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Author Topic: Dally, Shark & Ruslan workbench  (Read 114613 times)

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...and the Kacher output (probe laying next to coil)
This might allow us to determine the phase of the base oscillations relative to the Kacher output.
Won't the placement of the probe affect that phase ?
I am asking in case the electric field does not propagate infinitely quickly along the Kacher coils.
   

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  PW:
  The suggestion to use a trim pot instead of the R17 has not been taken seriously. I think that that is the real solution to the transistor not kicking on issue.

   Verpies:  Concerning the idea of the Kacher antenna feed back to pulse components on the drivers. As I've said, I doubt that is the case.
Burning them, yes. Yet, you may be right.
   However, Geofusion has shown that moving his yoke closes or further away from the grenade coils, did seam to change his output.
But, mine does not act like in the same manner.

   Vasik: There are some things that I don't understand, as I don't understand Russian.
   The idea of pulsing the kacher base circuit by the TL494 makes me wonder, if both the Kacher as well as the induction circuits will then be running at the SAME frequency? Or how then is the Kacher running frequency controlled?
   

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Won't the placement of the probe affect that phase ?
I am asking in case the electric field does not propagate infinitely quickly along the Kacher coils.


   Verpies: I can't answer that, but, I can say that once the Kacher is also running along with the induction circuit, any negative scope ground probe will affect the readings, and should not be used. As it will short out the HV to ground. At that point, I just use the positive scope probe, without negative one connected. Not the best way, but it works for me.
   
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Vasik,

Does your Kacher still oscillate if you disconnect the antenna input to the base of Q6?

PW
   

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In your "oscillating" scope shot, what voltage were you using?

PW,

Yesterdays pictures were taken with 14v, today's with 50v

Vasik


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   

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Nick,

   Vasik: There are some things that I don't understand, as I don't understand Russian.
   The idea of pulsing the kacher base circuit by the TL494 makes me wonder, if both the Kacher as well as the induction circuits will then be running at the SAME frequency? Or how then is the Kacher running frequency controlled?

kacher give pulse bursts, these bursts synchronized with LC (TL494)
Isn't it clear from schematic ?

Vasik


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   

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Does your Kacher still oscillate if you disconnect the antenna input to the base of Q6?

No, it does not.


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   
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Vasik,

Thank-you for your replies.

PW
   
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No, it does not.

Vasik,

Will your circuit at least ring-down similar to Itsu's with the antenna disconnected?

PW
   

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OK, i have made R17 variable (100K trimmer plus 1K parallel to the 8.2K) and adjusted it to 3.3K

Now again at 12V collector voltage (140mA) i have strong oscillations and RF showing on the near by yellow probe and a NE-2 neon.
Red probe is on the base which now has superimposed strong HF oscillations which makes measurements problematic.

Itsu
   

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Buy me a cigar
What is Wimbledon?

A world famous lawn tennis tournament.   ;)


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Nanny state ? Left at the gate !! :)
   

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Here the base (red) and pin7 of the IR2113 (yellow).

   

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PW,

Will your circuit at least ring-down similar to Itsu's with the antenna disconnected?

If you mean these oscillations (marked red) they will be there even if I remove Q6 (but I haven't tried disconnecting secondary coil).
These oscillations caused by Q4, Q5 switching.

Vasik


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   

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OK, i have made R17 variable (100K trimmer plus 1K parallel to the 8.2K) and adjusted it to 3.3K

Now again at 12V collector voltage (140mA) i have strong oscillations and RF showing on the near by yellow probe and a NE-2 neon.
Red probe is on the base which now has superimposed strong HF oscillations which makes measurements problematic.


Looks good  O0


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   

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Yes, i thought so.

Swapping the kachers primary coil leads stops the oscillations so they are good as they are now, also when increasing R17 to about 6K, the oscillations (12V on collector) stops.

