100 volt input on PT

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danman
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100 volt input on PT

Post by danman » Thu Sep 19, 2013 11:27 pm

Hello everyone, I am starting a new build on a JMP 50 watt (68 lead spec) and I am trying to decide on which PT I should get. I notice that on some of the PT's listed for this model have an extra 100 volt primary tap along with the standard 120/220/240 inputs. What is the purpose of this? Is this simply for areas that have 100 volt service (which I didnt know existed) or can you use this tap with a variac to achieve a lower voltage on the secondary? I have been searching for several days now and can not seem to find an answer so I thought I would check with you guys first before making a purchase. Thanks for any info you can provide on this.

danman
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Re: 100 volt input on PT

Post by danman » Sat Sep 21, 2013 5:24 pm

I finally found my answer on the Classictone site today. It turns out that the 100volt winding is for use in Japan. Guess I wouldn't need that option!

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Re: 100 volt input on PT

Post by rockgod212 » Sun Mar 29, 2015 2:20 pm

but does the 100volt tap lower the plate voltage at all compared to 120volt, I have the same transformer and I just got a variac and I want to lower it. right now im at 436vdc unbiased@120vac, so will the 100volt tap variaced to 100vac input lower the plate voltage, or will it still be the same as the 120vac input?
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Brian Wallace
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Re: 100 volt input on PT

Post by Brian Wallace » Sat Apr 04, 2015 12:32 pm

Using the 100VAC primary tap with the US 120VAC wall voltage will raise all the secondary voltages.
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syscokid
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Re: 100 volt input on PT

Post by syscokid » Sat Apr 04, 2015 4:49 pm

Can any part of the amp get damaged if you use the 220vac tap with an actual 120vac supply?
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Re: 100 volt input on PT

Post by Haze13 » Sat Apr 04, 2015 11:06 pm

If there is enough voltage for the heaters than probably not. Every thing just will be lower... B+, bias, heaters...
ADA preamps run this way. ~4vdc for heaters and less than 200 volts for B+.

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