Mysterious Resonant Circuit

[aleks]

I second what Peterae said,  the transistor is critical.   I think it's that high hfe constant, which for me it's 200.

Sounds like "arm" effect. The higher the HFE the higher will be the current on collector given base's current. Probably can be replaced by more turns on base's winding. I.e. for HFE=50 use 4*8=32 turns instead of 8. Just a speculation. Well, I'm probably mistaken here - this should be 8/4=2 turns (i.e. lower voltage at base -> higher current at base -> higher current at collector). Or maybe I'm completely off here. Sorry for confusion - just posting an idea.

[Yucca]

@Yucca,

Your waveforms are very close to what I got, as is your amperage.  Get rid of that iron powder core!

Yep the core was from a PC PSU, it was the mains filter. I have a big roll (5kg of 25mm width) of metglass tape on the way from canada woohoo primarily for working on Thane's bitoroid. But I will make a little toroid up for blocking oscillator research too.

[Yucca]

RE my waveform:
I've just discovered tonight that the waveform I posted was only a small part of the overall waveform, I'm embarrassed to admit  but I never zoomed out by turning down the timebase, I guess it's because I was lucky to have the timebase set to 10ns and it just happened to catch the 32mhz nicely.

Anyway when I zoomed out I saw that I was getting pulses running at about 10khz, each pulse had a few hundred oscillations in it at 32mhz. This explains the DVM giving me a lower current reading than the scope on the input, the scope was only catching the higher amplitude 32mhz pulses with its trigger.

Each pulse had an exponential decay envelope to it that fell about halfway and then stepped sharply to zero, I was suprised to see such a complex waveform from such a simple circuit. I will experiment more with this 2N3904 variant of the circuit.

[duff]

I have not been able to replicate EM's results yet though I have wound numerious toroids with the cores I have available. Today I purchased 2n4401 transistors, as EM used, and was still not able to get results so I can assume that the core material is the component I am missing. I have order more cores from Amidon so hopefully they will be here early next week.

I have had some rather interesting wave forms develope that I thought I would share. I got these today after installing the 2n4401 in the circuit. The other transistors that I tried with the same circuit did not produce these results.

Here's a list of the transistors I tried that did not work

mps8099 hfe=267
2n2222a hfe=195 (cross match for 2n4401)
bc547   hfe=363
2n3904, hfe=272
2n3440, hfe=53
2n3439  hfe=207

The octagonal ring came from an old 20" Gateway monitor that someone threw away and I tried it as a last resort being that I gotten no results with my other toriods.

The ring has all kinds of possiblilities for managing rotation

Duff

[pauldude000]

I don't know what is going on with my replication (I use the term loosely, as crossreferenced trannies I had for a match would not oscillate at all). Yet, I am going to have to post some shots, as I decided that I may need to vary the pulse frequency, so used a 100k pot. Too low, and a npn goes POOF (I have a small handfull of these. ;d )

I am getting 70volt spikes from hell across the output resistors.

I am going to have to post scope shots, so that you all can make heads or tails of what is happening. I will do it when I get a chance in the near future. One of the few waveforms I have seen not easily explainable by myself in some manner.

Paul Andrulis