I don't think I'we gotten the part about grounding or the way to wire up a center taped transformer right. Since English is not my main language, I have a little trouble understanding how to propperly ground the Pcbs and transformer. I therefor drew up a quick schem of how I think the offboard wiring should be done, and would love if anyone would care to comment any mistakes. I was also wondering if it is important to have insulated jacks? I forgot to add a fuse on the drawing, by the way.
In the Manual for the Lm1875 amp, it says thet Chassis-ground(CHG) should be connected to a point on the chassis. I can't, however, find a hole named chg on my pcb's. Any help is appriciated.
Quick drawing of how I think it should be done:
My guess on the offboard wiring (http://i36.photobucket.com/albums/e48/syndromet/layout.jpg)
I started a thread about grounding methods few days ago, lot's of useful info there. What are those two round things in the picture?
Quote from: teemuk on August 23, 2006, 05:04:57 PM
I started a thread about grounding methods few days ago, lot's of useful info there. What are those two round things in the picture?
Hi,
I read your grounding thread, great stuff. This is just a way for me to confirm that I got things right, so I don't blow the amp up, when I get to put it together. The round things are supposed to be speakers. :o
Have you looked at this:
http://cordova.asap.um.maine.edu/~raymondj/imagehost/lm1875.pdf ?
In looking at that, there are three grounding points off the power board. One goes to each ground of the power in section on the amp boards (labeled GND) and the last one goes to chassis ground. Hope that helps.
In my opinion there's an insufficient amount of grounding nodes on that power supply board if more than one amp board is used. Now, you should figure out how to add more of them. For example, an external set of ground lugs (http://unimaxsupply.com/tatparts/sc8a.JPG) mounted to chassis by a single bolt in close vicinity to power supply board ground node might work. You could make this the main ground point and hook it up to the supply board ground conection with a single thick wire. Also, why connect the speaker ground return to the amp board in the first place when it should go straight to main ground point.
I appriciate the help, guys!
ok, so if I got this corectly, on the original layout the only connections to Chassis ground should be from the power supply and the mains connection? But i should run all grundpoints to chassis ground to have it opperate as quiet as possible?
How important is insulated jacks? And how do I wire up a center tapped transformer?
Guess thats enough questions for now.