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Old 23rd July 2011, 04:12 PM   #1
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Default unused secondaries on SE opt?

I have searched the threads but have not found a definitive answer for my situation. A question for those more experienced; I am building again a 6BQ5 SE and using some SE opt's from a tubed Sony reel-to-reel, they are 5K with 8 ohm and 600 ohm secondaries. I have in the past just left the 600 ohm sec. floating and taped them off and grounded the black common from the 8 ohm sec. Would I benefit from terminating the unused 600 ohm sec. across a 600 ohm resistor? I don't have any test equipment anymore so I cannot test the freq. response of the transformer. TIA for the advice.
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Old 23rd July 2011, 04:40 PM   #2
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You should not terminate the unused secondary.
Terminating the 600 ohm winding will reduce the amount of available power on the 8 ohm winding and will reduce the primary impedance because the transformer is double-terminated.
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Old 23rd July 2011, 05:12 PM   #3
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So I should just tape them off and not worry about it then. Thanks for the reply.
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Old 23rd July 2011, 07:12 PM   #4
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I had the same problem: a NOS Stancor OPT that included two "tertiary" windings for whatever reason (cathode feedback, perhaps?) that I wasn't going to use. In that case, I taped 'em off, making sure that the ends were of unequal length, and tied down along with the rest of the leads. Just make sure the unused secondary(ies) won't accidentally short circuit, and you're good to go.
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