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

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Postby DeathRex » Sat Oct 01, 2011 2:36 pm

I got wrote down 235V at 560ma. You can run EL34s at 650V just need to lower the current to 30ma each, and keep the screens below 500V. That would be about 125-135ma for the whole amp, and maybe 55-65 watts in pentode.

A power transformer at 55C would be fine. Once it gets to 70-75 it's getting hot.

Probably should have got the other one he was selling too. It was 170V at 750ma. that would work great on a ST70, making about 450VDC doubling, and easily powering 4 EL34s and 2 preamps.
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Postby burnedfingers » Sun Oct 02, 2011 12:11 am

Posted: Sat Oct 01, 2011 2:36 pm Post subject:

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I got wrote down 235V at 560ma. You can run EL34s at 650V just need to lower the current to 30ma each, and keep the screens below 500V. That would be about 125-135ma for the whole amp, and maybe 55-65 watts in pentode.

A power transformer at 55C would be fine. Once it gets to 70-75 it's getting hot.

Probably should have got the other one he was selling too. It was 170V at 750ma. that would work great on a ST70, making about 450VDC doubling, and easily powering 4 EL34s and 2 preamps.


Your 235v before rectification so around 330vdc rectified. Doubled I think I got 630 or there abouts with 315vdc at the halfway. I will use it and resistor it down to about 485 vdc or so for the plates. It still ought to be good for 280 mA doubled I would guess and should run a stereo amp.

I didn't buy the smaller transformers so I am stuck with what I have.
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Postby burnedfingers » Wed Oct 05, 2011 5:05 am

Did some measurement its a hefty transformer
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Postby DeathRex » Wed Oct 05, 2011 9:54 am

KT88s can take 600 on the screens and 800 on the anode. So your transformer would make about 180-200ma at 630VDC, or 40-45ma each KT88 with 25-27.5 watt plate dissipation. Would be running them kinda easy though. Might be into AB2.
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Postby burnedfingers » Fri Oct 21, 2011 4:22 am

Heater windings in series or use a voltage doubler?

I have some 12volt tubes and would like to use them in a project. I would like to use the transformer I have instead of purchasing a 12 volt transformer to add to the project.
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Postby kheper » Fri Oct 21, 2011 10:55 am

http://www.tubezone.net/pdf/we350b.pdf

The 350b has low max plate and screen voltages, but a 27W plate dissipation. With a FWB and that 560ma supply power, you should get ~335V @ ~350ma, which is suitable for these tubes.

335V x .07A = 23W ; looks about right

There are new production 350b tubes.
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Re: Cheap power iron at the e-place (the ten pounders)

Postby EWBrown » Tue Feb 05, 2013 8:03 pm

The same seller still has the 7018s and another slightly smaller version, on the e-place, now his price is $35 each, 75% higher than the original $20 each :'(

http://www.ebay.com/itm/POWER-TRANSFORM ... 1300662%26

and

http://www.ebay.com/itm/Tube-amp-power- ... 1632143%26

I dragged out one of my 7019s for further testing, and to re-figure out the leads and dual primary connections. No more 7019s available...

/ed B
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Re: Cheap power iron at the e-place (the ten pounders)

Postby burnedfinger » Tue Dec 01, 2015 5:06 pm

Sorry to bring this up again but I purchased 2) of these transformers back when Ed first posted this thread. Check the burnedfingers name (me) I've got a habit of getting back to things right away well at least within 5-10 years. To make a long story short I finally opened up the box again to look at the transformers for a project I want to start on. I believe there was originally a little piece of paper in the box with the primary wiring and its gone. The transformer has the following numbers on it 007019 and right below that is 6066704. Its the big transformer in the first post.

I simply don't know what the wiring is for the primary and would rather not toast the transformer trying to hook it up. If memory is correct it needed to have doubler circuit to obtain a decent operational voltage but then again I'm trying to go on memory.

