Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!sdd.hp.com!wuarchive!uunet!beartrk!ceilidh!dnichols From: dnichols@ceilidh.beartrack.com (DoN Nichols) Newsgroups: comp.sys.3b1 Subject: Re: Different boot problem... Keywords: 3b1 boot Message-ID: <1991Mar2.012707.17438@ceilidh.beartrack.com> Date: 2 Mar 91 01:27:07 GMT References: <12744@helios.TAMU.EDU> <1991Mar1.045750.19952@i88.isc.com> <12877@helios.TAMU.EDU> Distribution: comp Organization: D and D Data, Vienna, VA. Lines: 40 In article <12877@helios.TAMU.EDU> n138ct@tamuts.tamu.edu (Brent Burton) writes: >Well, another update to the adventure. > [ ... ] >We tried 2 other times with failure. Then, we decided to check the power >supply voltages and the machine booted (this is insane). Two other >attempts at rebooting worked fine and it's running right now!!! > >The power supply is providing the following: > >spec'd voltage actual >------------- ------ > +5.0V 4.97 > +12.0V 11.95 > -12.0V -12.00 (taken with new digital meter) > >Where should these values lie and when I need to adjust them, which >pots on the ps board do I mess with? (so many pots, so little patience) Only the +5V and +12V are adjustable. Probably you should aim to be a "lettle grey cells" (oops, a little high - watching too much Poirot :-). Probably +5.1 and +12.2. The pots ARE labeled, but the labels tend to be hard to see from any reasonable angle of view. Looking at a 3B1 power supply, +12V is near the center of the multi-pin output power connector, and +5V (R-108) is near the inboard end of the same connector, with its label under a yellow and a black wire, and the curve of U1 (whatever that is - maybe an opto-isolator :-). If you ever HAVE to adjust the -12V, do it by replacing U101 (the regulator chip). Good Luck DoN. -- Donald Nichols (DoN.) | Voice (Days): (703) 664-1585 D&D Data | Voice (Eves): (703) 938-4564 Disclaimer: from here - None | Email: --- Black Holes are where God is dividing by zero ---