Compatible Transistors

[Fraulein]

Hello! I have been running my 5 filars coil with the 2N3055. I am thinking of building a multi coils- multi filars upgrade to my device. However I can not find any of the usual transistors at my supplier. They do not carry the MJL21194, or the BU2508AF, or the FJL6020 , or the 2SC5588....

This is very bad for me....I guess. However they do carry some POWER transistor NPN. They have in stock;

BU426 6A 800V
BU208A Fast switching 8A 700V
BU508A Fast switching 5A 700 V
2N6404 16A 600V

Will any of these will make for satisfactory alternative? I am still learning a lot about electronics and my learning curve is very steep indeed.

[cindi]

Hi tom
How do we see with one transistor is compatible with the other?
By measuring the values base to emiter and base to collector having the same value?

[James Milner]

Tom,
1st of all I can say that used to run my bifilar SG without a neon. And unhooked from the secondary to test the peak discharge voltage via a cap across the collector and emitter without blowing it up! It was 12V and tuned to low current at the time. Although this was not great on the 2N3055's, and I blew more than my fair share! It was ok on the MJL21194's
2nd I have had a battery short while I wasn't looking (was at work actually), burn all the neons and come to a complete stop, also burning out the 22 Ohm resistor on my 5 filar #18 SG. (thats what you get using useless batteries!). And all 4 transistors were ok!
So I think that empirically proves your assertion on post #12.

What intrigues me as a very novice electronics person, is the tuning John B does to bring his amplifiers to class A. If John spends so much time tuning the amplifiers so carefully and then states that the SG is even more critical.
Is beta matching really enough?
I have beta matched transistors, matched resistors within .1 Ohm and diodes matched to 3 decimal places. Can I go further to improve outcomes?

I do notice without the secondary battery hooked up the neons do not fire all in unison, (I only do a momentary burst as I find the neons heat up and crack due to shock cooling) which to me suggests minor variations in the timing of the transistors opening and closing the current to the primary.
Can you elaborate on say tuning each transistors base current and switching voltage, or am I trying to be too cute? It would obviously be better if the longtitudinal pulse is perfectly timed across all four (or more) transistors.
Maybe this subject deserves a thread of its own?
Thanks
James

[Tom C]

Tom,
1st of all I can say that used to run my bifilar SG without a neon. And unhooked from the secondary to test the peak discharge voltage via a cap across the collector and emitter without blowing it up! It was 12V and tuned to low current at the time. Although this was not great on the 2N3055's, and I blew more than my fair share! It was ok on the MJL21194's
2nd I have had a battery short while I wasn't looking (was at work actually), burn all the neons and come to a complete stop, also burning out the 22 Ohm resistor on my 5 filar #18 SG. (thats what you get using useless batteries!). And all 4 transistors were ok!
So I think that empirically proves your assertion on post #12.

What intrigues me as a very novice electronics person, is the tuning John B does to bring his amplifiers to class A. If John spends so much time tuning the amplifiers so carefully and then states that the SG is even more critical.
Is beta matching really enough?
I have beta matched transistors, matched resistors within .1 Ohm and diodes matched to 3 decimal places. Can I go further to improve outcomes?

I do notice without the secondary battery hooked up the neons do not fire all in unison, (I only do a momentary burst as I find the neons heat up and crack due to shock cooling) which to me suggests minor variations in the timing of the transistors opening and closing the current to the primary.
Can you elaborate on say tuning each transistors base current and switching voltage, or am I trying to be too cute? It would obviously be better if the longtitudinal pulse is perfectly timed across all four (or more) transistors.
Maybe this subject deserves a thread of its own?
Thanks
James

anything you can do to help bring your system into resonance do it. match coils, their inductance, just think about it, some of the things are minuscule and may or may not bring improvement.

