Anyway, the topic at hand is more suitable for -hardware (or so) I guess.
Wilko
--
Wilko Bulte Arnhem, The Netherlands - The FreeBSD Project
WWW : http://www.tcja.nl http://www.freebsd.org
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