user TURBO?s replication of Steven Mark?s TPU ?

[otto]

Hello all,

@Aether22

I use IRF840 MOSFETs and had 240V kicks. Before this I used IRF 730 MOSFETs and had only 170V kicks measured with a scope connected at my collector coil.

Once I posted the difference between a IRF730 and IRF840 MOSFET. As I remember the IRF840 has a bigger capacitance at switchin ON. Strange!!

I did this morning new tests with my TPU and here are the results:

my problem is the outer, say, feedback coil.
1. connected in reverse or better to say all control coils are pulsed in the same direction and this feedback coil in the other direction. Bad results!
2. connected this feedback coil all 4 segments in series. Bad results.
3. connected this feedback coil like the others, like the Tesla Patent...Gooood results.

This feedback coil is made of 4 segments...I saw the middle of this 4 segments is very important and so I connected a wire to this middle point and touched every other point in the TPU. The result: my best signal is when I connect this middle point wire to the + plus or to say better to this point where the same coil ends!!! Thats the reason I posted last time this is not for public because I think its an idiotic way to connect this feedback coil but who knows??? I dont!

Today I saw also strange thinks: As Im working always with a light bulb connected with my TPU I wanted to see how the signals looks without the bulb. Ok, they are nice but when I connected my bulb again to the TPU I saw the signals rising. A lot rising!!!! I already have signals over 400V but when I connect my bulb (100W) the smallest and all other signals rises dramatically. There is no difference 40W,60W,100W light bulb. Of course I dont see anymore the biggest signals because they are "out of range" but usually small signals growed up.

As you can see I cant without you!!

Otto

[starcruiser]

Otto,

So the bulb seems to act as part of the feedback loop. Interstesting!

As to the feedback coil, so you are matching the phase, or to say the direction of the coil current with the control  coils? Same wiring as the control coils?

A comment on the MOSFET, I took a look at the spec sheets and it does show a larger capacitance on the Cdg 1300pF for the IRF840 vs 400pF for the IRF510. over all it appears to be about 3 times the capacitance (for all of the other inter connection values as well). Perhaps the off state resistance has something to do with this as well or maybe the inherent inductance of the leads?

[otto]

@Carl,

About the MOSFETs: exactly.
Yes, my feedback coil has the same current direction. I would try to connect a little capacitance to the gate-source or gate-drain connection but hollidays are here, everything closed...my MOSFETs could burn....no dont play with them!!! Look at Grumpys post about MOSFETs!! Its great!!

I think I will buy a lot of various MOSFETs just to see the difference.

Otto

[starcruiser]

Otto,

Thanks for the response. Have you tried to scope the MOSFET output with out them connected to the TPU? Just curious if they show any self oscillation due to the internal capacitance and inductance.

I'll take a look at Grumpy's post on them.

[Grumpy]

otto,

Your diagram shows each collector wired to the control of the next ring...is this correct?   Have you tried with the control coils separate from the collectors?

IRF840 switches much faster than 730.  Look up the datasheets first - don't waste money.  Fairchild's QFET looks interesting.  SiC type MOSFET would be excellent choice, but have not been able to find them.

Use a sequence circuit of three or more mosfets driven by transistors - will post later today.  This will create a train of pulses.

On the 7mhz multivibrator - increase voltage to 3v or even 5v.  At 1.5v output is very small - like 1v.  Transistors are 2N5449.  I pulled that circuit off the web, but now have the book that it came from.  This circuit will work at over 10mhz !  Can be used to drive mosfets or transistors, etc.

What is your pulse width at the control coil?  Does it have a drop at the end?