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Hoffman Amps Forum image Author Topic: Univox U-45B bad OT  (Read 2812 times)

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Offline jeff

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Univox U-45B bad OT
« on: August 23, 2010, 02:12:07 pm »
I have a univox U-45B with a bad OT. The original OT was 16K.
I can't find one that's 16K but I do have an extra 8K OT lying around.
Is it ok to use the 8K and then run the 4Ω tap to a 8Ω speaker?
What are the drawbacks of doing this?

Offline Geezer

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Re: Univox U-45B bad OT
« Reply #1 on: August 23, 2010, 02:38:35 pm »
Yes, that will work.......8k/4Ω becomes 16k/8Ω with an 8Ω speaker applied.

Drawbacks? None, but what is the relative size comparison of the 2x OT's? If they are ~~the same physical size, they should perform about the same. If the new OT is slightly larger, you may get a better low end response, or vice-versa if it is slightly smaller than the original.
Will probably work just fine or better, either way......

Geezer
« Last Edit: August 23, 2010, 02:41:03 pm by Geezer »
   Cunfuze-us say: "He who say "It can't be done" should stay out of way of him who doing it!"

Offline PRR

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Re: Univox U-45B bad OT
« Reply #2 on: August 24, 2010, 01:05:51 am »
Plate supply voltage should be similar for similar bass-overload.

This suggests up-watting the nominal size. You would get back down to stock size by winding with a smaller gauge, but this is not an (easy) option.

Plate supply voltage is ~~280V. The world is full of 8K OTs for 6V6 at 280V-350V. Any of these will be fine (loaded 8r on the "4r" tap) if it fits.

 


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