Dr Ronald Stiffler SEC technology

[gyulasun]

... 
  The battery input voltages are 4v, 8v, or 12v. But, the transistor is getting hot on any of those voltages. ...   

Hi Nick,

Well, I forgot to comment what you wrote above. It is true that the (2S)C1815 has a very wide range for its hFE specification, it is selected into groups. The hFE can be any value from 70 to 140 for the O suffix, 120 to 240 for the Y suffix, 200 to 400 for GR suffix and 350 to 700 for BL suffix. You can see these suffixes marked on the case and it is possible you happen to have a type with very high hFE value (if everything else is ok, that is) and the 100 kOhm base resistor may be increased to set a lower transistor current.  So let's pick a 'worst case' example when hFE is say 700 and supply voltage is 12V. If you use the 100 kOhm base resistor (which is in parallel with the crystal) then the base current is 0.12mA and the DC collector current then 700 x 0.12mA = 84mA. From a 4V supply, the base current is 0.04mA and the collector current would be then 28mA. This latter collector current can already warm up (but not so hot) the transistor from 4V and surely make it hot from 8 and especially from a 12V supply.

The solution is to use a 1 MegaOhm trimmer potmeter instead of the fix 100 kOhm, even a 470 kOhm in series with the 100 kOhm can reduce the transistor heat.
Please measure the DC current taken from 12V to learn about the actual current which flows into the oscillator when the 100 kOhm base resistor is used. IT is very good you reduced the supply voltage to 4V to see how warm or hot the transistor in that case.  From 4V, it cannot be as hot as from 8 or 12V though. 

Can you see a sinewave-like waveform on the collector versus the negative rail?

Gyula

[NickZ]

   Gyula:   Here are some scope shots of my oscillator running on a 3.5MHz and a 7.2Mhz crystal. Scope probes are on the collector/emitter.  Even though I have shortened my L3 coil, it does not do as well using a 13.5MHz crystal, as with the two crystals mentioned above.   
  And now it stopped working, so I need to look into that, again.  This is a very touchy circuit, no doubt about that.
  I will try to add some more resistance, to see if I can lower the transistor heating at 8 and 12v. 
  I don't have any high voltage near field wireless effects, as yet. Are there supposed to be wireless effects at this voltage???

[gyulasun]

Hi Nick,

Very nice progress, thanks.  You have unusually high voltage amplitudes across the collector and emitter (264 Vpp or 222 Vpp), what is the supply voltage you used when took the snapshots?  Maybe a 10 times division is missing at the probe or on the scope vertical amplitude settings?   26.4 Vpp or 22.2 Vpp would sound more realistic.  The shape of the waveform is ok for an untuned collector choke without resonance.
Do you have the same choke coil in the collector you showed earlier in a photo of your oscillator with the power transistor?

You wrote:   "I don't have any high voltage near field wireless effects, as yet.  Are there supposed to be wireless effects at this voltage???"

Well, if you have the choke coil in the collector you had showed, then it has a ferrite core too if I recall correctly so that most of the field is confined in and close to the body of the ferrite choke. This may greatly reduce 'wireless effects'. 
A coil like the L3 has bigger mechanical sizes and no ferromagnetic core to collect and confine the field, so much more 'wireless effect' can manifest in its vicinity.  A normal AV plug with a white LED may give some brightness though when you touch the common diode input as single wire of the AV plug to the collector.

Hopefully your transistor did not get cooked by the heat developed in it.  What is the input current? you could use a DC ampermeter simply in series with one of the input supply rails.
Gyula

[Lidmotor]

All--  I found two good transistors for the Crystal oscillator circuit that can handle higher power and thus produce more light using higher voltage.  These are the two:  MJE181 and BD243C.  I did not seek these out but had them on hand and just tried them.  Both can handle up to 30 volts input into the crystal circuit.  They get warm at that voltage but a simple heat sink is all you need.   The little booster power supply gizmo (like Slider is using also) trips out if the amperage gets too much and with these two transistors it keep right on going at 30 volts. 

Nick---  You are right about the 13.5MHz crystal circuit being touchy. The L3 coil being the most critical component I have found.  This is the best coil for my build:  It is a paper tube wrapped with about 90 turns of 26ga wire.  I used a AA battery as the diameter form.  The coil is roughly 5/8"dia x 3 1/8" long.  It has about 2 ohms resistance and is about 100uh.   The fist inductor (choke) is not nearly as critical and I have used ones from 1mh to 3.3mh successfully.  The final lightbulb LED board is another thing that can give you vastly different results as far as real light production.

Gyula---Your help on this project is greatly appreciated.  You fill in the gaps in technical knowledge that some of us have.  I set out to be an EE but never got there.  You give me a glimpse of what the world of true electrical engineering looks like.  Some things you explain I understand and some I don't-----but it all helps.

Slider---Your idea for using a simple EBay voltage booster power supply really helps on this project.  The one I am using has a built in over amperage cutout feature that saves me from causing little transistors to produce that annoying blue smoke. Ha.

All---Slayer (Gary Bluer) came up with a neat little 3 choke exciter that I replicated yesterday. With a few modifications it will run these led 110v lightbulb arrays.  Here is a short video of what it looks like:   https://www.youtube.com/watch?v=xQPpUMIF9T8

[erfandl]

All--  I found two good transistors for the Crystal oscillator circuit that can handle higher power and thus produce more light using higher voltage.  These are the two:  MJE181 and BD243C.  I did not seek these out but had them on hand and just tried them.  Both can handle up to 30 volts input into the crystal circuit.  They get warm at that voltage but a simple heat sink is all you need.   The little booster power supply gizmo (like Slider is using also) trips out if the amperage gets too much and with these two transistors it keep right on going at 30 volts. 

Nick---  You are right about the 13.5MHz crystal circuit being touchy. The L3 coil being the most critical component I have found.  This is the best coil for my build:  It is a paper tube wrapped with about 90 turns of 26ga wire.  I used a AA battery as the diameter form.  The coil is roughly 5/8"dia x 3 1/8" long.  It has about 2 ohms resistance and is about 100uh.   The fist inductor (choke) is not nearly as critical and I have used ones from 1mh to 3.3mh successfully.  The final lightbulb LED board is another thing that can give you vastly different results as far as real light production.

Gyula---Your help on this project is greatly appreciated.  You fill in the gaps in technical knowledge that some of us have.  I set out to be an EE but never got there.  You give me a glimpse of what the world of true electrical engineering looks like.  Some things you explain I understand and some I don't-----but it all helps.

Slider---Your idea for using a simple EBay voltage booster power supply really helps on this project.  The one I am using has a built in over amperage cutout feature that saves me from causing little transistors to produce that annoying blue smoke. Ha.

All---Slayer (Gary Bluer) came up with a neat little 3 choke exciter that I replicated yesterday. With a few modifications it will run these led 110v lightbulb arrays.  Here is a short video of what it looks like:   https://www.youtube.com/watch?v=xQPpUMIF9T8

Hi lidmotor. thanks for sharing. is indutor 1 mega haner ? ( 1000 uh ) ?
thanks