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Author Topic: Investigating "anomalies" in Bifilar coils  (Read 220904 times)
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It's turtles all the way down
Hi Partzman and all,

I wonder whether you have already considered to test your bifilar coil circuit to embed into a looped circuit?

IF not yet, then I would propose to build a simple one transistor oscillator that would have a normal output coil inductively coupled to the main oscillator LC tank circuit and would feed your bifilar coil circuit as the FG does now. 
And at the output of your bifilar coil circuit a full wave bridge rectifier (made from say Germanium diodes) would drive a DC voltage stabilizer, this latter should have very low idling current of course. Then the output of this DC stabilizer would drive the one transistor oscillator. Such simple looping would eliminate any measuring issues... if there are any, that is. 

The DC voltage level for the one transistor oscillator could easily be chosen to be very close to the output DC level of the stabilizer (chosen strategically) so that a linear, micropower regulator could be used without too much loss.

With the COPs around 1.5 to 3 or so as the present measurements indicate, such looping should be possible and even if the power levels involved are in the some ten to some hundred mW range, that would be enough to maintain the operation of the looped circuit, perhaps even a dimly lit LED could be run from it.

Gyula

Looping is always the final proof. I have explored circuits as Gyula proposed and it is one good way, but can be too lossy if COP's are not high enough to account for all losses in the loop. As Gyula states you will need some COP of 1.5 to 3.0 with perhaps a minimum of 1.2 to 1.3 if you are careful with your DC to DC converter design. I have outlined some efficient looping schemes on my bench.

But there is another less lossy way, and that would involve direct looping with appropriate phase tuning network from output to input. Also a 1:1 common mode choke can be used if isolation is required, the important thing is that the output phase be tuned to exactly correspond to the input phase, and make sure the phase tracks as parameters change slightly when a load is applied that causes the wire to heat up and add extra resistance.

Hypothetically, a passive system that runs with a very small power gain could start on thermal noise, or the swipe of a magnet, and not even need a signal generator for startup.

Far fetched? I think SM would disagree. In one of the videos, we see SM waving a speaker magnet around one unit that wouldn't quite start up while DR. Schinzinger observes.


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After a fresh calibration, these are the signals from my current probe (green) placed between the resistors R1 and R2 (17.36mA rms) and the yellow
probe placed across the R2 resistor (19.36mA rms).

This is with the same setting from my FG (20Vpp sine wave @ 190KHz) as used before.

The yellow signal is kind of weak, so the between vertical cursor test is not very stable.

Itsu

Itsu,

There is a little offset in the probe output but the phase looks close with the probe perhaps with a very very slight lead.  So if I understand your results here, your probe would be reading 17.36/19.36 = 89.67% of your sense resistor measurement which would make your Pin conservative thus decreasing your COP if corrected.  Have you re-run a test since your calibration?

Edit: I see you posted results while I was typing this- thanks.

Pm
   
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Using a different TBP coil (with similar properties) i redid my measurements using the same 51 Ohm and 1 Ohm resistors.

Input calculated by the scope/current probe is 22.7mW.
Input calculated by using the R2 current is: 6.81V rms * 0.0189mA rms * cos -80° =  22.3mW
See screenshot 1

Output calculated by scope is 15.4mW
Output calculated by Ch3 (purple)² / 52 Ohm = 0.8682² / 52 =  14.49mW
See screenshot 2

So this different coil also shows via 2 different methods a similar cop<1 as the first TBP coil.

 
Itsu

Itsu,

I'm really not surprised you are not seeing a COP>1 at this low frequency ~200kHz.  If you raise the input frequency however, the COP should increase until you reach COP>1.  This should occur without the phase angle decreasing as seen on your previous test but if not, I'm not sure as to what the reason might be at this point!

