23 Aug
2014
23 Aug
'14
1:55 p.m.
On Sat, Aug 23, 2014 at 12:56 PM, drlegendre . <drlegendre at gmail.com> wrote:
This machine has a Processor Tech. MB-1 mainboard in
it. Full-width, 16
slots, and some mods I don't understand.
First, there's an LM309 (TO-3 case) mounted to the board, apparently
providing reg'd 5VCD to the normally 8V (un-reg'd) line. Why would that be
there? Every plug-in board I've seen - which isn't all that many,
admittedly - has its own regulator for 5V on-board.
Secondly, on the far left side of the board, there are several columns of
resistors that seem to be doing a couple different things - some are
pulling-up various groups of lines to what seems like 1/2 of VCC, others
are either there for termination or some other unknown function.
Are you sure the LM309 doesn't have its input tied to the 8V supply,
and its output to those termination resistors?