Author Topic: Modifying transformer voltage  (Read 573 times)

Offline DACMan1

Re: Modifying transformer voltage
« Reply #15 on: May 22, 2020, 04:45:43 PM »
No, meneer. No stripping. You already have access to the primary connections. All you do is add, say, 20 turns. Connect it in series with your primary. Measure the difference in output. If it goes lower, change the polarity of your new coil. See by how much it boosts the output voltage. This should give you an idea of how many turns you should have in total to achieve your target. This works; I have done it in my own amplifier. The advantage is that, as it is a primary, you don't need thick wire (only as thick as the existing primary). Be sure to insulate sufficiently.

I would not advocate messing with the primary.

Offline Shonver

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Re: Modifying transformer voltage
« Reply #16 on: May 22, 2020, 04:49:12 PM »
I would not advocate messing with the primary.

Your objection?
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Offline Baine Bloodhoof

Re: Modifying transformer voltage
« Reply #17 on: May 22, 2020, 06:37:01 PM »
I too would like to know what the neg is on messing with the primary.
“Perhaps I am inclined to prejudge, I think better of the tauren than I do of orcs.”

Offline Timber_MG

Re: Modifying transformer voltage
« Reply #18 on: May 22, 2020, 06:41:02 PM »
I too would like to know what the neg is on messing with the primary.

You can very easily saturate the core and have a real mess on your hands. If you add windings you will increase losses slightly but taking them off is a recipe for disaster.

Offline Baine Bloodhoof

Re: Modifying transformer voltage
« Reply #19 on: May 22, 2020, 06:58:29 PM »
Shonver talking about adding windings on the primary. I need about 5 volts more on the secondary side. I was thinking of a few windings in series with the secondary windings, just enough to give me roughly 17 volts ac. Or does my thinking only work if its one continuous winding with various taps along it. Kinda like separate batteries in series  :help:
“Perhaps I am inclined to prejudge, I think better of the tauren than I do of orcs.”

Offline Timber_MG

Re: Modifying transformer voltage
« Reply #20 on: May 22, 2020, 07:50:08 PM »
Shonver talking about adding windings on the primary. I need about 5 volts more on the secondary side. I was thinking of a few windings in series with the secondary windings, just enough to give me roughly 17 volts ac. Or does my thinking only work if its one continuous winding with various taps along it. Kinda like separate batteries in series  :help:

As long as the ternary winding is in the same magnetic field and has sufficient wire diameter for the amperage there is nothing stopping you. It's not fire code and w.h.y. but for DIY it might work in a pinch.

Offline Shonver

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Re: Modifying transformer voltage
« Reply #21 on: May 22, 2020, 07:51:15 PM »
If you are adding windings to the secondary then you will have to double it up. One for each branch.
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Offline Baine Bloodhoof

Re: Modifying transformer voltage
« Reply #22 on: May 22, 2020, 08:16:41 PM »
wire is 1m thick, and yes, will double up, one for each secondary.
“Perhaps I am inclined to prejudge, I think better of the tauren than I do of orcs.”

Offline Baine Bloodhoof

Re: Modifying transformer voltage
« Reply #23 on: May 22, 2020, 08:21:21 PM »
I saw a design here that allowed a transformer with  dual Ac outs to be converted to a dual rail psu. So like in my case, a 0-12-0-12 to a 12-0-12. I would assume that it is just a matter of connecting two of the sec output wires together and using that as the ground or 0 volt rail, and then the remaining two wires will be + and - vcc?
“Perhaps I am inclined to prejudge, I think better of the tauren than I do of orcs.”

Offline Shonver

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Re: Modifying transformer voltage
« Reply #24 on: May 22, 2020, 09:29:13 PM »
You can make the connection and verify it with a meter.

Connect it like this:

You have a 12-0 (A) and another 12-0 (B). Connect (A)'s 0 to (B)'s 12. This will be your centre tap. The two unconnected wires (or terminals) will be the 12s of the new 12-0-12. Measuring across the two 12s should give you 24V. If you get 0V, one of the 12-0 windings must be reversed.
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Offline Shonver

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Re: Modifying transformer voltage
« Reply #25 on: May 22, 2020, 09:33:14 PM »
To get the (+)-(0)-(-) DC conversion, connect your bridge rectifier across the 12s. The centre tap will be your 0V.
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Offline fredeb

Re: Modifying transformer voltage
« Reply #26 on: May 22, 2020, 09:34:54 PM »
I saw a design here that allowed a transformer with  dual Ac outs to be converted to a dual rail psu. So like in my case, a 0-12-0-12 to a 12-0-12. I would assume that it is just a matter of connecting two of the sec output wires together and using that as the ground or 0 volt rail, and then the remaining two wires will be + and - vcc?

Exactly what Shonver says ...

Yes , that is right . Connect it up to mains and you might be pleasantly surprised that the primary was configured for 220V  and you have 13-0-13 or 14-0-14 .

Another idea , that @Ampdog suggested to me to step down the voltage of a transformer can also be used to  boost the voltage , for this you need another transformer in front of the torroidal boosting the primary voltage  .
See here : https://sound-au.com/articles/buck-xfmr.htm#s40

... and here : https://www.avforums.co.za/index.php/topic,61508.msg761807.html#msg761807


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Offline Shonver

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Re: Modifying transformer voltage
« Reply #27 on: May 22, 2020, 09:36:13 PM »
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Offline Baine Bloodhoof

Re: Modifying transformer voltage
« Reply #28 on: May 22, 2020, 10:05:48 PM »
You can make the connection and verify it with a meter.

Connect it like this:

You have a 12-0 (A) and another 12-0 (B). Connect (A)'s 0 to (B)'s 12. This will be your centre tap. The two unconnected wires (or terminals) will be the 12s of the new 12-0-12. Measuring across the two 12s should give you 24V. If you get 0V, one of the 12-0 windings must be reversed.

Thank you for that sir, much appreciated.
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Offline Hi-Phibian

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Re: Modifying transformer voltage
« Reply #29 on: May 23, 2020, 07:43:55 AM »
Still think it’s a clunky way with a nice toroid.  Settle for a bit less voltage swing.  I believe the current capacity of the amplifier will be the same. The transformer will not be optimal when modified imo. 


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