Pm
   
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Looping is always the final proof. I have explored circuits as Gyula proposed and it is one good way, but can be too lossy if COP's are not high enough to account for all losses in the loop. As Gyula states you will need some COP of 1.5 to 3.0 with perhaps a minimum of 1.2 to 1.3 if you are careful with your DC to DC converter design. I have outlined some efficient looping schemes on my bench.

But there is another less lossy way, and that would involve direct looping with appropriate phase tuning network from output to input. Also a 1:1 common mode choke can be used if isolation is required, the important thing is that the output phase be tuned to exactly correspond to the input phase, and make sure the phase tracks as parameters change slightly when a load is applied that causes the wire to heat up and add extra resistance.

Hypothetically, a passive system that runs with a very small power gain could start on thermal noise, or the swipe of a magnet, and not even need a signal generator for startup.

Far fetched? I think SM would disagree. In one of the videos, we see SM waving a speaker magnet around one unit that wouldn't quite start up while DR. Schinzinger observes.

ION,

Could you give an example of how this phase tuning might be achieved.  There is also normally a difference in output voltage level that is lower than the input voltage so this would have to be compensated for as well.

Thanks.

Pm
   

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Itsu,

I'm really not surprised you are not seeing a COP>1 at this low frequency ~200kHz.  If you raise the input frequency however, the COP should increase until you reach COP>1.  This should occur without the phase angle decreasing as seen on your previous test but if not, I'm not sure as to what the reason might be at this point!

Pm

When increasing the frequency and to obtain again a -80° phase shift between input voltage and current i have to go all the way to 26MHz.
Doing again the measurements there i get:

input measured by current probe/scope 7.689mW
output Ch3 (purple)² / 52 = 1.26² / 52 = 30.5mW
Cop = 3.9

But i really do not trust these figures at this frequency

Itsu
   
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When increasing the frequency and to obtain again a -80° phase shift between input voltage and current i have to go all the way to 26MHz.
Doing again the measurements there i get:

input measured by current probe/scope 7.689mW
output Ch3 (purple)² / 52 = 1.26² / 52 = 30.5mW
Cop = 3.9

But i really do not trust these figures at this frequency

Itsu

I would agree.  What you might try is to find the resonant frequency of the coil assembly as connected with load and all, and then go lower to a frequency that is about 60-70% of the resonant frequency and see what the results are.

Pm
   

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You cannot make a length of rope tight by pulling on one end,while the other end is not fixed (grounded)
Untied rope does not behave like an untied coil.

All the current flowing from the source(FG),must pass through R2-there is no other path for the current to flow through.
There is - through displacement current.

If you remove R2,and connect the ground to R1,then you have just altered the circuit.
With that change (shown on the lower schematic below), only the polarity of the Ch2 signal will be inverted and the voltage drop of R2 will not be included in the input voltage.
This probe placement constitutes an improvement of the power measurement technique - not an alteration of the working circuit.
   
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ION,

Could you give an example of how this phase tuning might be achieved.  There is also normally a difference in output voltage level that is lower than the input voltage so this would have to be compensated for as well.

Thanks.

Pm

I'm working on some schematics for this. If the voltage is lower than input, then the current must be higher if it truly has a COP=>1. There are a few ways to do a passive loop back. I'm working on using a matching transformer or autotransformer with slight step up for V so the output can pump current into the input and also adding a phase correction device.

I haven't been following too closely  the tests you guys have been doing , as I was working on the other project. How much phase correction is actually needed for the highest COP device? And which direction?

What I was getting at is this: a DC loopback is not really needed for an AC system. You don't need to go through all those conversions. If the system indeed has an AC power gain, it can be looped in the AC domain if you are careful about phase and provide a correct impedance match, as long as the input and output frequency are the same. This should have much less loss as it would only involve a small variable capacitor or variable inductor depending on the requirement of lead or lag.

I'll post some schematics soon.

