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Old 8th December 2012, 02:07 AM   #41
bear is offline bear
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The DCR != (is not equal to) the output Z.

You want to determine the voltage ratio first, then plug it into the formula and get the actual impedance ratio.

Likely with all the secondaries together you have more like 16ohms or 32 ohms.

It's unclear to me if you said there are two primaries - each pair of tubes go to their own windings - OR if the tubes are in push-pull parallel. That would be two tubes going to a single winding, and then the other two tubes go to the other end of the winding, with a CT in the middle.

It seems you are a bit confused about things like "magnetization". It's not a factor.

There should be no DC offset between each side of the tubes, if properly biased and balanced.

Oh yes, the different DCR of the halves of the secondaries. Usually this will happen if one half the secondary is wound close to the center of the windings, and the other outside. It's the same number of turns, but the turns on the outside are longer than the ones on the inside, so the DCR is different.

There are ways to overcome this, but not all output transformers are built to do this.

Use a small AC source, like a an AC wall supply (12vac, 10vac, 5vac, etc) to provide a signal to use for determining the turns ratio. Use a DVM and calculator and you can figure out the ratio, and knowing the target plate Z for the tubes, know the output Z...

http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]
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Old 12th December 2012, 10:54 AM   #42
sulfamate is offline sulfamate
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Join Date: Nov 2012
Thanks for the reply
PP two valves in each side of the CT primary
I am having fun so far deciphering them
Any input is well received
Will not be around for a few weeks traveling overseas
Project has come to a standstill at this point in time
Back into it as soon as I get back
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