How can I turn 120VAC to 100VAC for Tango MS-UVD in an 845 SE amp? - diyAudio
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Old 20th December 2010, 08:46 PM   #1
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Default How can I turn 120VAC to 100VAC for Tango MS-UVD in an 845 SE amp?

I have an 845 SE amp with the Tango MS-UVD Power Transformer. The primary is 100V. Could someone tell me how I can bring down 120VAC to 100V? Could I use a resistor and perhaps with a capacitor?
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Old 20th December 2010, 08:49 PM   #2
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How to wire a 'Buck' transformer

The principles are all there. If you need more specifics, let me know.
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Old 20th December 2010, 09:02 PM   #3
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Also here: Bucking Xfmrs
If I understand correctly you'll need a xformer with a 20V secondary. Primary and secondary winding are then wired in series (Fig4) and used as a voltage divider.
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Last edited by Rodeodave; 20th December 2010 at 09:05 PM.
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Old 20th December 2010, 09:54 PM   #4
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Thank you guys for the information.

It seems like the best way to reduce the voltage is by using a buck transformer.

Do I need to buy a separate transformer or do I use the secondary voltage of the Tango power transformer that is in my amplifier?
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Old 20th December 2010, 09:58 PM   #5
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Here is a picture of the Tango power transformer.
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Old 20th December 2010, 09:59 PM   #6
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Old 20th December 2010, 10:33 PM   #7
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I see that I would need a separate transformer.

My main voltage is 124V. Seems like I would need a transformer with 24V secondary. What about the primary voltage?

Could you guys tell me where I can get a good transformer?
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Old 20th December 2010, 10:50 PM   #8
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Quote:
Originally Posted by manp111 View Post
I see that I would need a separate transformer.

My main voltage is 124V. Seems like I would need a transformer with 24V secondary. What about the primary voltage?

Could you guys tell me where I can get a good transformer?

Current transformers intended for the U.S. market generally have 120V primaries, no real choice here. Anything in the 20V - 24V range is going to work fine.. You haven't mentioned what the current consumption of this amplifier is on 100V - that is a part of the puzzle that is missing, and I usually like to chose a transformer that is rated at twice the maximum current I will use it at for this sort of application.

Antek makes toroids that are pretty good for this application for very reasonable money.. Digikey, Mouser and Allied Electronics also sell a variety of transformers that would be well suited for this application.
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Old 20th December 2010, 10:56 PM   #9
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I haven't measure the current of this amp. I need to replace the fuse on my meter. The amp is an 845 SE so I suspect that it draws about 300w or 3 amps.
I will measure the current when I get the fuse. Assume that it draws 3 amps, what is the current of the transformer I should get?

Last edited by HP8903B; 20th December 2010 at 10:59 PM.
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Old 20th December 2010, 11:16 PM   #10
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Apex Jr. has a 160va toriod with dual 24v secondaries. If you wire the
secondarys in parrallel that should be good for 24v at 6.6A. By the way
just for YOU in keeping with the holliday sperit. I have a small isolation transformer case that would probably be neet to wire the bucking transformer up in. Free for the shipping.

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