Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!scooter!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.amiga
Subject: Re: B2000 power supplies
Summary: Sounds like the over-voltage crowbar is getting you
Keywords: power supply repair 90 day warranty
Message-ID: <1613@neoucom.UUCP>
Date: 3 May 89 14:04:41 GMT
References: <3285@hplabsz.HPL.HP.COM>
Distribution: na
Organization: Northeastern Ohio Universities College of Medicine
Lines: 25


Many switch-mode power supplies will not run correctly unless a
proper load it attached.  If you take the power supply out of the
machine for bench examination it is likely that the operation will
be erratic.

If the 5 volts is coming on, then clamping down to about a volt
after a few seconds *with the mother board attached*, it sounds
like the over-voltage crowbar protection is shutting down the power
supply.

How close is the 5 volt output to 5.00 volts?  Check it with a
decent digital meter.  Don't use a $5.95 ArcherKit piece of junk to
measure it.  If the voltage is too high, adjust the the voltage pot
carefully (if you can locate it).  I don't have a B2000, but I'd be
willing to bet there is a 5 volt adjustment pot lurking in there
somewhere in the power supply.

If you don't know what you're doing, by all means take it to a
decent repair center and let them fix it.  Remember if you poke
around in the power supply, you might be electrocuted.  Don't take
chances.

Bill
wtm@impulse.UUCP