Cheap power iron at the e-place (the ten pounders)

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Cheap power iron at the e-place (the ten pounders)

Postby EWBrown » Sat Oct 16, 2010 5:38 pm

These may be of interest to the DIYers out there, and they're cheap enough to use as doorstops, too ;) (lol)

I found some rather interesting power trannies, for cheap, on the e-place, these are fairly hefty 120Watt rated power trannies, with 235VAC, 44VAC, and three 6.3VAC filament windings. Designed to be used with a voltage doubler for around 600VDC B+, or with a bridge for around 300VDC. Price, a princely $20 each. Made by Woodward-Schumacher in Chicago. I couldn't resist, went for two, the shipping is $11.70 for the two.

http://cgi.ebay.com/NOS-POWER-TRANSFORM ... 4aa4785cd2

THIS AUCTION IS FOR A NEW OLD STOCK TRANSFORMER FOR A TUBE POWER-AMP. PROJECT. IT HAS A COPPER FLUX SHORTING BAND. DUAL PRIMARY. IT'S SECONDARY VOLTAGES ARE, RED to RED 235v NO CENTER TAP---BLUE to BLUE 44v --- GREEN to GREEN 6.8v with C.T.and THICKER WIRE ---YELLOW to YELLOW 6.8v ---ORANGE to ORANGE 6.8v. ALL VOLT VALUES UNLOADED. Not knowing the specs on this transformer. I proceeded as follows.

I loaded the secondary red winding to 200 ma. and filament green winding to 6 A. The voltages are now 607 VDC and 6.3 VAC., for 8 hours to check for temperature rise. I did not load the YELLOW or ORANGE winding thinking they are for tube rectifier filaments which probably no one will use, and BLUE is only for negative bias. I had a 35 degree C rise in primary temperature..DIMENSIONS ARE 3 1/2 x 4 7/8 x 4 1/4 HIGH


Image

He also has another version with a 170VAC HV winding, which can double for 440VDC or bridge for 220VDC. Good for those big 6EM7 / 6GF7A designs, this beast could easily run 8 of them... (666) or 8 to 12 6BM8s =:o

I think the postal delivery woman is gonna be cussing about when this heavy package arrives. >:o :'( :( Couple of ten pound chunks of USDA prime grade "pig iron" in a flat rate box... I'll file them under the Herniator and Gut Buster categories =:o ;) (lol)

/ed B
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Postby kheper » Sat Oct 16, 2010 6:05 pm

"I loaded the secondary red winding to 200 ma"

Ed - do you know what the max current out for the red to red winding is?

At that price, they would be nice for some monobocks - if the max current was not sufficient for a PP UL stereo amp.
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Postby Ty_Bower » Sat Oct 16, 2010 6:14 pm

I've got one of each (#7018 and #7019). I'm using the lower voltage version (170V) for my 6BM8 project. Massive overkill, but the price was right.

The primaries on these things must have been wound for 110V or something, as all the secondaries seem to run high. The 6.3 volt windings were quite a bit higher than spec as I recall. I'm going to use one of the 6.3 volt windings in series with the primary to make it a bit longer, which ought to bring everything else back into line.

I've got some photos of the beast in the "Low Watts" thread, if you want to see what it looks like next to an Edcor GXSE5.
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Postby EWBrown » Sat Oct 16, 2010 6:31 pm

Ed - do you know what the max current out for the red to red winding is?

At that price, they would be nice for some monobocks - if the max current was not sufficient for a PP UL stereo amp.


IIRC, in a voltage doubler, the AC input current to the doubler is about 2.8X to 3.6X the DC output current, so we're probably talking around 560-700 mA AC capability on the "red to red" winding. When I get mine, I'll load it up with 2, 3 and 4 40W / 230VAC lightbulbs, and see just how much current it can deliver. With a bridge, it should be good for up to 200 mA @ 330VDC, which could be interesting to use with a PPP EL84 design, or a 4-EL84s paralleled per chanel SE-UL design. I have worked up this particular combination about a year ago, and it could be a real beast, 4 parallel EL84s into a Hammond 1627SE (2.5K) would be good for over 8WPC in triode mode, and about 12WPC in SE-UL mode. These power trannies look like they could handle the DC power requirements.

