Date: Wed, 27 Jan 88 08:58:58 est
From:
[email protected] (Bob McGwier)
To:
[email protected]
Subject: 56K modem fixes
56 kilobaud modem bug report (1-10-88)
TRANSMITTER ENCODER BOARD (110386):
Some of the 110386 transmitter encoder boards have a missing
trace between U10 pin 21 and pin 24. This problem exists only in
the second batch of boards and was due to tape falling off the
artwork. To fix it just solder a wire between U10 pin 21 and 24.
RECEIVER DECODER BOARD (021987 rev A):
There have been reports that various brands of 555 timer
chips don't work well (or at all) in socket U7. I have discoverd
the cause of this problem. The ground side of capacitor C1 needs
to be DIRECTLY connected to pin 1 of U7. You need to cut the
trace that goes between component carrier N1 pin 9 and ground.
Solder a wire from N1, pin 9 to U7 pin 1. All non-CMOS 555 chips
should work with this mod. The next release (rev B) will have
this fixed.
from Dale A. Heatherington WA4DSY
