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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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8th Nov 2018, 10:41 pm | #21 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Playing with valve oscillators
This is an oscillogram of the LC oscillator output at 25 kHz. Sweep is set at 20uS/div and amplitude is set at 20V/div. What seems to be a crossover distortion is in fact a flaw of the oscilloscope that I've been too lazy to solve.
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When electrons move, things happen. There's nothing you can do that can't be done. |
9th Nov 2018, 6:43 pm | #22 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
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Re: Playing with valve oscillators
Passive circuit with gain greater than one.
I assume that the phase shift is zero. There is an old book by Dean (p197) which I cannot find. This used a pair of pnp transistors in a Darlington pair to get high input resistance and low output resistance. There were three capacitors in series, two were driven by 47k resistors, the third went to the transistor base. With C=80microF, 1cycle/minute With C=100nF, 11Hz I believe this low frequency system was used to generate vibrato in electronic organs. |
10th Nov 2018, 6:32 pm | #23 | ||
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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Re: Playing with valve oscillators
Quote:
See photo below, which'll make things clearer. So with a cathode follower having a gain > 29/30, you can make it oscillate! |
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19th Nov 2018, 6:36 pm | #24 |
Heptode
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 617
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Re: Playing with valve oscillators
An update for today.
Both oscillators are already mounted and running. I will need to apply some decoupling as signal are appearing on each other.
__________________
When electrons move, things happen. There's nothing you can do that can't be done. |