Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hi guys.  I was going to use the transformer out of an unused (but working) home entertainment sub for a LM3886 project.  The caps on the board are 35v, and the transformer is huge, so thats a good sign.  Anyway, the mains power is connected to the transformer on FOUR wires.  Black from the wall goes to black and red on the transformer and white on the wall goes to white and brown on the transformer.  Then on the other side of the transformer there are three wires, two red and a black.  What's with the 4 wires on the primary side?  Or is this thing maybe hooked up backwards?

HI Joe:

I wondering if the 4 wires at the "pseudoprimary" maybe means that your tranny have two primaries windings. The fact that they are joined make me suspect this. Maybe black and white is one winding and red and brown another. Other posible combination is black and brown, one winding, and white and red, another.


Perhaps your tryied measuring with a tester continuity between each pair of wires?

Hope helped

Quote from: polo16mi on August 27, 2009, 11:22:33 AM
HI Joe:

I wondering if the 4 wires at the "pseudoprimary" maybe means that your tranny have two primaries windings. The fact that they are joined make me suspect this. Maybe black and white is one winding and red and brown another. Other posible combination is black and brown, one winding, and white and red, another.


Perhaps your tryied measuring with a tester continuity between each pair of wires?

Hope helped

Do you ever have two sets of primaries?  I haven't taken it out of the sub yet, so I can't take any measurements.  I'll probably get to that this weekend.

"have two sets of primaries? " -> yes, all the time.
It sounds like two identical 120V primaries to me, wired in parallel.
Wired in series they will become a 240V primary.
You should use it as-is, since you have 120V.
Measure the secondary AC voltage, and/or the rectified +/- voltage. That will give you a pretty good idea of what can you use it for.

Quote from: J M Fahey on August 27, 2009, 03:50:15 PM
"have two sets of primaries? " -> yes, all the time.
It sounds like two identical 120V primaries to me, wired in parallel.
Wired in series they will become a 240V primary.
You should use it as-is, since you have 120V.
Measure the secondary AC voltage, and/or the rectified +/- voltage. That will give you a pretty good idea of what can you use it for.

Awesome.  I was planning on measuring the AC voltage after it is disconnected from the circuit.  This is how I normally scavenge transformers.  I just hadn't heard of them being wired like that with two sets of primaries.  Pretty cool that I could set it up to run on 220v, although not necessary.  Thanks!  (You get big chip points for this one bud)