DRIFTING HW-101

[Bill Coleman]

On Jun 21, 2007, at 10:27 PM, Kenneth G. Gordon wrote:

> However, it is an extremely simply project to build a 12 VDC power
> supply using the filament voltage as an AC source and regulate the DC
> output, then feed THAT voltage to another LM-317 or something like it
> to provide the twice-regulated 8VDC to run the FET with.

Regulating twice seems like real overkill. An LM7808 should do a more  
than adequate job in one step.

Zener or VR tube regulation is tricky, as the current range for good  
regulation is narrow. Draw too much current (or have the series  
resistor value change to a greater value with age or overheating),  
and you lose regulation. Draw too little current (or have the series  
resistor decrease in value due to some internal value) and you can  
overheat the regulator.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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