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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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7th May 2007, 7:38 am | #61 | |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: Toroids as O/P trannies
Quote:
the 60KHz seems strange to me. Maybe it is caused by the 10pF in the base circuit. But since big toroid mains transformers work well in pp amps, (GU50, PL5XY) I think yours with much more windings will do it much better, I wish. Good luck, Darius PS: Let us see some pics of the rewinding, thanks. |
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7th May 2007, 5:45 pm | #62 |
Pentode
Join Date: Jun 2006
Location: Malaga, Spain.
Posts: 235
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Re: Toroids as O/P trannies
Hi Old Europe and all,
Made a mistake in the calcs, haven't used a hand calculator in yrs. I ran it on an online calculator a few minutes ago and with 22pF the res freq would be only 5KHz, at 60KHz the capacitance would have to be 0.15pF, an impossible figure. At 28Hz with 0.69uF the 45H is correct. I have looked at specs on O/P transformers and the primary inductance ranges from 10H upwards to even 100H. From the calcs with 1H and 22pF resonance is at 33KHz and I don't think anyone would think of using a transformer with 1H inductance. Something here is not correct!!! The oscillator circuit I used drew about 2mA so that should not have caused any changes in inductance. What did you think was strange with the 60KHz resonant frequency? Mike |
9th May 2007, 10:26 am | #63 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: Toroids as O/P trannies
Hi, I am no expert but I am pretty sure the winding capacitance occurs throughout the winding and therefore willl not contribute to resonance.
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9th May 2007, 6:17 pm | #64 |
Pentode
Join Date: Jun 2006
Location: Malaga, Spain.
Posts: 235
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Re: Toroids as O/P trannies
Hi PJL, the capacitance is between each turn and each layer of turns/windings etc, this will result in a very complex series and parallel capacitance arrangement and will have a bearing on the resonant frequency of the transformer. In this case there are some strange effects at play which I don't understand and don't make much sense either when professional transformers specs are consulted.
Mike. |
10th May 2007, 8:34 am | #65 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: Toroids as O/P trannies
Thanks Mike, therefore I am not too sure what you are measuring when you allow the open primary to resonate? Just the in circuit capacitance?
Not sure if you found this supplier http://www.amplimo.nl/index.html?lan...arget=d21.html but there are some detailed specs which might help confirm your design. |
11th May 2007, 9:38 pm | #66 |
Hexode
Join Date: Feb 2006
Location: Diss, Norfolk, UK.
Posts: 386
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Re: Toroids as O/P trannies
Hi
You might find this site. www.amplimo.nl/ interesting it is a Dutch company which makes toriod O/P transformers. Trevor |
23rd May 2007, 11:19 am | #67 |
Pentode
Join Date: Jun 2006
Location: Malaga, Spain.
Posts: 235
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Re: Toroids as O/P trannies
OK thanks, will take a look, can't do anything much at the moment as I'm in the Middle East for 12 weeks.
Mike. |