Tempest - Vector Generator RAM

Folks,

        I have a problem with my Vector Gen RAM. I have socketted the RAM
and when booting up in test mode, I get a problem with RAM M3. I replace
this with a known working good 2114 and it still shows up as such (4 short
beeps and then 1 long beep). I conduct some continuity tests and according
to the schematic, I see connections between all appropriate pins on the RAM,
but I can see there is a problem with some of the RAM connections, but I
don't know what to do about it. What I mean is that on the schematic, pins
11-14 on RAMs J3,K3,L3,M3 are DVG3,DVG2,DVG1,DVG0 and J4,K4,L4,M4 are
DVG7,DVG6,DVG5,DVG4 and these behave differently than the address lines.
All the address lines are tied together on the RAMS, but the 11-14 are tied
together in BANKS (the 3's are together and the 4's are together) but they
are both tied to I/04, i/03, I/02, I/01. Here is the problem.... what the
HECK is I/0? Where are these connected? I measure impedance across pins
11-11, 12-12,13-13,14-14 across that I/0? barrier (across the 3's to 4's)
and I get 19K 11-11, 13-13, 14-14, but on pins 12-12, it is an open circuit.
I measure a known good working board and the impedance across all of the
pins above is the same (for all 4 pins INCLUDING pin 12) so I know that
there is something wrong with the connections on that pin, but until I know
*where* the connection is supposed to go, I will not know how to fix it.

        Can anyone shed some light on what the I/0? connections are
referring to?

Much appreciated.

Andrew Evrovski
HPC Development Director
Cyberplex
t: 902.429.4721 ext.109
f: 902.423.0899
www.cyberplex.com

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Received on Fri Nov 24 10:28:45 2000