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Old 18th September 2010, 09:42 AM   #1
coit is offline coit  Australia
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Default Easy Way To Reduce 251V to 235V?

Can anyone supply an easy way to reduce 251 volt mains voltage to say 235-240 volts?I'm sick of blowing tubes.
I want to build a jukebox with 3 tube and 1 SS amps,and want to reduce the pressure on the tubes.I just want to reduce the mains voltage for all amps.I've thought of using resistors in parallel to achieve the power handling.
What do you think? Custom transformer?
thanks
Paul
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Old 18th September 2010, 09:49 AM   #2
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Quote:
Originally Posted by coit View Post
Can anyone supply an easy way to reduce 251 volt mains voltage to say 235-240 volts?I'm sick of blowing tubes.
I want to build a jukebox with 3 tube and 1 SS amps,and want to reduce the pressure on the tubes.I just want to reduce the mains voltage for all amps.I've thought of using resistors in parallel to achieve the power handling.
What do you think? Custom transformer?
thanks
Paul
bit unclear on what your problem is Paul - is the 251 V AC or DC? Measured where in the circuit? A difference in B+ of 11 to 16 volts is NOT what is blowing tubes...
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Old 18th September 2010, 10:05 AM   #3
coit is offline coit  Australia
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My AC mains voltage from the wall outlet is 251V.This I think is too high for tube amps that usually specify 230V AC input.
I know I could alter each amp that I buy, but I'm looking for a way to reduce the GPO voltage by a small amount without paying heaps.
I hope this makes sense.
thanks
Paul
PS Solid state amps don't seem to mind the extra voltage but I worry about tube amps,especially fixed bias.

Last edited by coit; 18th September 2010 at 10:09 AM.
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Old 18th September 2010, 10:22 AM   #4
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Read this: 240v to 220v
Especially post #7
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Old 21st September 2010, 06:53 AM   #5
coit is offline coit  Australia
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Thankyou for the replies.I read the article on bucking transformers on the ESP site and decided to build one.
When I went to the Tortech transformer site to look for an appropriate tranny; lo and behold they have introduced a pair of autotransformers to knock 20V off your power supply.Serendipity.
thanks
Paul
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