Regards



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Untied rope does not behave like an untied coil.
There is - through displacement current.
With that change (shown on the lower schematic below), only the polarity of the Ch2 signal will be inverted and the voltage drop of R2 will not be included in the input voltage.
This probe placement constitutes an improvement of the power measurement technique - not an alteration of the working circuit.

The lower schematic is a cleaner connection layout for measurements but the signal generator must have isolated ground or an isolation transformer could be used on the input.  I used to use this method of connection with an iso transformer but ended up liking the current connections better.

Pm
   
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I'm working on some schematics for this. If the voltage is lower than input, then the current must be higher if it truly has a COP=>1. There are a few ways to do a passive loop back. I'm working on using a matching transformer or autotransformer with slight step up for V so the output can pump current into the input and also adding a phase correction device.

I haven't been following too closely  the tests you guys have been doing , as I was working on the other project. How much phase correction is actually needed for the highest COP device? And which direction?

What I was getting at is this: a DC loopback is not really needed for an AC system. You don't need to go through all those conversions. If the system indeed has an AC power gain, it can be looped in the AC domain if you are careful about phase and provide a correct impedance match, as long as the input and output frequency are the same. This should have much less loss as it would only involve a small variable capacitor or variable inductor depending on the requirement of lead or lag.

I'll post some schematics soon.

Regards

ION,

Great, but you might keep this in mind that with one 5-coil design, the output voltage was 4.396v rms while the input was 3.497v rms and they were in phase but the current was leading by ~40 degrees.  The COP was ~1.22 and I did try to loop this design with direct connection from output to input but did not fly!  So with a low loss phase correction scheme.........?

Pm
   

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The lower schematic is a cleaner connection layout for measurements but the signal generator must have isolated ground or an isolation transformer could be used on the input.
Yes, if the scope and the signal generator share a common ground then R2 will become shorted through that common path.

A HE current probe provides isolation and because of that, it can be placed on the wire connecting the signal generator with L1.
When using such an isolated current probe, the resistor R2 can be deleted altogether.  I also recommend placing this current probe (Ch2) PHYSICALLY BEFORE the voltage probe (Ch1). All of this is shown on the schematic below.

« Last Edit: 2017-05-01, 23:49:18 by verpies »
   
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Gyula,

I have considered looping the device in the past but have not done so however, your idea certainly has merit and should be given a try.

Pm

Hi Partzman,

One more question if I may:  do you think your circuit would behave in the same way if the output would be taken from a third coil, L3,  coupled to L1 & L2?  I mean making a trifilarly wound coil instead of the bifilar one.  This needs to be tested of course if you or someone else have not done so.

EDIT:  I may have asked a silly question...  because the "upper" end of L2 should be dealt with? and it may modify circuit behaviour.

Thanks,
Gyula
   
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Hi Partzman,

One more question if I may:  do you think your circuit would behave in the same way if the output would be taken from a third coil, L3,  coupled to L1 & L2?  I mean making a trifilarly wound coil instead of the bifilar one.  This needs to be tested of course if you or someone else have not done so.

EDIT:  I may have asked a silly question...  because the "upper" end of L2 should be dealt with? and it may modify circuit behaviour.

Thanks,
Gyula

Gyula,

Not a silly question at all. 

In all my testing I have used sandwiched pancake coils from 2 to 7 in number.  In a 3 coil arrangement for example, when the center coil is the primary, the distributed capacitance is double the 2 coil and the inductance varies depending on whether the secondaries are in series or parallel.  With 5 coils you can have 2 primaries with 3 secondaries or 3 primaries with 2 secondaries, etc.  These combinations allow for various ratios of L/C to be achieved depending on the frequencies one desires.  The secondaries can also be cross coupled, shorted, resonated, loaded, or in combination.

Pm 
   
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Gyula,

Not a silly question at all. 