The No Load "red winding" voltage is 235 VAC, and 6.8VAC for each of the filament windings, which seems to be about the right value right for unloaded AC winding voltage outputs, which are typically 5 to 10% above the nominally loaded operating voltage.. I would SWAG that the 235VAC would drop to around 220VAC under a full current load. If anything these could serve as an isolating step-up / step down trannie, with its two primaries. The filament windings then would jsut be a "bonus" ;) (lol)

Test Results:

Two 115 (120) VAC primaries:

Primary 1: Red/Black (line) and black (neutral)
Primary 2: Red/Green (line) and Yellow/Black (neutral)

For 120VAC, connect Red/Black to Red/Green (line) ; and Black to Yellow/Black (neutral)

For 240VAC: Connect Black to Red/Green; Use Red/Black for Line, and Yellow/Black for Neutral

230VAC, (850 mA) secondary: Red and Red: no-load voltage: 235VAC, fully loaded: 228VAC.

Bias: (44VAC) Blue and Blue - note: Low current

6.3VAC, 5A Filament #1: Green and Green, CT Yellow / Green
6.3VAC, 2A Filament #2: Yellow and Yellow.
6.3VAC, 2A Filament #3: Orange and Orange

These two windings can be connected in parallel for 6.3VAC @ 4A, or in series for 12.6VAC, 2A. There are no "phasing" markings,
so there is a 50/50 chance of getting either the "right" connection :)) , or the "wrong" connection :'( .

I tested it with the 230VAC and 6.3VAC windings fully loaded: 228 VAC @850 mA on the 230VAC winding, loaded to 850 mA (2 100 watt, 120V light bulbs connected in series). Line voltage was 120VAC.

For Full wave bridge, divide 850 mA by 1.8; For a voltage doubler, Divide 850 by 3.6. This is the "conservative" rating method.

For a full wave bridge, max DC loading would be 472 mA continuous. For a voltage doubler, the max DC loading would be 236 mA, continuous..

6.3VAC, 5A winding loaded with four 6AV5GA filaments (1.2 A each) connected in parallel, for 4.8 Amps loading.

No loading on the two 6.3VAC 2A windings O:) I let it run for many hours, the transformer got warm, but not hot to the touch.

This thing is a BEAST!


FWIW the seller is located in Pennsylvania.

/ed B
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Postby Geek » Sat Oct 16, 2010 8:20 pm

Whatta deal!

I bet it's a regulated PSU transformer... the other 6.3V windings for the floating heaters on the pass regulator and error amp.

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Postby kheper » Sat Oct 16, 2010 11:19 pm

EWBrown wrote:With a bridge, it should be good for up to 200 mA @ 330VDC, which could be interesting to use with a PPP EL84 design, or a 4-EL84s paralleled per chanel SE-UL design. I have worked up this particular combination about a year ago, and it could be a real beast, 4 parallel EL84s into a Hammond 1627SE (2.5K) would be good for over 8WPC in triode mode, and about 12WPC in SE-UL mode. These power trannies look like they could handle the DC power requirements.

FWIW the seller is located in Pennsylvania.

/ed B


Thanks Ed.

Ty_Bower wrote:The primaries on these things must have been wound for 110V or something, as all the secondaries seem to run high."


As a FWB, I'll bet it'll push 350V. A sweet spot for SE 807s.
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Postby burnedfingers » Sun Oct 17, 2010 4:45 am

I bought two of them. ;)
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Postby Ty_Bower » Sun Oct 17, 2010 7:42 am

kheper wrote:
Ty_Bower wrote:The primaries on these things must have been wound for 110V or something, as all the secondaries seem to run high."


As a FWB, I'll bet it'll push 350V. A sweet spot for SE 807s.


No, the voltages quoted by the seller are the voltages he measured on his own wall voltage. He didn't say what it was, but I was guessing just slightly under 120. The voltages he advertises should be pretty close to what you get.