Tom C

[James Milner]

Thanks Tom,
Yep done the coils too. All exactly 130ft long all at exactly 1.1 Ohms a strand.
I'm trying to think what else I can do. As I'm not an old hand at electronics,but learning, can you pass on any experience or observations from John B as to how to improve resonance that may not be any of the above mentioned items however small?
Thanks
James

[Tom C]

Thanks Tom,
Yep done the coils too. All exactly 130ft long all at exactly 1.1 Ohms a strand.
I'm trying to think what else I can do. As I'm not an old hand at electronics,but learning, can you pass on any experience or observations from John B as to how to improve resonance that may not be any of the above mentioned items however small?
Thanks
James

no I cannot
Tom C

[Tom C]

Hi tom
How do we see with one transistor is compatible with the other?
By measuring the values base to emiter and base to collector having the same value?

you can use the HFe on your multi meter. it will give you a number. use that number to match transistors.
Tom

[fathershand]

Tom, a vendor offers matched transistors with this statement: "Units are considered "matched" with Vbe +/- 2% and hfe +/-5%". Is this acceptable for our work? Also, some vendors make transistors with high HFE numbers, but the transistors don't work right. How can we avoid this? I was thinking of buying NTE transistors and components. What is your opinion of NTE? The NTE replacement for MJL21194 is NTE2670.

Thanks
Tony

[Tom C]

Tom, a vendor offers matched transistors with this statement: "Units are considered "matched" with Vbe +/- 2% and hfe +/-5%". Is this acceptable for our work? Also, some vendors make transistors with high HFE numbers, but the transistors don't work right. How can we avoid this? I was thinking of buying NTE transistors and components. What is your opinion of NTE? The NTE replacement for MJL21194 is NTE2670.

Thanks
Tony

yes that is fine for the tolerance. NTE has their own numbering system, its the same exact transistor.
Tom C

[Tom C]

Thanks Tom,
Yep done the coils too. All exactly 130ft long all at exactly 1.1 Ohms a strand.
I'm trying to think what else I can do. As I'm not an old hand at electronics,but learning, can you pass on any experience or observations from John B as to how to improve resonance that may not be any of the above mentioned items however small?
Thanks
James

however small......... none of this is from JB, ok here goes:

magnets exact spacing and gauss
transistor matched EXACTLY not within 5 percent you need an expensive machine for this
inductance on each coil matched with an inductance meter not just resistance, yes it is different....
use 1 percent resistors and match them, they will run better as they change temp.
rotor perfectly balanced and the less friction of any type you have the better be
big wire to and from your charge batteries
drive the primary with a solar panel and a big capactior in parallel instead of a battery you are at cop of infinity once the panel is paid for

how can you make the machine better. look at every component individually.. make it better. make the mechanical better, wind your coils slower and tigher, litz your wires carefully it goes on and on and on. its like building a race car, at some point they are looking for performance increases down in the 10th of a percent.

Tom C

[James Milner]

Thanks Tom,
Great stuff!
The more I look at the detail, the more I'm convinced engineering becomes artwork. Just look at natural biological systems.

James

[Tom C]

Thanks Tom,
Great stuff!
The more I look at the detail, the more I'm convinced engineering becomes artwork. Just look at natural biological systems.

James

I agree science and art merge at some point in time and the creative process becomes the driving force for advancement in technology.
Tom C

[Dave Wing]

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Dave Wing

[Dave Wing]

Also, some vendors make transistors with high HFE numbers, but the transistors don't work right. How can we avoid this?

Hi Tony,

To combat this problem only buy name brand transistors from a reputable supplier, it may be a higher cost but at least you know what you are getting for the money. Some factories produce fake transistors that give you a high HFE but will not pass anywhere near the current they are supposed to, all they do is heat up when in use at low current levels and will not function properly in your circuit. Which is problematic for the end user, such as yourself and others. A YouTube user posted this video which may give some important insight to this fake transistor problem... FAKE 2SC1969 & 2SC2312 HFE & OUTPUT TEST. - YouTube

Hope this helps.

Dave Wing

[fathershand]

Thanks, Dave. I saw that video and that's one reason I made the post. You said "reputable supplier", can anyone on here give the names of these? I am considering buying NTE electronics because I think that they are genuine quality parts. What is your take on this?

Thanks
Tony