yes, the zener string voltage looking at the gates of the mosfets minus about 4 volts is the source voltage.....this is the design, and changes in line voltage will keep the output voltage constant with load...
your load being a class A, will never vary, so i wonder, a crcrc filter would have been better,
thus far i have resisted the urge to use voltage regulators in my tube amps...
but this one being a mosfet source follower can be an exception, having no voltage gains by itself and all.....carry on....
your load being a class A, will never vary, so i wonder, a crcrc filter would have been better,
thus far i have resisted the urge to use voltage regulators in my tube amps...
but this one being a mosfet source follower can be an exception, having no voltage gains by itself and all.....carry on....
The fet is voltage controlled (electric field), so no current or power goes through the gate. Like a tube.
https://www.ti.com/lit/an/snva008/s...20736&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/an/snva008/s...20736&ref_url=https%3A%2F%2Fwww.google.com%2F
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the drain source terminal is like a variable power resistor that changes its resistance in reaction to a voltage at its gate...
putting in a new or fresh mosfet is not entirely a bad idea...
without the mosfet in circuit, you can measure the voltage across the zener strings, that will be the voltage at the gate of the mosfet...
patience is a virtue here...
Thanks for all the input.....
I did watch a few videos on how MOSFETs work but my brain just can't work it out.
I have already taken a few measurements. Ok maybe I shouldn't try and understand it as its beyond me but I'm just trying to find out what is wrong with the voltages!
I did watch a few videos on how MOSFETs work but my brain just can't work it out.
I have already taken a few measurements. Ok maybe I shouldn't try and understand it as its beyond me but I'm just trying to find out what is wrong with the voltages!
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It's after the 1.5M for sure, and is more likely to be a short than an open.
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Progress!!............
ZD204 tested perfect in circuit but after replacing it the unit powered up!
Unfortunately it only lasted about 5 minutes before both the Zeners blew.
Both LZD204 and ZD204 made a loud snapping noise and now the meter on diode mode gives me reading in both direction where previously it didn't.
Any suggestions what would cause it to blow? I have made progress in at least getting it to work but now need advice on what what cause the Zener to blow like that.
As always any advice appreciated!
ZD204 tested perfect in circuit but after replacing it the unit powered up!
Unfortunately it only lasted about 5 minutes before both the Zeners blew.
Both LZD204 and ZD204 made a loud snapping noise and now the meter on diode mode gives me reading in both direction where previously it didn't.
Any suggestions what would cause it to blow? I have made progress in at least getting it to work but now need advice on what what cause the Zener to blow like that.
As always any advice appreciated!
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