My concern was mainly with the heater winding. If the transformer was designed to deliver 6.3V with a 110V supply, it's going to be over 7.1 when I plug it into my 125V wall outlets.
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Postby kheper » Sun Oct 17, 2010 9:46 am

Ty_Bower wrote:
kheper wrote:
Ty_Bower wrote:The primaries on these things must have been wound for 110V or something, as all the secondaries seem to run high."


As a FWB, I'll bet it'll push 350V. A sweet spot for SE 807s.


No, the voltages quoted by the seller are the voltages he measured on his own wall voltage. He didn't say what it was, but I was guessing just slightly under 120. The voltages he advertises should be pretty close to what you get.


Correct. Duh on my part.
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Postby EWBrown » Sun Oct 17, 2010 12:15 pm

I'd SWAG that the primaries are 115VAC, and from the photos, no 110/115/120 taps on them, not enough wires... These were definitely produced in the "SS voltage doubler" era, which would place them in the late 60s / early 70s vintage. The separate bias "blue"winding is another clue of their age. The traditional tapped HV secondary winding technique doesn't work with doublers.

About five years ago this, or another e-bay seller was unloading 60 Watt PP Schumacher 4.3K:4/8 open-frame OPTs for dirt cheap, and he had massive quantities of them, so back then, I bought tow of them. He also sold them in "bulk" quantities, Cheaper by the box-load, too...

The "extra" filament windings would be good for feeding SRPP or VA/CF filaments, where they have to be "floated" at a voltage halfway between the two cathode voltages.

I figured they're cheap enough, that they were worth a gander, so I got two of the "235V" units. Two power trannies, in search of suitable projects ;) (lol)

/ed B
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Postby Geek » Sun Oct 17, 2010 3:44 pm

Why does cross border shipping have to be so expensive! Image

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disgruntled ?

Postby EWBrown » Mon Oct 18, 2010 1:24 pm

Those Disgruntled Posties gotta make a living, c'om.... ;) After all ammunition costs a lot of money these days :/ $) >:o :'(

Just received a package from Mayne Island BC, weight about 13 lbs / 6 KG, and the postage was almost $33 . Which was included in the purchase price (appx $195 total). Took about ten days total, so there must be sufficent snow for the dog sled teams to run ;) (lol) :))


Could be that the "North America's Future Thrown Away" act has something to do with it (???) $) (???) $) :/

/ed B
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Postby lth1 » Mon Oct 18, 2010 2:24 pm

Since some of the people with knowledge on the forum are purchasing these Xfmrs I decided to get 2 each.

I did not know you could parallel the HV secondary with the 6.3V windings, if that is the case can the 33 and 44 volt windings be added to the 170 and 235 to produce no load voltages of 203 and 279?

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Postby EWBrown » Mon Oct 18, 2010 2:30 pm

The 6.3VAC filament windings can be paralleled with each other, as long as the voltages are the same. They CANNOT be paralleled with the HV and bias windings. They could be connected in series, see below.

The 33 /44VAC winding is most likely rated at a fairly low current, on the order of 25 mA or less, as grid biasing requirements generally do not draw much current, except for that dissipated in the resistive voltage dividers and potentiometers. It would not ot a good idea to connect in series with the 170/236VAC HV sindings, which have much higher current capabilities.

The "extra" filament windingas could be series connected with the HV winding if you needed 6 or 12VAC above the HV winding's AC voltage.

Or just use them separately, connected in series, to feed 12VAC filament tubes.

/ed B
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Postby Ty_Bower » Tue Oct 19, 2010 8:08 am

Ty_Bower wrote:The primaries on these things must have been wound for 110V or something, as all the secondaries seem to run high. The 6.3 volt windings were quite a bit higher than spec as I recall.


I found the notes I took for #7018.

Primary winding: 123 VAC (my line voltage), 1.5 ohms DC resistance
High voltage secondary: 176.2 VAC, 2.9 ohms DC resistance
Blue winding: 34.5 VAC
Green winding: 7.01 VAC (with center tap)
Yellow winding: 7.01 VAC (no center tap)
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