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Post subject: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 5:20 am
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Most of our vintage amps were designed with 110VAC in mind.

Now that outlet voltage is 120VAC or more doesnt it make sense to use a step down transformer? Not only does it prevent these old amps from overheating, supposedly they may sound better at lower voltage.

Has anyone tried using a step-down transformer for Japan since it can step down from 120 to 100? Yes, its not 110 but I figure 100 should be fine and may even sound "browner"?

BTW...I have a 1955 Bassman which Ive heard doesnt really have too much of a problem using the higher 120 voltage compared to say a Deluxe.

What are your thoughts on this?

Kurt


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 5:57 am
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I bought a volatge reducer for my amps that will take it down 6 or 12 VAC from whatever the line voltage is...in my case it stays around 125 volts.
I'm at work and don't have the link but I'll post it later,maybe I can find it here,we're blocked from a lot of sites.
Yes,my amps do seem to run cooler and they sound different...better really.


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 5:59 am
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Like I thought I'm blocked from the site here at work,but here's a review of the box from Premier Guitar magazine.
http://www.premierguitar.com/Magazine/I ... eview.aspx

devices like this can be made...I've seen a schematic for it somewhere...I just went ahead and bought this one.


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 6:31 am
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Thanks for that link!

I was looking ALL over for something like this and was thinking somebody HAD
to be making such a device.

They are going for $160 now with a 2 - 3 week wait.

Still not sure if I should get one of those or try a Powerbright VC500J step down transformer for $29.99 Would there be any detriment to using voltage at 100VAC?


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 8:38 am
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You can use a fews 10 volts 5 watts zener diodes in series with the center tap of your power transformer.

Those diodes step down voltage in the amp like the amp is designed when wall outlet had 110 volts.

But this mean open amp and do some electronic/ soldering work.........

Zener are $0.75 each + terminal $3 and work ( $ ? )


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 9:01 am
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stratele52 wrote:
You can use a fews 10 volts 5 watts zener diodes in series with the center tap of your power transformer.

Those diodes step down voltage in the amp like the amp is designed when wall outlet had 110 volts.

But this mean open amp and do some electronic/ soldering work.........

Zener are $0.75 each + terminal $3 and work ( $ ? )


+1

However, Leo (to his credit) was adamant about over-building his trannies so today's higher input voltages to the PT are probably less of an issue than is commonly believed (at least as far as the health and safe operation of the amp is concerned). Whether Triad, Woodward-Schumacher, or Better Coil & Transformer, all of this iron is so over-spec that the 8% to 10% over-voltage is easily tolerated. That said, in the case of the older tweeds and browns, their trannies (like all of the components) are aging. Thus, Stratele's mod suggestions merit consideration as worthy alternatives to a stand-alone step-down device.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 10:59 am
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+ 1 Retroverbial

I have few vintages amp and I don't modify them. They use 125 vac from my wall outlet, no zener.


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 11:07 am
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L' egal icí, mon amí.

But I'd give some serious thought to a step-down tranny if I owned, say, an all-original 1949 Dual Professional or an early K&F Model 26. They're just too precious to put at risk.

Rawk on, Stratele!

8)

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 12:16 pm
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Arjay, I know what you mean. I run my 1948 Champion through a 15-amp Superior Variac. Just so I can tweak the voltage back to 115VAC. It works well, as long as you don't have "little hands" that like to twirl knobs. 8^)

I actually have three Variacs. One that is set to 115 VAC. And I remove the knob.


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Post subject: Re: Step down transformer for JAPAN
Posted: Tue Sep 13, 2011 2:31 pm
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A '48 Champ definitely merits extraordinary precautions!

8)

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Step down transformer for JAPAN
Posted: Wed Sep 14, 2011 10:11 am
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First post....
A 15-20% over voltage on the mains may not be detrimental to the high voltage section, depending on the condition and rating of the capacitors but the operating point, and plate impedance will change so expect a difference in sound, particularly harmonic content.
A minor over voltage condition is hardest on heaters however. They are designed for a narrow range of voltage, so a higher voltage will increase emission....for a while but greatly shorten the life of the tubes. Less difference in life will be seen with the low current heater tubes....12AX7's etc but expect 30% or more reduction in power tube life.
Given all the variables that contribute to tone and feel of an amp, introducing one more that impacts so many characteristics of the amp does not sound like it is worth tempting fate with either the sound or reliability.
There used to be ballast reducers available, maybe an old neighborhood TV shop might still have one from when line stability was important.
A Sola constant voltage transformer could be found in surplus or industrial junk stores that would make line voltage a non-issue. Someone mentioned the Variac, good choice is it is metered but do not risk your amp on an un-metered Variac. The difference between 100 and 130 is not easily determined by the dial markings. eBay has lots of $9 digital LCD panel meters for AC that would turn a $15 bare frame variac into a useful tool for a musician or tech.
I You can use a bucking /boost coil, an inductor that goes in series with the primary to increase or decrease the effective voltage through the primary. That would work but you would need to check whether the line level where you were playing needed it, and have a way to bypass it if you didn't.
A Zener would work on the B+ but leaves the heaters over stressed, not advised.
Good luck


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Post subject: Re: Step down transformer for JAPAN
Posted: Wed Sep 14, 2011 6:46 pm
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Informative first post km6xz...welcome,...what kind of work do you do?....do you own vintage amps?
Sounds like you have some experience with electronics. :D


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Post subject: Re: Step down transformer for JAPAN
Posted: Wed Sep 14, 2011 7:06 pm
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Here's a link to a nice Variac with built-in digital readout:

http://variac.com/staco_3PN10_20.htm


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