Power on the green pre

I just finished inserting all the components on my psu board and everything went great, however, I have a couple questions on how to finish it.

First, I bought both the Dagnall 30va power transformer and the cheap torroid from parts express. Which should I use?

Next, If I use the Dagnall, what pins go to the pwoer supply board? And how does one go about attaching wires to the little leads on the tranny. I noticed on the board that it says 15vac 15vac and 0v, so which pins go to these spots? Also, what should I do with the transformer, it looks like it's designed to go directly on a psu pcb, so what am i gonna do with it?
Now, i could just go with the torroid, but again, what wires go where?

I looked though the metas and came up with no answers on these questions

thanks

Here this may help.
http://www.groupdiy.com/index.php?topic=6096

First, I bought both the Dagnall 30va power transformer and the cheap torroid from parts express. Which should I use?

Click to expand...

Depends on the no of preamps. Not sure what the VA rating of the cheap toroid is.

Next, If I use the Dagnall, what pins go to the pwoer supply board?

Click to expand...

Need more detail.

it looks like it's designed to go directly on a psu pcb, so what am i gonna do with it?

Click to expand...

Buy some Verobaord (stripboard) & mount it on that.

If your transformers have 2 secondaries, make sure you connect them in phase.

Peter

I'm building a four channel, and the details of the torroid are linked above you post peter.

People on that thread seem to think that the cheap toroid is about 50VA, so it would be fine for up to 8 pres.


Peter

Ok, so what wires go where, there's 2 primaries, and two red secondaries and two orange secondaries.

nobody?

Hey PTown,

Did you ever get an answer to this question?

I'm wondering how to measure which leads are in phase before wiring the secondary. A little weird that they'd be the same color. Perhaps their arrangement in the header (connector) will be some use.

I guess I'll get out the voltmeter and see if something logical will hit me. But if you found a way to test, I'd like to know. Thanks!

Kato

Hi Kato

Here is a thread that describes how to find out the phasing of the windings.

http://www.groupdiy.com/index.php?topic=199786#199786

Also check the phasing of the primary if there are 2 x 115v windings.

Peter

PS check the name of the last poster! :wink:

Hi Peter, thank you, I remember that thread.

With a datasheet, this would be easy.
I just have the generic OEM torroid from the "a cheap torroid" thread with a single primary, and dual secondary. 2 black wires (primary) and 2 orange wires (secondary) and 2 red wires (another secondary.)

Also I have no function generator, only a DMM. (I will get one soon.)
Gyraf mentions that you can wire the secondaries in series to determine the phase. So I'm going to try that.

Now I wonder this, does the phase of the primary matter?
I'm assuming not, since often you find old houses wired in reverse and appliances still function OK.

Will I destroy the transformer if I wire the L and N in reverse?

I will try your cautious method, plug in for a few seconds, check for smoke, unusual smells, etc.

First, I must snap some chalk lines for a tile floor. Perhaps someone will answer in the mean time before I plug it in. (I've already wired it, I'm just hesitant to plug into mains without knowing for sure.)

Kato

I just re-read the post you linked to and it's pretty clear now that I MUST make sure the primary is in phase before applying power.

Thank you for saving me from destroying a transformer (and possibly worse.)

Now I've got to hurry up and get a function generator... ebay.

Thank you again,
Kato

----------just a few minutes later----------
It just occurred to me you're probably talking about a dual primary transformer when you mention wiring it in phase.

I imagined applying 1v with a function generator and realized, that if you don't have a datasheet, it's completely arbitrary which lead you choose to apply the positive 1v. So when you check that for voltage drop with your DMM, you're going to use the red lead instinctively. Sorry, I probably look like a complete moron.

I'm back to assuming it doesn't matter which primary lead is L and which one is hooked to "N."

I MUST make sure the primary is in phase before applying power.

Click to expand...

If there is only one pair of primary wires, there is no problem with phasing on the primary. It can only be a prob when there are 2 primaries.

I'm back to assuming it doesn't matter which primary lead is L and which one is hooked to "N."

Click to expand...

Either will work. Make sure the fuse & switch are in the side that corresponds to the Live side of the wall socket.

Do the Gyraf method to check the secondary phasing.

Peter

[quote author="peterc"]
Either will work. Make sure the fuse & switch are in the side that corresponds to the Live side of the wall socket.
[/quote]

Thanks Peter.

What does it mean if I blew a fuse immediately?
(it was a 500mA fuse.)

I plugged it in with no load. None of the secondary leads were touching.

I've also had this before with toroids, where the inrush current blows the fuse. Try with a 1A fuse, this seems to be my optimum value.

Peter

I picked up some 1.25A fuses on lunch break today.

The fuse held up and I think I've figured it out. Thanks for your help Peter, (and Jakob in another thread, and countless others who posted useful facts, not to mention mark burnley who created the transformer hookup chart.)

I arbitrarily labeled the secondarys 1, 2, 1, 2 (one of each color) and wired it hoping the "1s" would be in phase. But no, I got 15.1v AC between the center tap and either end. (After connecting Red-2 to Orange-1.)

That must mean my arbitrary labeling was wrong (50%/50%) so I then attached Red-2 to Orange-2 and got 30.6v between the two 1's.

Which I believe tells me that Orange-2 and Red-1 are in phase.

Does anyone know the power requirement for a single channel of green pre?

No more than 100mA per channel

Peter

woo hoo!
i can power like, 7000 channels!

im having a hard time finding a 30va trancformer in the US could someone please point me in the right direction.

How about Avel-Lindberg?

Come recommended from this board.

http://www.avellindberg.com/
Y236103

Peter