158

146

BLT looped at 111 because of ill
men. reff.

MYSTERY -
will return

SRR

2400 4 Jan 68

Sarting [sic] around 1750 started getting
mysterious deaths in the system.
Got random errors in diagnostics
especially part 5 which had consistent
problems with simulated results not
agreeing with each other.

Eventually we got a solid dropping of
bit 11. Traced it to 6205 in 20E18
(bit 11) pin was intermittent. Removed
buss stripping from 6205's for L 1/2
found 6205 in 2011 loose. Found
4 cold soldered joints on 6205 in 2DE 18
explaining the dropping of bit 11 and
the famous MI bit 11 bug. Found
several questionable solder joints on connector
buss wire on a spare 6205 and the
one in 2DE 11. Resoldered
all buss wire to PC board connections on
the 3 modules. Reinserted boards.
Discovered that the buss strips on back
of 6205's are insidiously different.

In both cases the 2 ground leads
together are on the bottom.