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From: Bob Mc Gwier Subject: 56K Modem Fixes And 56K Modem Bug Report 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 discovered 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 |
