I am finally getting around to finishing up my Lm3886 kit. I have a transformer from a home stereo i want to use.
First off can I do that, secondly how do I know what wires go to my power supply board. I have the 2 ac input wires and there
are 5 wires from the secondary side. There are 2 reds and 2 blues and one black wire. The AC voltage varries depending on where I'm measuring from. Where should I be testing and what should I be looking for? Thanks for any help.
Post a drawing showing the following voltages:
Red/Red
Red1/Black
Red2/Black
Blue/Blue
Blue1/Black
Blue2/Black
Red (any) to Black(any)
What power was the original Home Stereo?
Unsure of the original wattage, its an old Sherwood reciever, no wattage markings.
The wires in the picture are left to right; Blue 1, Blue 2, Red 1, Black, Red 2.
Red-Red: 51.6vac
Red1-Black: 25.8vac
Red2-Black: 25.8vac
Blue-Blue: 7.4vac
Blue1-Black: 16.8vac
Blue2-Black: 11.0vac
Red1-Blue1: 5.3vac
Red1-Blue2: .5vac
Red2-Blue1: 39.2vac
Red2-Blue2: 34.4vac
(http://i91.photobucket.com/albums/k288/fixr1984/Amp/2012-03-08_20-25-39_28.jpg)
My guess,, Red /Black /Red are the main power amp wires.
They being 26-0-26 VAC delivering approx 35-0-35 VDC when rectified.
(perfect for driving the LM3886 Chip). Go for it. :dbtu:
My guess,, blue blue delivers the next voltage for driving aux stuff,,, light bulbs.
You may not even need these.
Phil.
Thanks. The next part that confuses me is where to hook up the wires to the power supply board. Do I run a red on each side and "y" the black to go to both sides?..AC always confuses me:)
http://sound.westhost.com/power-supplies.htm
adding a couple of pics that might help.
Don't touch anything you can't outrun winky.
Phil.
Your Black goes to the Ctap (often also grounded to chassis)
The 2 Red wires then go to rectifier.
Phil.
Sorry to keep asking the same thing over and over but I'm really scratching my head. Looking at the pictures it makes sense but I have spaces for 4 wires to hook up to the board and thats where I'm getting lost. I should add that I have the kit from chipamp.com
Here is a picture I found showing you what I mean. There are 2 wires going to each side and I'm lost......So I run a red wire to each side then what is the other wire? This is like my kit but not the stereo version.
http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs394.snc4/45718_462598446252_637721252_6971417_7709811_n.jpg
Thanks for putting up with me. ;)
In your case there will only be one wire going to each side since you don't have a split secondary.
One red wire to each side. Black for the center tap. And you can tape up the extra secondary wires and leave them disconnected.
The chipamp suggested has a dual secondary transformer, and a dual bridge rectifier.
Not wrong, but not the common way to do things.
I *guess* they do so, to make you buy their full kit (nothing against that).
Post the Power supply schematic you have and we'll suggest how to wire it to your transformer.
Here's the schematic.
What I did that seemed to work for the power supply board was to run one red to AC1 and the other to AC2 and then I took the black wire to the other AC1 and AC2 spots. Not sure if that was right or not but I was able to get a good DC reading from +v and +PGND.
I do pop a fuse when I try to connect the amplifier board. It only happens when I hook up all 4 wires. If I have either just the + wires connected or just the - wires it wont blow the fuse. Is this an issue with the way I have the AC wires connected or an issue with the amplifier board.
(http://i91.photobucket.com/albums/k288/fixr1984/Amp/F02-LM3886-power-supply.png)
Your best bet is to discard that rectifier setup; it needs two isolated secondary windings, which your transformer doesn't have.
Use only a single rectifier like suggested in former posts.
Post 2 close up pictures of that board, you´ll have to reform it a little, cut some tracks and add some wire bridges.
You *can* use it that way.
Try to show tracks clearly.
Its hard to see the traces on the top of the board. Hope this helps
(http://i91.photobucket.com/albums/k288/fixr1984/Amp/DSCN1105.jpg)
(http://i91.photobucket.com/albums/k288/fixr1984/Amp/DSCN1104.jpg)
That board was designed to *force* you to buy a Dual Secondary Poweer Transformer.
This is a way to use a surplus center tapped transformer, the most common kind.
You'll need to buy an extra Bridge Rectifier.
I suggest the KBU8D, available at Mouser
http://www.mouser.com/Semiconductors/Diodes-Rectifiers/Bridge-Rectifiers/_/N-2xpqk?P=1z1414hZ1yzv2qbZ1z0waqaZ1yzxpge
It's a rectangular plastic package with a mounting hole, which allows it to be bolted to the chassis and its legs bent upward and cut to a length of, say, 1/2", so you can solder wires to them.
It has 2 "AC" legs where you will solder the transformer wires, and a + and a - legs which are connected to AC1 and (-)AC2 terminals.
The transformer center tap goes straight to the PCB output ground: both PGnd which are joined together.
After this mod, the PSU board outputs feed the amps as usual.
(http://img207.imageshack.us/img207/4030/dualsec2ct.gif)
Thanks, I will give it a try.
I had an RS604 lying around so I gave that a try. I get dc voltage where I am supposed to now and with a speaker hooked up and my mp3 player to the input i get an amplified sound. I cant get the LED to light up tho. I only get 1.2vdc on the led pads. Is this because of the board layout and using a different transformer? I dont really care if the LED will light up as long as the board is working properly.
Fine so far.
Congratulations.
Post the schematic of your Led wiring.
What's the DC voltage you actually have on the Power Amp?
Its too hard to see what is going on with the mask on the circuit board, it looks like there is a diode coming off of AC1 and from there it goes to a resistor and then to the led. (crappy description i know). As far as power I have. 51.7VAC from the transformer, out of the RS604 I have 47.0 VDC, and from the output pads of the power supply board +V and -V I have 67.2VDC
1) an image is worth 1000 words , draw what you have,
2) repost your voltages relative to ground.
I have decided not to use the power led setup from the power supply board so that is no longer an issue for me.
I measure 33.5VDC from +V to ground. Everything seems to be working fine, I've done some testing into a speaker and it sounds pretty good. Just need to get my preamp done. Had a buddy bend me up a chassis so things are finally coming together.
Fine.
Still need -V to ground.
In a split supply as yours both values need to be quoted.
Good luck.
Yea I probably should have posted that. It is -33.5VDC.