Hairball power transformer troubles..

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blackbird

Active member
Joined
Jun 11, 2012
Messages
37
Hi all.
Im new around these parts.. very nice...

Im putting together a Rev a mnats with hairball audio kit.. I have a problem at the first hurdle.
Ive wired the power transformer the same as my friends one. Same transformer from hairball.

His voltages read 30v, 0, and 30.. which i assume is correct, as his is a finished working unit...

Mine reads 25v(brown), 46.5v(orange+red), and 68.5v (yellow)..

Ive wired the transformer with the grey soldered to vilot, and blue and brown straight from on off switch...

This is without anything other than the power transformer connected..
Any help much appreciated.

Thanks
Dave
 
You don't have Blue and Brown soldered together do you?  That would be very wrong.

The transformer does not have a brown sec lead.  Do you mean black?  They should read +25V at black and yellow against the center tap UNDER LOAD.

Have a look at the MNATs wiring pages again and be sure to read the Mark Burnley guide linked on there. 

Be careful.

Mike

 
Hi Mike.

I dont have blue/brown soldered together.
I have grey/violet soldered together..

The blue and brown leads come straight from the power switch.

I got the colours wrong in my first post... I meant black, not brown! Thanks for spotting that..

I get 25v at black, 46.5v at orang+red, and 68.5v at yellow...

Any other ideas?
Thanks for ya help

Cheers
dave
 
What are you using as your common/0V reference?  You should use the orange-red as your common and measure that against black and yellow.  Sounds like you're probably fine, just using the wrong common point.

25V between black - org/red
25V between Yellow - org/red
 
blackbird said:
I get 25v at black, 46.5v at orang+red, and 68.5v at yellow...
Click to expand...
against what ?
Have a look at http://www.avellindberg.com/transformers/tech_notes/tech_notes3.htm
For 240V AC mains you want your transformer hooked up as shown in the lower right pic.
Join orange and red for your secondary center tap connection.
Set your multimeter for measuring AC volts in a range higher than expected, maybe 200VAC.
Take your black meters probe, connecting to the multimeters COM port with tip probing the orange/red center tap connection .
Take your red meters probe, connecting to the multimeters V port with tip probing the black transformer secondary wire and read the amount of AC voltage between these two potentials.
With your black probe still at the center tap connection probe the remaining yellow secondary wire with your red probe. Readout will be similar than the last measurement.

uups. Mike got it faster.
 
Hi all..

I was using the chassis as ground to measure the points..
I used this method to check the voltage on the finished working unit too, and it was fine...

I guess i wasnt sure if i should assume the red/orange is earth. And it seems i have 25 volts sitting there on that earth point.

Cheers
Dave




Echo North said:
What are you using as your common/0V reference?  You should use the orange-red as your common and measure that against black and yellow.  Sounds like you're probably fine, just using the wrong common point.

25V between black - org/red
25V between Yellow - org/red
Click to expand...
 
Ok, so i did more tests, and more confusion has resulted...

With the working finished unit, if i disconnect the secondary wires (from power transformer) from the terminal block before it hits the main pcb, I get 2x 35v, and 2x50v.. When i join red and orange as it was, the voltages go to 30v, 10v, and 30v.. Which is correct..

When i do the same test with mine, exact same setup, i get the same reading when the secondary wires are separated from eachother (2x35v, 2x50v), but it all goes whack when i join the orange and red...  When i join those wires, i get 25v on black, 55v on orange/red, and 63v on yellow..

So confused..
Any help appreciated.

Cheers
Dave
 
blackbird said:
I guess i wasnt sure if i should assume the red/orange is earth.
Click to expand...
Assume it is not. This transformer secondary center tap junction will become your 0V reference voltage. If this reference voltage will as well get connected to your always mains safety ground connected case in a later stage with a more or less conducting bolt/washer/nut and an isolating coating of your case in between has nothing to do with your transformers secondary wires in the 1st.place.

With the working finished unit, if i disconnect the secondary wires (from power transformer) from the terminal block before it hits the main pcb, I get 2x 35v, and 2x50v..
Click to expand...
You get maybe 30V AC when measuring your unloaded secondary winding between black and red.
You get maybe 30V AC when measuring your unloaded secondary winding between orange and yellow.
You get maybe 60V AC when measuring your unloaded series combined secondary windings between black and yellow with red and orange joined together.

When i join red and orange as it was, the voltages go to 30v, 10v, and 30v.. Which is correct..
Click to expand...
probably not.

When i do the same test with mine, exact same setup, i get the same reading when the secondary wires are separated from eachother (2x35v, 2x50v), but it all goes whack when i join the orange and red...  When i join those wires, i get 25v on black, 55v on orange/red, and 63v on yellow..

So confused..
Any help appreciated.
Click to expand...
Maybe don't insist on your measuring methods and read previous posts again?
 
Hi all..

I apologize if i came off unmovable in my methods. Im not at all!. Just didnt understand..
I dont have the knowledge to have strong opinions at all!!

After doing exactly as you all have suggested, the readings came out spot on..
Thankyou all...
I also stuffed, soldered, and tested the power supply section on the pcb, and all is great..
The main thing that clicked for me, after explained by a friend, is how voltage is relative..

Expect more silly questions in the next few days whilst i get this thing going.
Most of the board stuffed, so hoping to get to the wiring in a couple of nights..

Cheers
Dave



Harpo said:
blackbird said:
I guess i wasnt sure if i should assume the red/orange is earth.
Click to expand...
Assume it is not. This transformer secondary center tap junction will become your 0V reference voltage. If this reference voltage will as well get connected to your always mains safety ground connected case in a later stage with a more or less conducting bolt/washer/nut and an isolating coating of your case in between has nothing to do with your transformers secondary wires in the 1st.place.

With the working finished unit, if i disconnect the secondary wires (from power transformer) from the terminal block before it hits the main pcb, I get 2x 35v, and 2x50v..
Click to expand...
You get maybe 30V AC when measuring your unloaded secondary winding between black and red.
You get maybe 30V AC when measuring your unloaded secondary winding between orange and yellow.
You get maybe 60V AC when measuring your unloaded series combined secondary windings between black and yellow with red and orange joined together.

When i join red and orange as it was, the voltages go to 30v, 10v, and 30v.. Which is correct..
Click to expand...
probably not.

When i do the same test with mine, exact same setup, i get the same reading when the secondary wires are separated from eachother (2x35v, 2x50v), but it all goes whack when i join the orange and red...  When i join those wires, i get 25v on black, 55v on orange/red, and 63v on yellow..

So confused..
Any help appreciated.
Click to expand...
Maybe don't insist on your measuring methods and read previous posts again?
Click to expand...
 
blackbird said:
The main thing that clicked for me, after explained by a friend, is how voltage is relative..
Click to expand...

People use the term "ground" a lot when they mean "common".  As Harpo explained, common is just a common reference point that may or may not be attached to actual ground.

Another one is how often you see "balanced" and differential" (wrongly) used interchangeably.
 

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