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2x18VAC instead of 18-0-18
2x18VAC instead of 18-0-18
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Old 31st May 2011, 07:36 PM   #1
Hubba is offline Hubba  Sweden
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Default 2x18VAC instead of 18-0-18


I have difficulty to source a 18-0-18 500VA transformer for a dual polarity PSU. Could someone confirm that I can use a 2x18VAC 500VA and connect the secondaries in series, and thus creating a center tap where the two secondaries are joined...

kind of like: 2x18 VAC ---> 18-0-18

Thank you,
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Old 31st May 2011, 07:42 PM   #2
infinia is offline infinia  United States
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yes you could do that , but better ripple performance to build a dual full wave rectified / filtered supply and join them at the outputs. You will have less one extra diode drop for each side.
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Old 31st May 2011, 07:43 PM   #3
sofaspud is offline sofaspud  United States
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You can use a dual secondary tranny as a center tap. Just make sure you connect them in phase.
Is a 36VCT that difficult to find?
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
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Old 31st May 2011, 07:52 PM   #4
Hubba is offline Hubba  Sweden
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Thanks for the replies...

I'll start with the 2x18 and test the circuit, and put the 18-0-18 on the list of future updates.

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Old 6th June 2011, 12:06 AM   #5
nigelwright7557 is offline nigelwright7557  United Kingdom
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If the transformer has say two red and two white wires on the secondaries then connect a red to a white for a center tap.
PCBCAD51 pcb design software. 2018 version out now with lower prices >> http://www.murtonpikesystems.co.uk
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Old 9th June 2011, 01:09 PM   #6
deltaunit is offline deltaunit  United States
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I've just posted a similar question in the parts forum.

When a 2x 18v is wired in series for centre tapped output like above, is the output 36v?
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Old 10th June 2011, 09:28 AM   #7
AndrewT is offline AndrewT  Scotland
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use a mains bulb tester for every power up !!!!!!!!!!!!!!!
regards Andrew T.
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