In all my testing I have used sandwiched pancake coils from 2 to 7 in number.  In a 3 coil arrangement for example, when the center coil is the primary, the distributed capacitance is double the 2 coil and the inductance varies depending on whether the secondaries are in series or parallel.  With 5 coils you can have 2 primaries with 3 secondaries or 3 primaries with 2 secondaries, etc.  These combinations allow for various ratios of L/C to be achieved depending on the frequencies one desires.  The secondaries can also be cross coupled, shorted, resonated, loaded, or in combination.

Pm

To further complicate the number of variables, you could also treat the "pancakes" in the "coil sandwich" as elements of a capacitor compression type trimmer.....who knows how changing the spacing slightly between the sandwich layers will affect the output?

And while were at it, how do we know what type of spiral would give better results? Would varying the pitch of the spiral tune the layer to layer capacitance in a positive way? There are numerous spiral types.

https://en.wikipedia.org/wiki/Spiral

Regards



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"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
   
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The question that is foremost in my mind right now is why Itsu isn't getting similar results to mine. His coil, as far as I can tell, is very similar to mine. I can understand why/how a current probe might give different results but when he uses a direct voltage probe connection to the 1 ohm resistor he still isn't getting comparable results. Is my scope simply lying to me? It wouldn't be the first time. One thing I've noticed in Itsu's traces is that the Math trace is mostly all positive, except in that very high frequency trial where he finally did get a COP>1.

However I don't even rely on the math trace of my scope any more, I perform the calculations of input power manually using V p-p x 0.3535 to give Vrms, which usually agrees quite closely with the Period Vrms reported by my scope, and as far as I can tell there is no scope error there. The Rigol's RMS bug has been fixed in the latest-but-one firmware update and no longer causes problems with channel crosstalk or erroneous readings from disconnected channels. Again, the basic peak-to-peak voltage values of the scope traces are accurate as far as I can tell and these form the basis of most of my calculations. There is some uncertainty in my scope's reported phase angles but by "eyeball" and also by calculation they seem to be reasonable if not quite exact all the time.

I also find it hard to believe that the small inductance of my 49.58 ohm metal film resistor stack could be skewing my results enough to give the numerical results I'm seeing. Why is it so easy for me to get the results from calculation, when Itsu can't get comparable results at the same low frequencies that I'm getting, since his coil is quite similar to mine in electrical parameters? Is there some really delicate "sweet spot" of coil construction that I just happened to hit? What then about my solenoid results, where I also found it quite easy to get the "OU" numbers?

I  must be doing something wrong over and above any other systematic errors caused by incorrect probing in the original schematic. But what could it be? I can't quite see it all being down to the Rigol's reported numbers, somehow.

My next testing, later on this evening, will be to replace the 49.58 ohm metal-film resistors with a 9.4 ohm non-inductive resistor pair in to-220 package, and to replace the 1 ohm non-inductive CVR with a similar Ohmite noninductive 0.1 ohm value. 

   
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Just to be sure I'm not making some silly error in connections, I've enlarged the connection area of my test setup. Could you all please take a close look and see if I've done anything wrong with the connections? Comments and questions appreciated.

   
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Well.... So I replaced the 49.58 ohm metal-film resistors by 2 ea. 4.7 ohm 1 percent non-inductive resistors in TO-220 packages, in series, back-to-back, for a total of 9.4 ohms. And I replaced the 1.00 ohm Ohmite NI with a 0.100 ohm Ohmite precision NI. And sure enough, this made the "OU" results much more difficult to obtain, with testing at various frequencies using the F43 at high output running at COPs of 0.5 to 0.8 or so depending on frequency. And I had to go much higher in frequency to get phase shifts in the -75 to -85 degrees or so.

BUT.... at about 3.034 MHz I achieved a phase shift of around -87 degrees and got a COP result that is in the "OU" range.

Using the Rigol's PeriodRMS values:

IN: 3.29 Vrms x 0.908 Arms x cos -87.27 = 142.3 mW
OUT: (1.92 Vrms)2/9.5 = 388.0 mW
COP  2.72

... and the 9.4 ohm TO-220 resistor stack is definitely heating up a good bit.

