Quad II Output transformer rewinding question - diyAudio
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Old 12th April 2008, 01:09 PM   #1
405man is offline 405man  Scotland
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Default Quad II Output transformer rewinding question

I am in the process of having some Quad II output transformers rewound and have unwound a faulty one and can confirm that the basic arrangement is as shown here

Quad II Mods/Tweeks

and

http://www.diyaudio.com/forums/attac...amp=1139868168

(As mentioned later in the post there is no connection between Z-U or W-X)

The laminations are TU and measure 90X62mm with a 42X22 window. They are alternated with no stacking. There are in effect 14 windings, 8 primary and 6 secondary. Each of the primaries consists of 3 layers of 160 turns and each of the seconderies 1 layer of 51 turns.

I donít have a wire guage to hand but each layer is full, the bobbin is 38mm wide and 160 turns of 34 swg = 0.2337mmX160 = 37.4mm however 51 turns of 24 swg = 0.5588mmX51 = 28.5mm, but 22 swg = 0.7112mmX51 would be 36.3mm which is much closer.

The 3 bottom seconderies are in parallel and the small wirewound device is inserted between the top of the 3rd and 4th windings.

The winding arrangement is p-s-p-s-p-s-p-p-s-p-s-p-s-p. Each of the primary layers as separated by 2 layers of thin paper and the primary and secondary layers are separated by 2 layers of thicker paper. As modern transformers use plastic film between layers how will changing the material affect the transformers performance, is the thickness important and should I have the transformer vacuum impregnated.
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Old 12th April 2008, 01:25 PM   #2
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Default Re: Quad II Output transformer rewinding question

Quote:
Originally posted by 405man
As modern transformers use plastic film between layers how will changing the material affect the transformers performance, is the thickness important and should I have the transformer vacuum impregnated.

Having faced a similar dilemma i decided to use as original materials as possible in order to preserve the "sound" of the transformer. The thickness and type of the insulation will have an effect upon the high frequency response and if matching to another channel is important one should use similar paper. Modern wire is in any case better isolated.

I went for a wax dip and no vacuum and did the job myself.
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Old 12th April 2008, 06:18 PM   #3
EC8010 is offline EC8010  United Kingdom
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Any impregnation will increase capacitance. If it wasn't impregnated before, why impregnate now?
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Old 13th April 2008, 08:23 AM   #4
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Hi 405man,

This was interesting. In the links you refer to the secondaries are 52 turns while you counted to 51.

It would suit one of my future projects fine if your counting is right, .

Or are there different types out there?
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Old 13th April 2008, 09:10 AM   #5
cerrem is offline cerrem  United States
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If your using paper interleaving as the original did, you MUST vacuum impregnate it..... it will probably not last long.....
Kraft paper is not electrically resistant and will burn, unless it is varnish impregnated...
The QUAD II outputs an vary in a turn or two....tolerances were not 100% perfect...

Best Regards
Chris
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Old 13th April 2008, 02:13 PM   #6
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hey-Hey!!!,
Isn't that OPT still available from Quad? or do you suspect it has been changed from the older design?
cheers,
Douglas
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Old 13th April 2008, 07:05 PM   #7
405man is offline 405man  Scotland
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Thanks for the advice, I still have some of the layers to be unwound and I shall check the number of turns again, I have 2 transformers, one from about serial number 18000 and the other about 42000, they look identical.
Though they may still be available from Quad they are very expensive, I had some mains transformers wound at a considerable saving and I have listed the extra ones on eBay from time to time with great success.
I shall be in touch with the transformer manufacturer in the next couple of days to see what insulation material is available, would the main difference be caused by the thickness or the dielectric properties

Stuart
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Old 14th April 2008, 08:06 AM   #8
Serge66 is offline Serge66  Switzerland
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Hi,
A few years ago, I wound a few xformers. I used teflon band to isolate the primary layers plus a layer of thin paper. Teflon is a good insulator with low dielectric coefficient (Er=2). Use the gas type as it is thicker than the water type.

For some time, I had this idea of using synthetic flyscreen to separate the layers. IMO it is ideal, since it is more than 50% air, and the thickness of the plastic wire is about 0.3mm. Mmmmh.
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Old 14th April 2008, 08:21 AM   #9
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405man: How did you separate the transformer from the can?
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Old 17th April 2008, 06:57 PM   #10
405man is offline 405man  Scotland
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Having completed the unwinding of my 2 transformers I have shown the details below
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