Trafo for Chipamps lm3886

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Maxhax

Member
Joined 2009
Hello everyone!

I recently bought the lm3886 stereokit from BrianGT, and while looking for a trafo I found a broken Monacor DSR-200 surround reciever at home, I decided to take a look at the trafo, to see if I could use it.

The trafo is rated at 520VA at 230v

I removed the trafo and connected it, I measured the ac voltage on the outputs.

This is the results:
1+2=21v
1+3=42,5v
1+4=21v
1+5=29v
1+6=59v
1+7=90v
1+8=98v
1+9=10v
1+10=8v

2+3=21v
2+4=3v
2+5=11v
2+6=41v
2+7=71v
2+8=79v
2+9=1v
2+10=3v

3+4=15v
3+5=7v
3+6=23v
3+7=53v
3+8=61v
3+9=11v
3+10=13v

4+5=9v
4+6=45v
4+7=81v
4+8=90v
4+9=2v
4+10=3v

5+6=35v
5+7=71v
5+8=81v
5+9=6v
5+10=7v

6+7=35v
6+8=45v
6+9=20v
6+10=22v

7+8=9v
7+9=35v
7+10=36v

8+9=38v
8+10=40v

9+10=5v

I hope it didnt get to messy.

When I measure if the pins are connected to eachother (Ω=0 Ohm) I get the follow results:

1+2+3=connected
4+5+6+7+8=connected
9+10=connected

Oh well, I've got no clue what this means and I've got no clue at all how to connect it to the PSU.

Softstart required?

Anyone mind giving me some help on how this work, and which pins to connect to what.

Adding some photos for you:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.



Thanks

Maxhax
 
A

AndrewT

R.I.P.
Joined 2004
first:disconnect the mains.
second: find which outputs are on a common winding and how many windings it has.
third:connect the mains via a light bulb tester.
fourth:
measure the voltage ONLY across terminals of a single winding.
Measure each winding and all it's tappings separately.
Now tabulate your results.
 
M

Maxhax

Member
Joined 2009
Thanks for the fast answer, I'll build a light bulb tester asap.
AndrewT said:
first:disconnect the mains.
second: find which outputs are on a common winding and how many windings it has.
third:connect the mains via a light bulb tester.
fourth:
measure the voltage ONLY across terminals of a single winding.
Measure each winding and all it's tappings separately.
Now tabulate your results.
Click to expand...

How?
 
A

AndrewT

R.I.P.
Joined 2004
if 9 & 10 are the same widing and NOT connected to any other tap, then DO NOT measure 9 to any other tapping nor 10 to any other tapping.
Similarly, if 1, 2 & 3 are on one winding then do not measure any of these taps to any other tap.

Now repost the correct data.
 
pheonix358

pheonix358

Member
Joined 2008
AndrewT said:
if 9 & 10 are the same widing and NOT connected to any other tap, then DO NOT measure 9 to any other tapping nor 10 to any other tapping.
Similarly, if 1, 2 & 3 are on one winding then do not measure any of these taps to any other tap.

Now repost the correct data.
Click to expand...

Hi Andrew,

I realise you are providing some education on how to do this properly. The information is all there, just messy with a great deal of redundant info.

Maxhax,

1,2 and 3 are a 42V centre tapped winding. Pin 2 is the centre tap. Let's call this winding A.

4,5,6,7, and 8 are winding B. Pin 6 is the centre tap. Using 4,6 and 8 you have a 90V centre tap, using 5,6,7 you have a 70V centre tap.

9 and 10 are a 5V winding lets call this Winding C.

Assuming bridge rectification

Winding A will give you around +-30V DC
Winding B taps 4,6,8 will give you +- 64V DC
Winding B taps 5,6,7 will give you +- 50V DC
Winding C will give 7 V dc.

The only winding suitable for a 3886 is winding A. The question you need answered and I can't answer it from the info supplied is how much current winding A will give you. It will not be any where near 520VA. Winding B is the winding with all the current. If you have a look at the donar amp you will probably find some chip amps. Count them up and look at their data sheets. This will tell you what the chips need in terms of current. Otherwise find a service manual or schematic for the donar and see if that gives you any more info.

All above voltages are approximate.

Terry
 
M

Maxhax

Member
Joined 2009
pheonix358 said:
Hi Andrew,

I realise you are providing some education on how to do this properly. The information is all there, just messy with a great deal of redundant info.

Maxhax,

1,2 and 3 are a 42V centre tapped winding. Pin 2 is the centre tap. Let's call this winding A.

4,5,6,7, and 8 are winding B. Pin 6 is the centre tap. Using 4,6 and 8 you have a 90V centre tap, using 5,6,7 you have a 70V centre tap.

9 and 10 are a 5V winding lets call this Winding C.

Assuming bridge rectification

Winding A will give you around +-30V DC
Winding B taps 4,6,8 will give you +- 64V DC
Winding B taps 5,6,7 will give you +- 50V DC
Winding C will give 7 V dc.

The only winding suitable for a 3886 is winding A. The question you need answered and I can't answer it from the info supplied is how much current winding A will give you. It will not be any where near 520VA. Winding B is the winding with all the current. If you have a look at the donar amp you will probably find some chip amps. Count them up and look at their data sheets. This will tell you what the chips need in terms of current. Otherwise find a service manual or schematic for the donar and see if that gives you any more info.

All above voltages are approximate.

Terry
Click to expand...

Awesome, now I think I understand how everything work.
I'll look up the chips on the amp asap I get back home.

Max
 
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