DEC-423 to RS-232 chip?

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Sun Dec 31 13:24:03 2000

Hello Everyone,

I had one of those DEC MMJ->DB-25 things come apart on me and expected to
see the MMJ connector wired to the DB-25 in the now familiar mode we see in
the FAQ, however instead there is an ST 20 pin chip betwixt the MMJ and the
DB25! This might explain why they work better than the wired together
solution :-)

The chip is labeled HTAM1B4 (looks like a house number) then under that is
P 9236 (date code I suspect) and then under that "Philippines".

Can anyone guess the "real" part number for this chip? no power or passives
at all so I presume it runs on phantom power. looking at the PCB I'd guess
its wired up as follows:

pin
         1 - GND 20 - GND
         2 - MMJ-5 19 - DB-2
         3 - MMJ-2 18 - DB-3
         4 - MMJ-6 17 - DB-20
         5 - MMJ-1 16 - DB-7
         6 - GND 15 - GND
         7 - GND 14 - GND
         8 - MMJ-4 13 - DB-8
         9 - MMJ-3 12 - DB-8
        10 - GND 11 - GND

The DB25 is a female (DTE?) and while I'm sure of the DB pin numbers the
MMJ numbers may be reversed, since I'm never sure if pin 1 on the MMJ is
the left pin looking into the connector body or the right pin. (I assume
the left pin above)

--Chuck
Received on Sun Dec 31 2000 - 13:24:03 GMT