1 May
2023
1 May
'23
11:29 p.m.
On May 1, 2023, at 6:23 PM, Brent Hilpert via cctalk
<cctalk(a)classiccmp.org> wrote:
On 2023-May-01, at 2:25 AM, Peter Coghlan via cctalk wrote:
The usual DEC spec for power supplies was +/- 5%. In reality there occasionally were
issues: FS told me on one occasion when we had DMC-11s not working right that those
actually need +5%, -0%, and that FS people knew this and would adjust power supplies as
needed.
paul
It seems a bit odd that a power supply from
someone like DEC of that era would
be designed to depend so critically on the absolute value of a rail used
for startup purposes.
Further to Peter's point above, the 1988 NatSemi databook - which is to say, from the
era of this power supply - specs the 7812 output min-max to be 11.4 to 12.6V (+/-5%). Your
measured Vstart=12.4V is well within this.
Looking at the schematic, nothing stands out where the distinction from 12 or 12.1 would
matter.