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Bucking transformer?

larryderouin

larryderouin

I'm VERTICAL and Breathing...most of the time.
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So I need what to bring my FISHER 400 down to a reasonable voltage from 124. a 120/10V 3-4amp transformer? Then take the one secondary(hot side) and wire it to the primary so the secondary is in series with the primary? and leave the Neutral to go thru straight? Kinda like a Dim Bulb Tester?

Ratshack should have something like that, right? The drawings I saw on 'net thru google intimated that but I'm not real comfortable just doing it.

This is how I understand it.

Say the transformer has 4 leads. 1 and 2 are primary. 3 and 4 are secondary.
Wire the Hot line from wall to 1. Tie 2 and 3 together, and 4 goes to hot side of line to unit. Neutral goes straight thru? Is this correct? But if I tie 2 and 4 together I raise the voltage. So i check voltage from trans 1st before hooking up receiver.

Use a bat if necessary to get it in to my thick skull, please.

Thanks
Larry
 
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One of these days I'm gonna make an isolation x-former with a few windings removed from the secondary, that should solve the problem.
 
Im glad this came up. This has been in the works for me for a couple years.

Ive got a 1930's guitar amp that likes 105v so I only play it thru a variac.

Kinda cool though because the variac acts like an effects box. At 100v the amp sounds brown and silky. At 123v (my wall voltage) it sounds stingy and actualy compresses the sound to where it burps out of the speaker
Cool but not worth ruining a vintage historical piece.

One of these is gonna fit the bill soon.
 
I made mine using a RS 12.6v TX with center tap. Wired it in a box and added a regular wall outlet. One socket is -12.6v and the other is -6.3v ( or close enough). Perfect for my vintage gear while my wall voltage is often 124vAC.
 
Damn. I just now finished mine, and hooked it up. Double gang box and single box. Transformer (R.S. 12V with CT). Broke off the center tab between the plugs on the hot side and hooked up the same way. One -12.6 and other -6.3. Actually easier than I thought it would be. used a 12ft extension cord with polarized plug cut the end off and cut off what I needed for internal wiring. Soldered, wirenuts and e-tape. I don't want any shorts caused by loose wiring.

While i was out getting the stuff for it, I thought about just mounting the tx on the chassis, but thought about it for a few seconds and said NaaaaaaHHHHHHHHH.

Running it on the -12.6v tap (108.6vac) and it doesn't sound so strained. It's more open.

Larry.
 
If you have some stuff in your junkbox, dig through that before buying a purpose transformer. I've made use of otherwise worthless transformers out of a UPS and a boom box for bucking transformers.
 
No junk box. But I'll keep the idea in mind.

Ran it all day y'day and this morning. It's opened up even more. Sound stage has improved, it's like the speakers have melted into the walls (kind of hard to describe), and it just fills the room better.

Now with the FISHER Consoles I can make them built in as part of the console.

Larry
 
larryderouin said:
Damn. I just now finished mine, and hooked it up.--snip--
Click to expand...

Well? Is it still working? I've been kicking around doing the same thing for some time now. Also, debating whether or not to shell out for a Sencore 57. Then, saw this guy built his own from a step-down transformer: http://www.youtube.com/user/Lockemeister#p/u/7/5kfQyqPJ7Mk (skip ahead to 7:00 to see how he proposed to make a bucking transformer setup).

Then I read your post and, I think I'll do it your way. So, I'm looking on the Radio Shack website and found what looks like the same transformer. So, I'm reading the reviews on it and there are 3 or 4 reviews that the buyers say the first transformer burned out and they're on their second ones.

So, just wondering how's yours is holding up. I may run down to RS here in a minute. I'm used to taking things back...
 
I built one last year, using a NOS Triad 6.3v/4a filament transformer.
I installed it into a two gang outlet box, along with a dual Leviton output.
This drops my line voltage down 6.3 volts, to the approx. 117 vac that my 50's and 60's vintage gear like to see.
It has gotten a LOT of use, and is holding up fine.

Steve
 
Blast said:
So, just wondering how's yours is holding up. I may run down to RS here in a minute. I'm used to taking things back...
Click to expand...

My Radio Shack bucking transformer has been pulling routine duty on my large Grundig console for well over a year. No issues at all so far.
 
I looked all over yesterday and came up with nada.

All my local Shacks that even carry transformers only have the 12v up to 3a and I have my heart set on a 4a model for my my old amp.

Big retailer Fry's only carry's seemingly unusable voltage combinations and even my favorite independant had a bin for them but it was empty. :tears:

All of those places would have had it for around $12 or so IF they stocked it.

I ended up Ordering a Hammond from Mouser for around $30 shipped. I know it sounds snobbish but even though I could have ordered it from Radio Shack, I dont want a transformer under the chassis of my badass old amp that has "Radio Shack" stamped into the frame. The picture of the Hammond transformer "looks" to be of a better quality than the RS ones.

Cant wait to do this though. :yes:

..
 
I must be doing something wrong. No matter which legs I use my DMM says the same line voltage as at the wall.

If, when hooked up to a table lamp, I get either nothing, or about 4 volts going to the table lamp.

Maybe it won't power a lamp, only a transformer. Maybe I should just go ahead and try it on the amplifier.
 
Nevermind... It works...

DOH! :boring:

I'm using the CT and dropping to 113V on my 222C. I'm going to see if the PT doesn't get so hot now.
 
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I don't know. After a few hours last night at 113vac I STILL couldn't keep my hand on it... It seems like I got a lot more mileage last week by putting a slow running fan (12vdc fan running at about 4vdc) on the PT.

I'm going to try the 12.6v drop to 106vac tonight.

Then, I'm going to bring my IR thermometer home from work and do an "in-depth study" this weekend. :nerd: I'll post the results.
 
I'm running mine on 107V. The Pwr Trannie get lukewarm. And the heat from the output tubes is a lot less than it was before. Even the wife noticed it sounds better now when she had a Count Basie tape on today.

Guess I'll have to make a few more, for the consoles and the Sansui 1000A.
 
I asked on another thread ( http://www.audiokarma.org/forums/showpost.php?p=3662735&postcount=19 ) but I feel I'm at the right place here...

So, I built a bucking tranny but used 120v/12v with center tap 2 amperes.

I'm wondering if 2A is sufficient. What do you think?

It's for an Eico HF-81. It has fuse rating of 250v@2A so it's why I thought that would be enough.

The transformer doesn't look to get hot BTW...

Looking here, the guy recommend 2 or 3A: http://www.geofex.com/article_folders/vintvolt/vintvolt.htm.

I don't want to fry anything...

**There's only the Eico on the bucking transfo, the AC acessory outlet is long gone.

I don't know if my maths are correct:

On the back of the Eico:

- power consumption: 140w
- line voltage: 116.5

So 140w divided by 116.5 = 1.2A

Correct or not?

Thanks.

Patrice
 
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