The primary has the following colors primary side portion of the transformer I mean. Yellow/ green, yellow/blk,red/blk,blk,red/green
The secondary colors are pair of yellow, green,red,blue, and orange.

Any help will be appreciated.
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Re: Cheap power iron at the e-place (the ten pounders)

Postby DeathRex » Wed Dec 02, 2015 9:25 am

I'm building my big amp with that one. For 115VAC the primary wires should have black and black/yellow connected together, and then red/green and black/yellow/red connected together
Red pair = 235@560ma
Green pair = 6.3CT@5A center tap (green/yellow) is with primary wires
Yellow pair = 6.3@2A
Orange pair = 6.3@2A
Blue pair = 44 volts bias

There was also a 170 volt transformer that was sold on ebay, it was a 7018. It was missing the orange pair.

I'm using it seriesed to a 700ma isolation transformer to make 350 volts. I used the 170 volt version as a doubler.
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Re: Cheap power iron at the e-place (the ten pounders)

Postby burnedfingers » Wed Dec 02, 2015 8:08 pm

Thanks for the info.
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Re: Cheap power iron at the e-place (the ten pounders)

Postby EWBrown » Wed Dec 02, 2015 8:50 pm

Back when I received the trannies, I drew up a simple schematic diagram of all of the leads, I'll dig around and see if I still have it.


Found it! Just where I left it 5 years ago ;) It is a bit faded, stained and tattered, but still fully readable. (banana)

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" DC current 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! @= ;) (lol)

/ed B
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Re: Cheap power iron at the e-place (the ten pounders)

Postby EWBrown » Wed Dec 02, 2015 9:39 pm

With a full wave bridge, the DC voltage would be approx. 280 to 320 VDC, depending on the filter caps and the DCR of the filter choke, and current loading.

For a voltage doubler, the DC voltage would be approx. 560 to 640. VDC, also depending on the filter caps and choke's DCR, and current loading..

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

Postby burnedfingers » Fri Dec 04, 2015 4:40 am

Which method of rectification would be best with this transformer?

I tried to upload a SS bridge with a damper diode tube picture. Also, what about a hybrid rectifier or hybrid rectifier with backup diodes?
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Re: Cheap power iron at the e-place (the ten pounders)

Postby DeathRex » Fri Dec 04, 2015 9:37 pm

What kinda amp, and what voltage and current are you wanting? If you're using a rectifier like pictured, put a filter cap after the bridge and after the tube, it would be equivalent to CRC filtering.
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Re: Cheap power iron at the e-place (the ten pounders)

Postby burnedfingers » Sat Dec 05, 2015 5:44 am

Thanks for the reply. After playing with a friends little 13EM7 SE amp I figured I would build one. If memory is correct Fred was the first to play with the 13EM7 Se amplifier in about 1998 and published the design in dogstar around 2002 and after that others copied the basic design. I plan to use the transformer (big one) simply because I have it and build a 6EM7/13EM7 amplifier. Ahead of this on the same chassis I wish to have a linestage section.

The piece of copper I happen to have on hand will handle the large transformer and the Hammond 125ESE's. I think I will use a 6sn7 cathode follower linestage and then the 13em7/6Em7 output stages. The high gain 6Sl7 side of the tube will have a HV PNP CCS load. The 44volt bias winding I'm thinking will have enough to provide the 35-40mA bias I need for the output section of the tube. Since the copper plate already has a hole in it for a rectifier I figured I would use a SS bridge and then a 6DW4 damper to provide a slow b+ turn on.
So, this transformer has enough 6.3 windings that I hope to put two in series to provide a method of supplying heater voltage to power up the 13volt tubes. I plan a DPDT switch to allow me heater control to do this. So, if I'm thinking this thru correctly one winding for the Damper tube. Two windings in series to provide 12.6 volts so that 13EM7's and 12Sn7's can be used. The large 6.3 volt winding to provide heater for 6Sn7's and 6EM7's.
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