Brian GT chip amp build Questions

[guycom]

Hi, I am building my first amplifier and had two questions. How do I know if the led is positioned correctly? Second I have a large iron core transforme with three secondery wire-- ca I shre the cener tap with both boards.
Thank You for your help,
Guycom

 

[wboyd]

I believe that long tail of the LED is the pos terminal....don't shoot me if I am wrong....but it is listed somewhere in the manual. I think that there is a marking on the PS board showing where the long tail is supposed to go.

As for your transformer situation...I have a question for you. Are you saying the the transformer has 3 secondary widings (6 wires), or it has 3 wires coming out of it (ie 2 colored wires and common). If the second situation is the case then there is a certain way that you should setup your PS (which escapes me at the moment) but do some searching in the chip amp forum and you will find it.

Have a good one,

Wayne-o

 

[guycom]

Thank you, I will check the led and board. Yes the xfmr has three secondary wires . Regards
Guycom

 

[john blackburn]

Also theres a flat section on the body of the led which indicates the negative leg.
It comes in handy if using second hand leds or ones that have had the legs cut previously.

 

[danielwritesbac]

Just a sec to verify. .. so the transformer has 2 wires on one end for input and 3 wires on the other end for output--a normal center tap transformer?

If so, check out the photo at this post:
http://www.diyaudio.com/forums/showthread.php?postid=1415611#post1415611

On a center tap transformer's power supply, each amplifier has only one ground wire from power supply to amplifier. That terminal is marked "CG" on your amplifier boards.

You can do a stereo layout (powers both amplifiers) nicely, if you make all the wires exactly the same length for both amplifiers.

I think the rest is on that post.

 

[guycom]

Hi, Thank you for your help. The long leg of the LED will go in the led marked hole in the board that is square with a arrow next to it. I powered up the board and that is the one that shows pos polarity.
Thanks again for the pictures and info
Guy