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Old 09-25-2014, 12:26 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
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Join Date: Aug 2011
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Eric,
Seeing only positive supply voltages to these stages, I used to wonder how there could be a negative DC voltage on the grid G1 of the HOT or in your case, the oscillator. Normally when you measure an AC sinewave (linear with no DC offset component) with a DC meter, you will get zero because there is an equal amount of voltage above and below zero reference.

The negative voltage is the average DC voltage of the non-linear sawtooth. A majority of this voltage is below the zero crossing, a clue that the oscillator is running if you don't have an oscilloscope.

With all the parts we replace, its no wonder this happens.

Congratulations!
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