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Old 13th November 2003, 05:45 AM   #1
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Default C core output transformer

Helo everyone,

I would like to try and make my own c core output transformers. Can anybody help with the winding setup schema and connection set up?

Thank you very much.

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Old 13th November 2003, 08:25 AM   #2
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Only info I could find on the net.

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Old 15th November 2003, 01:53 PM   #3
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Hello GlassPainter ...

Could you please tell us what kind of amp you have in mind ??
SE / PP . perhaps other .. Also what tubes / bias point / plate impedance etc.

A friend of me did some expiriments with big C core OPT's
( handwinded ) few years ago .. I believe he still has sleepless nights ;-) .. I could ask him for some specific explanation

Happy Ears

BTW : IsraŽl .. nice country .. I spend some time in Rehovot .
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Old 15th November 2003, 02:23 PM   #4
tiroth is offline tiroth  United States
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When you do layered windings like that, do you wind them on only one side of the core? The C-core mains transformers I've seen all had seperated windings, one on each side.
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Old 15th November 2003, 04:55 PM   #5
tvi is offline tvi  Australia
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The following might be of interest:

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Old 15th November 2003, 09:13 PM   #6
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Some theory:


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Old 16th November 2003, 07:12 AM   #7
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Default C core outpots

Hello Happy ears,

I am working in Rehovot so I know the area well, talk about an ever shrinking world...

Anyway, I would like to build a single C core output for ECL82 about 200v on the plate 25 ma idle current and about 15v bias.

I have built several ECL82 amps and ended up using a Japan maid EI transformer for very good performance (it is used mainly for my Grado headphones), and dcided to try C core as well.

All the info I was able to gather on the net was very poor and all of it was EI oriented, if I understand correctly the calculations for EI are not accurate for C core, plus the C core uses a dubble bobbin setup which changes the wiring diagram.

Thanks for the info so far everyone.

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Old 16th November 2003, 11:51 PM   #8
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Smile C-core

Hi GlassPainter ,

The ECL82 AFAIK needs 7K primairy .. still a lot of windings to turn .. hell of a job man .. but with patience .............
Do you have some equipment to get this job done ? I mean .. this seems rather ridiculous to get done just by hand ?

Another idea is to look out for some original datasheets of the Philips C-core OPT's .. I know Philips manufactured great sounding C-core outputs back in the 60's & 70's.. also for ECL82 SE use . ( V30 stereo amp , 2 x 3 watt SE )
Also HF309 monoblocks still are desireable because their PP/UL EL84 C-core OPT's

If you wish I could try to figure out the production numbers of those "old days" beauties , and who knows Philips Librairy can provide details about winding #'s etc.
Mostly Philips didn't make a huge secret about their winding technique .. many Philips amp circuits I'v seen from the books show OPT layout .. like core size , winding numbers etc.

Happy Ears

PS: Altough it's been 18 years ago , I can still remember Rehovot quite well .. I stay at Teler street near the busstation/market place . Also the restaurant at Bilou junction where I often eat shakshouka and humus with harissa ..
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Old 25th December 2005, 09:21 AM   #9
bigbulb is offline bigbulb  Canada
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I'm searching for Philips c core info too, without luck. Here's a page regarding small c core trans and also philips V30 trans clone.

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