   
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Now... since cos(phase angle) tends rapidly towards zero as (phase angle) approaches + or - 90 degrees.... and one can apparently "dial in" pretty much any phase angle by selecting frequency.... what does this mean? Can you arbitrarily set your COP simply by selecting a frequency that gives a phase angle approaching 90 degrees? What if I set a frequency that gives exactly -90 degrees of phase shift? Does this mean input power goes to zero and COP goes to infinity?

Furthermore, what accounts for my changed results now that I am using a lower resistance and non-inductive resistors for R1? Is the fact that it is much harder to get COP > 1 due to lower resistance, or lower inductance, or both? If stray or parasitic inductance is responsible for the COP > 1 effect.... well, assuming the OU is real, what's the problem? Maybe "realni OU" requires this added inductance, stray or parasitic or deliberately introduced. Or... assuming the OU is not real... then can _all_ of our COP>1 results be attributed one way or another to stray or parasitic inductances introduced by even the best probing methods, or coil layout, or other factors we haven't considered?


"They are just questions, Leon...."

http://www.youtube.com/watch?v=Umc9ezAyJv0
   

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However I don't even rely on the math trace of my scope any more,
If one is not careful with the channel analog gains, multiplying 2 channels can multiply quantization errors of 2 undersaturated ADCs.

I perform the calculations of input power manually using V p-p x 0.3535 to give Vrms,
That is a correct method IF the waveforms are perfectly sinusoidal.

...since cos(phase angle) tends rapidly towards zero as (phase angle) approaches + or - 90 degrees....
This calculation is correct IF the phase-shifted waveforms are perfectly sinusoidal, too.
   

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Just to be sure I'm not making some silly error in connections, I've enlarged the connection area of my test setup. Could you all please take a close look and see if I've done anything wrong with the connections? Comments and questions appreciated.

TK,

as far as i can see, i have the exact same setup, providing that the red winding is the most outer to start with (can't really see that).

As i have used 2 similar TBP coils, i could start using different resistors to see if there is a change there like you noticed.

Itsu
   

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Now... since cos(phase angle) tends rapidly towards zero as (phase angle) approaches + or - 90 degrees.... and one can apparently "dial in" pretty much any phase angle by selecting frequency.... what does this mean? Can you arbitrarily set your COP simply by selecting a frequency that gives a phase angle approaching 90 degrees? What if I set a frequency that gives exactly -90 degrees of phase shift? Does this mean input power goes to zero and COP goes to infinity?

Furthermore, what accounts for my changed results now that I am using a lower resistance and non-inductive resistors for R1? Is the fact that it is much harder to get COP > 1 due to lower resistance, or lower inductance, or both? If stray or parasitic inductance is responsible for the COP > 1 effect.... well, assuming the OU is real, what's the problem? Maybe "realni OU" requires this added inductance, stray or parasitic or deliberately introduced. Or... assuming the OU is not real... then can _all_ of our COP>1 results be attributed one way or another to stray or parasitic inductances introduced by even the best probing methods, or coil layout, or other factors we haven't considered?


"They are just questions, Leon...."

http://www.youtube.com/watch?v=Umc9ezAyJv0

With the lower value resistor's,more current would now flow through L2.

L1 and L2 have a capacitive/inductive relationship.
If the value of the inductive coupling is raised,by means of a greater magnetic field,due to the higher current flow,while the value of capacitance remains the same-would this upset the apple cart ?-so to speak

Maybe to once again bring the two back into balance,you have to raise the frequency >

Just thoughts.

Im hitting the workshop to find my long solenoid coil,and wind the second coil over the top of the first.


Brad


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Hi Partzman,

Thanks for your additional info. 

