He's using the 8 Volt regulator to enhance the stability of the SG3525 PWM chips and the CMOS chips as they produce the 3 harmonically related pulse frequencies for maximum accuracy and minimum jitter.
If you're using a 10 Volt regulator in its place it may be failing due to lack of "overhead" in the supply voltage. Analog Voltage Regulators, unless they're the Low Drop Out variety, require an input voltage that is a minimum of 3 Volts greater than the Regulated Output Voltage.
As long as the Input Voltage is 13 or more Volts it will work well. Once the Input Voltage drops to less than 13 Volts the Regulator will be subject to Drop Out or loss of regulation. This should not result in damage to the Regulator since they have protection circuits built in, but it may as the Regulator loses its ability to function normally.
All of the chips in the circuit will operate at up to 15 Volts; so long as the input doesn't go above that the Regulator isn't absolutely necessary. The circuit will function but will lack the precision and stability afforded by the 8 Volt Regulator.
If you don't have an 8 Volt regulator you may use a 7805 configured as an Adjustable Regulator. Do a search for "7805 circuits" to find an example.
You'll be able to make an Adjustable Regulator which will enable setting the Regulated Output Voltage from 5 Volts to about 3 Volts less than the Input Voltage which should be no more than 20 Volts.
Let us know how your experiments progress.Statistics: Posted by SeaMonkey — Wed Aug 20, 2008 4:52 am
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