Different boot problem...
dnichols at ceilidh.beartrack.com
Sat Mar 2 12:27:07 AEST 1991
In article <12877 at helios.TAMU.EDU> n138ct at 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
If you ever HAVE to adjust the -12V, do it by replacing U101 (the
Donald Nichols (DoN.) | Voice (Days): (703) 664-1585
D&D Data | Voice (Eves): (703) 938-4564
Disclaimer: from here - None | Email: <dnichols at ceilidh.beartrack.com>
--- Black Holes are where God is dividing by zero ---
More information about the Comp.sys.3b1