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Last updated: January 24, 2003
1. Prevent High Frequency Clock From Locking UpLarry Hendry has a great modification to protect the high frequency VCO from locking up when negative voltages are applied to the DELAY and EXT MOD inputs. His solution is much simpler than the precision diode circuit I came up with, so I opted to install the Larry-fix in both of my Time Machines. Added 1K 1% resistor in series with R11 and added two 1N4148 diodes in series to ground (at the same junction). Even if -10 volts is pumped into either the DELAY or EXT MOD input, the voltage at the junction of R11 and the diodes rises to a maximum of 1.4 volts. With this modification, the high frequency VCO maxes out at about 520 KHz on both of my Time Machines. |
2. Add Manual Bypass SwitchPerformed Dave Bradley's modification for adding a manual bypass switch to the Time Machine. Larry Hendry kindly provides additional information and pictures on how to make this same modification.
Dave Bradley's Time Machine modifications. |