what should i do with this transformer?

RnFR · Post by **RnFR** » 17 Jan 2012, 04:30

i got this thing in a lot buy years ago, and have no idea what to do with it. it seems like some really nice iron, but right now it's just a big ass paper weight. any ideas? seems like the output might be a bit low, but maybe with some sort of doubler circuit?

diagrammatiks · Post by **diagrammatiks** » 17 Jan 2012, 04:38

go ahead and sell it to me?

RnFR · Post by **RnFR** » 17 Jan 2012, 04:40

no dice!

diagrammatiks · Post by **diagrammatiks** » 17 Jan 2012, 04:57

what do you need a 176vac at 700ma and a 97vac winding for anyway.

RnFR · Post by **RnFR** » 17 Jan 2012, 05:11

i'm guessing it was for some sort of "scientific" instrumentation. maybe i'll try a fancy 5678 amp. i think they can take 90v max. maybe use the other windings for 12AX7 preamp section? the current might be lacking though, huh?

diagrammatiks · Post by **diagrammatiks** » 17 Jan 2012, 05:44

you could run the 176vac winding for 250 around vdc.

you'd only be able to run 90 12ax7s with that transformer though.

RnFR · Post by **RnFR** » 17 Jan 2012, 06:35

no shit!

i didn't even realize the thing had AC output until you mentioned it.

mysticwhiskey · Post by **mysticwhiskey** » 17 Jan 2012, 06:47

I suppose you could connect the 97v and 176v windings in series to get about 380vdc out. Looks like a beast of a transformer.

diagrammatiks · Post by **diagrammatiks** » 17 Jan 2012, 07:10

RnFR wrote:no shit!

i didn't even realize the thing had AC output until you mentioned it.

transformer go ac-ac lolololol.

that thing has a 15a and a 12a 6.3vac secondary too.

don't lick it.

Dr Tony Balls · Post by **Dr Tony Balls** » 17 Jan 2012, 14:28

Thats a great transformer for a 100W Orange or Marshall type build. Its overspec'd in the current handling department, for sure, but nothing wrong with that. Check out the voltages spec'd on this mid 70s OR120 schematic: http://users.telenet.be/orangefg/OFG_SC ... post74.jpg

printer2 · Post by **printer2** » 18 Jan 2012, 02:41

Voltage doubler on the 176v winding, with 490vdc, drop some voltage for filtering 450V. 700mA rating, knock that in half for the doubler, multiply by 0.7 for capacitor filter gives you about 240mA. Build a stereo 20-30W amp.

RnFR · Post by **RnFR** » 18 Jan 2012, 06:02

of course PTs go ac:ac.

then rectified to dc. god, I'm so clueless about tube power supplies. thanks for the help guys. good to know I have options. once I get it all together I'm sure I'll have a shitload more questions.

btw- this thing is frickin massive! I got it and a ton of other parts years ago (including actives, passives, a breadboard, a rackmount enclosure, another couple boxes, 12v trafo, 6.3v trafo and bunch of other stuff including a bunch of notes)for 99$ from a dude that quit building. it really set me on my way.

phatt · Post by **phatt** » 18 Jan 2012, 14:18

Looks like you have a ton of power ,, google Voltage doubler circuits or maybe this might interest you.

http://www.ozvalveamps.org/ava100/ava100psu.htm

Remember voltage doubler stuff is a bit misleading, it's actually 2.8 times.

i.e. your 97VAC x 2.8 is about 270 VDC.
and your 176 VAC ends up close to 500VDC.

As has been mentioned the Amps have to be de-rated some folks miss this in the fine print

Oh and D/load this data you will need it to get your head around PSU design.
This one page helped me out years back when trying to understand the stuff needed to make PSU's

http://evatco.com.au/hamptchoke.htm

Click on this; *Transformer Selection Guide* (in middle of page)

Print it out,, you will need to refer to it often until you learn it. Winky.
Have fun,,Phil.

RnFR · Post by **RnFR** » 19 Jan 2012, 07:00

thanks for the good info!

marshmellow · Post by **marshmellow** » 19 Jan 2012, 19:00

I'd build a bench power supply for tube projects. It's perfect for that purpose with the seperate HV windings, since you can use those seperate or in series for higher voltage. Rectifier and a simple adjustable MOSFET regulator and you're good to go.

RnFR · Post by **RnFR** » 20 Jan 2012, 00:55

thanks! great idea, i'll look into that.

briggs · Post by **briggs** » 20 Jan 2012, 01:03

marshmellow wrote:I'd build a bench power supply for tube projects. It's perfect for that purpose with the seperate HV windings, since you can use those seperate or in series for higher voltage. Rectifier and a simple adjustable MOSFET regulator and you're good to go.

Yes, this - with the Mosfet regulator for the "power scaling" you'd be on to a very useful design tool..

RnFR · Post by **RnFR** » 20 Jan 2012, 03:36

is that a TUT design? got a link to a schematic somewhere?

phatt · Post by **phatt** » 21 Jan 2012, 11:17

To the best of my knowledge,,, google *Dana VVR* for Amplifiers up to around 40Watts.

Bigger amps?? You may need the King tut PS setup or like.

I've never seen the PS schematic except for the hand drawn schemo's in tut 2 book.

I was wishing to build a PS some years ago but I went with the Guytron concept instead as it was a *Known* working setup. That rig is a ReAmping system, 2 Amps in one head.

Tut 2 did not really have enough detail to outlay cash with confidence that it would work,, admittedly I did not have the required skill to take on the circuit at the time.

From my reading the scaling concept tends to be problematic, where at very low voltages the preamp becomes unbalanced with the power stage. (though tut reckons that can be compensated)
Pure simplicity is One of the reasons I opted for a Reamping setup.

If you want to play around with the HT,,For smaller amps (Value for money and simple to install) the VVR kit is probably the best bet.

By now someone has likely got a fully regulated and adjustable PSU circuit laying around the net land?? Maybe go search around.

Phil.
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