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Author Topic: Power transformer question  (Read 2956 times)
W2EAF
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Posts: 19




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« on: July 01, 2012, 03:51:32 PM »

My apologies in advance for asking what might seem to be an elementary question, but if a power transformer secondary is rated at 600V-0-600V, is that the same as 1200V ct, or is it 600V ct? I've never been clear on this. Huh
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KA5N
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« Reply #1 on: July 01, 2012, 03:57:20 PM »

Same as 1200 volts CT. Of course you would insulate the CT wire if you used the full 1200 volts You can also use it as two 600 volt supplies with a common
ground (and appropriate rectifiers, caps etc.)

ALLen KA5N
« Last Edit: July 01, 2012, 04:00:00 PM by KA5N » Logged
AC5UP
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« Reply #2 on: July 01, 2012, 05:18:08 PM »

...and with a pair of bridge rectifier blocks you could have a differential supply of +600 VDC / -600 VDC.

A center tap opens up many possibilities. If you haven't seen this, you should:  http://www.hammondmfg.com/pdf/5c007.pdf

The ripple filter & rectifier selection does affect the current capability of a power supply.
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W2EAF
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« Reply #3 on: July 02, 2012, 10:02:38 PM »

Thanks for clearing that up for me, guys! I'll be using a choke input filter, BTW.
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K4FMX
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« Reply #4 on: July 06, 2012, 07:22:58 PM »

My apologies in advance for asking what might seem to be an elementary question, but if a power transformer secondary is rated at 600V-0-600V, is that the same as 1200V ct, or is it 600V ct? I've never been clear on this. Huh

Generally it is not the same rating as 1200v ct.
600-0-600 volt designates that the transformer is designed for use with a full wave rectifier with center tap at ground.
A 1200 vct designated transformer while esentially the same transformer, may be rated the same or it may be rated for use with a bridge rectifier.

some, particularly older, 600-0-600 volt transformers may not have insulation to withstand the center tap being above ground.

A transformer that is rated for a full wave rectifier will often have a different current rating than one rated for a bridge rectifier.

73
Gary K4FMX
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W2EAF
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« Reply #5 on: July 07, 2012, 10:16:03 AM »

It will use a full wave rectifier with the center tap grounded. Actually the circuit is from the RCA receiving tube manual, for the 50W hi fi audio amp. It is especially interesting in that it uses an 0A2 regulator tube and a 6GF7 for electronic voltage regulation. For the stereo version, it calls for the power transformer to be 600V-0-600V at 300ma, with a Freed DC6A recommended. No luck on finding the specs for that one! I know the filament current ratings would have to be higher than the 6.3v @5A and 5V@3A of the transformer specified for the mono version (a Thordarson 22R36), since it will be supplying twice as many tubes. I'm trying to decide which Hammond model will work, and it's getting a bit more complicated than I expected. But hey, that's half the fun, right? Grin
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AC5UP
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« Reply #6 on: July 07, 2012, 12:28:59 PM »

This may call for a visit to:      THE BUNKER OF DOOM !       http://www.bunkerofdoom.com/xfm/

...where you can find the answer to almost any question. In a left-handed way. Sorta'.

Poke around long enough and you'll find a link to the AudioPhool site, then stumble across the TechoPhool page:   http://www.audiophool.cjb.net/Techno.html   which I think you'll find amusing, and a link to this dude...    http://www.audiophool.cjb.net/Misc/53_freed.djvu    Portions of the Freed transformer catalog from 1953.

Note: My Deja' Vu browser plug-in choked on this file. Download it to your desktop then open it with the standalone DJVU viewer.

On page N-75 you'll discover the Freed DC6A was not a specific transformer, but the case outline and mounting spec for their "15 Pound" transformer offerings. Translation: There were multiple flavors of the Freed DC6A transformer and (at least in 1953) none of them show as 600-0-600 VAC. For that you needed to jump to their DC-7BL transformer outline. (?) Don't be afraid to poke around either site as your efforts will be rewarded by a virtual plethora of schematics and construction tips for 50's vintage DIY Hi-Fi Amplificators.

Assuming that's the sort of thing you might be interested in............................... 

BTW: This is what hard-core home audio looks like:   http://www.jogis-roehrenbude.de/Leserbriefe/Drehko-Stefan-6C33C-Amp/Stefan-6C33-Amp.htm

N4NYY tells me he's built monoblock amplifiers nicer than this, but unfortunately they were all in his dreams......................    Roll Eyes
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