I have devised a schematic to show how I mean to embed your bifilar coil circuit into a looped circuit, see attachment.  Of course, several solutions exist for the one transistor oscillator or to use an off the shelf micropower voltage regulator or a DC-DC switch mode converter.
In the oscillator I choose to work around 1 MHz, a 500 pF variable capacitor, labeled as C, can be used to tune the LC tank and find COP>1 frequencies.  AM pocket radio coil components like oscillator or IF stage coils can be adapted here.
In the lower left corner of the schematic I indicated to chain two bifilar coils in a hope it may be able to further increase output power, it is possible that a tuning capacitor would be needed across the second bifilar to help some matching or influence overall phase shift.

Maybe it is still too early to devise such looping circuit but there is a new replication at overunity.com
http://overunity.com/17186/the-bifilar-pancake-coil-at-its-resonant-frequency/msg505815/#msg505815
so things are promising...   :D

Thanks,
Gyula

Gyula,

Not a silly question at all. 

In all my testing I have used sandwiched pancake coils from 2 to 7 in number.  In a 3 coil arrangement for example, when the center coil is the primary, the distributed capacitance is double the 2 coil and the inductance varies depending on whether the secondaries are in series or parallel.  With 5 coils you can have 2 primaries with 3 secondaries or 3 primaries with 2 secondaries, etc.  These combinations allow for various ratios of L/C to be achieved depending on the frequencies one desires.  The secondaries can also be cross coupled, shorted, resonated, loaded, or in combination.

Pm
   
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TK,

as far as i can see, i have the exact same setup, providing that the red winding is the most outer to start with (can't really see that).

As i have used 2 similar TBP coils, i could start using different resistors to see if there is a change there like you noticed.

Itsu

Well, I had to look with a magnifying glass for 10 minutes to make sure, but it looks like I got a half-twist right at the start of the winding where it goes through the tiny holes in the disk, and the "Red" winding is actually the second layer, not the outermost one.

I can't see how this could possibly make a difference but it wouldn't be the first time that I've been wrong about something like that.

All previous tests had the "output" 49.58 or 9.4 ohm "load" across the "Blue" winding which is the outermost, but I can change it over to the "Red" winding and make the "Blue" winding the input easily enough,  and then repeat the 3.034 MHz test to see if I get the same result or not.

Thinking ahead... I used female header sockets to mount the resistors to the coil's pins, so I didn't even have to warm up the soldering iron to make the changeover.



   

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As TinselKoala has found that both a Solenoid wound and flat wound coil yield similar results how about trying a
" commercially " wound transformer ?

I saw some interesting effects by passing the output from a " modified Sine wave " inverter into the open ended secondaries of a 12/12 to 240 volt toroidal transformer.

Cheers Graham.


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Hi Partzman,

Thanks for your additional info. 

I have devised a schematic to show how I mean to embed your bifilar coil circuit into a looped circuit, see attachment.  Of course, several solutions exist for the one transistor oscillator or to use an off the shelf micropower voltage regulator or a DC-DC switch mode converter.
In the oscillator I choose to work around 1 MHz, a 500 pF variable capacitor, labeled as C, can be used to tune the LC tank and find COP>1 frequencies.  AM pocket radio coil components like oscillator or IF stage coils can be adapted here.
In the lower left corner of the schematic I indicated to chain two bifilar coils in a hope it may be able to further increase output power, it is possible that a tuning capacitor would be needed across the second bifilar to help some matching or influence overall phase shift.

Maybe it is still too early to devise such looping circuit but there is a new replication at overunity.com
http://overunity.com/17186/the-bifilar-pancake-coil-at-its-resonant-frequency/msg505815/#msg505815
so things are promising...   :D

Thanks,
Gyula

That's a good idea. I think the first thing to do would be to test whether the output will still work if the load resistor is removed and the voltage doubler part of the circuit is connected across L2 instead, still using the FG as input oscillator. That part can be tested pretty easily, probably. I've got plenty of 1n34a and 1n60 diodes hiding in my stash (also some small Schottkys in there too I think).
   
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