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Can I drive a valve circuit with no mains transformer?
Can I drive a valve circuit with no mains transformer?
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Old 1st October 2010, 09:40 AM   #1
leecardan is offline leecardan
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Join Date: Jul 2010
Default Can I drive a valve circuit with no mains transformer?


I'd like to build a circuit that requires 230VDC, or thereabouts
Here in Australia our outlet voltage is 230VAC

Is the use of a 1:1 transformer in this case mandatory or can I simply rectify and filter the mains?

I was going to do something like:

230VAC -> Mains Filter -> Bridge Rectifier -> 400uF / 400V filtering

the mains supply (230VAC) will of course be fused and switched (before the mains filter), the filter I have is:

Click the image to open in full size.
Old 1st October 2010, 11:34 AM   #2
Pano is offline Pano  United States
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Can I drive a valve circuit with no mains transformer?
Please see rule #3 (and note 2) You were supposed to have read those.
Short answer to your question. NO. Not on this forum.

Use a transformer. The life you save may be your own.
Old 1st October 2010, 11:50 AM   #3
metalsculptor is offline metalsculptor  Australia
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Join Date: Sep 2010
Location: Melbourne
The moderators message is wise, the worse shock I ever got was servicing just the type of equipment that you propose, only problem was that active and neutral were swapped in the house wiring I had one hand on earth and the other on B- with a half wave rectified supply. The type of equipment equipment with half wave rectified mains is now banned due to the problems it causes transformers in the supply grid. Full wave rectified mains is even more dangerous and it requires special care to test with B- appearing half wave rectified with respect to neutral making it every bit as dangerous as B+

Use an isolation transformer 240 to 120 V are easy to get then put a half wave voltage doubler on it to get around 300VDC.
Old 1st October 2010, 11:56 AM   #4
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
The early automobile (car) radios were valve (tube). They ran off the battery system.
regards Andrew T.
Old 1st October 2010, 12:40 PM   #5
SY is offline SY  United States
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Location: Chicagoland
Can I drive a valve circuit with no mains transformer?
I generally don't care when people kill themselves doing something insanely dangerous. Problem is when someone innocent gets killed- like a child touching your amp.

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"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

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