Itsu
   

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Doing some experiments using a Gas Discharge Tube (GDT) of 350V at the end of the antenna to ground to see if that causes the typical kacher signal as shown in Vasik his post #1055 above.


Seems this GDT is to slow as it looks like that only "every other" gated kacher oscillation cycle is cut off.

Red is base, yellow probe near by antenna.

Itsu
   

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Here an expanded view of the base signal (red) and collector signal (yellow) to show the phase relations.
Seems to me the signals at the start of the base signal are 180° out of phase.

Itsu
   

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Seems to me the signals at the start of the base signal are 180° out of phase.
The common-emitter amplifier is an inverting amplifier.
   

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Right, so they stimulate each other (oscillate)
   

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While keeping 200mA through the transistor, a collector voltage of 45V and R17 set at 5K is the max. 
After that, increasing the voltage will increase the current above 200mA, but also getting bigger amplitude pulses on the base.

Itsu
   

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Right, so they stimulate each other (oscillate)
...and changing the delay around the loop*, affects this oscillation.
Also, flipping the coil around changes the phase shift of the entire loop from 180° to 0° and the self-excitation stops entirely.
Breaking the loop or decreasing the loop's gain stops the self-excitation, too.

* The loop consists of the amplifier (BJT) with its feedback path (coil/antenna).  The delay of this loop is most reliably measured with a single short pulse between the collector and the antenna (disconnected).
« Last Edit: 2021-06-21, 10:29:42 by verpies »
   

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While keeping 200mA through the transistor, a collector voltage of 45V and R17 set at 5K is the max. 
After that, increasing the voltage will increase the current above 200mA, but also getting bigger amplitude pulses on the base.

Itsu


    Looking good Itsu, your best scope shot yet.

    NickZ
   
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While keeping 200mA through the transistor, a collector voltage of 45V and R17 set at 5K is the max. 
After that, increasing the voltage will increase the current above 200mA, but also getting bigger amplitude pulses on the base.

Itsu

Itsu,

Be aware that if the "200ma through the transistor" you mention is your collector current as measured during DC bias conditions, that 200ma will have little meaning under dynamic conditions.

While operating at 45 volts, the base is seeing voltages (spikes) that approach 3.5v.  Whether that base voltage is "real" or an artifact moreso related to ground or lead inductance needs to be determined.  However, if the base is indeed being driven to ca 3.5v, that infers very high base peak currents.  As well, the absolute maximum for Vbe is 5v.  It is likely that adjusting the 45v collector supply much higher will start putting those base excursions very close to that limit.

Q6 is saturating so depending on the load impedance, Ic could be approaching a very significant portion of the maximum allowable collector current.

When probing Vbe and Vce, attach your scope probe ground lead directly on the emitter or as close to it as possible. 

Perhaps discussions should shift toward possible ways to measure Ib and Ic under dynamic conditions with minimal effect on circuit operation.

How fast are your current probes?


PW



   
   

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Be aware that if the "200ma through the transistor" you mention is your collector current as measured during DC bias conditions, that 200ma will have little meaning under dynamic conditions.
Yes, the 200mA during DC bias conditions, does not mean a 200mA amplitude of current flowing through the primary coil.

I agree with everything PW wrote above.

@PW
Since Q6 is recommended for audio amplifier applications, I wonder whether its base-emitter parasitic capacitance (Cπ) and Drain-Source capacitance (CDS) of the Q4 are large enough to limit base currents at the high frequencies arriving from the coil/antenna.
   
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Again, the Vbe of a bipolar power transistor such as the 2SC5200 can in no way reach 5v or anything close.  The actual max Vbe encountered should be ~1.5v at the maximum collector current.  In Itsu's scope shots of the base voltage is not an accurate measurement of the actual base voltage IMO.

To accurately measure the Vbe, simply place one probe at the emitter and another probe at the base where these leads exit the device and measure the differential.  This eliminates all lead inductances.

Regards,
Pm
   
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