What a hell is this? - Page 1
Forum section: electronics / projects

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 11:53:38 am
content: ok first of all i thought im gonna make pcb myself but i dont have a drill so im stuch with this board. i have built the amplifier based on lm3886t IC and its not working i have few questions1 how do i diagnose the problem given in mind i only have a multimeter2 im pretty sure i did everything right coz its not so hard to build and follow the traces could circuit be wrong?3 what a hell are those unnecessary traces or whatever you wanna call it in picture 3 how do i remove them?4 i give up i will use a company who make pcb boards what should i give them as a pcb design? how does it work? they ask me to convert eagle format to Gerber RS-274x how do i do that and how do i determine the size of the pcb?pcb file from eaglehttp://www.failai.lt/volslhqxc3xz/SP0001.brdimages

author: McBryce
author_rank: Super Contributor
timestamp: July 28, 2015, 12:05:03 pm
content: Hi Justin,I can't answer everything here, but here's a few answers:1 - Difficult. I'd start by at least confirming voltages and currents such as the supply voltage to the LM3886 IC.3 - Those dotted lines are a polyline, usually used to define the borders of a ground plane. Try right-clicking on one, then choose rename (choose all segments) and re-name it to GND. This should fill the empty space with a ground plane. The smaller inner polyline seems to be defining a "keep-out" area.4 - There's a dimension tool in Eagle (fourth button from the bottom on the left) which you can use to measure the PCB.A few further questions on getting it working / diagnosing: What are you powering the PCB with? Have you a proper split rail supply for it? How many amps are the two rails pulling? What signal are you injecting into the amp to test it?A further tip: The LM3886 has that massive tab on the back for a reason - It gets hot, very hot when working. Strap a big heatsink to it, otherwise it won't be working for very long when you do get it up and running.McBryce.

author: rs20
author_rank: Super Contributor
timestamp: July 28, 2015, 12:06:44 pm
content: 1, 2. What's the problem? "It's not working" isn't enough information.3. Are those traces, or are they DRC error markers showing you that your traces are too close to the edge of the board? Did they appear only after you did a DRC?4.http://lmgtfy.com/?q=eagle+export+gerber

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:18:12 pm
content: Quote from: McBryce on July 28, 2015, 12:05:03 pma big THANKS for reply im powering it either with switching 50w 12v power supply or with a non switching transformer like this 23.7v DC kind ofhttp://www.part.lt/img/7bb34f037aa75e7ba46aadde9a851da2543.jpg

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:24:50 pm
content: Quote from: rs20 on July 28, 2015, 12:06:44 pm2 yes its not working and i dont know why and it has v- v+ and gnd witch one of those should i use?3 i have no idea i have downloaded this project files and i have no idea about whats happening im a noob when it comes to pcb designing and understanding stuff. can you help? this is the site i have download fileshttp://andy-progetti.com/small-and-high-performance-audio-power-amplifier-lm3886/#comment-98

author: McBryce
author_rank: Super Contributor
timestamp: July 28, 2015, 12:27:56 pm
content: Quote from: justin66 on July 28, 2015, 12:18:12 pm??But it needs a split rail +V / 0V / -V to work? Why would you think that it would work with a 12V single rail supply? Where are you even connecting the 12V to?McBryce.

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:29:16 pm
content: oh fu** im noob

author: McBryce
author_rank: Super Contributor
timestamp: July 28, 2015, 12:32:05 pm
content: Let's take a step back. What do you want to amplify? Can it be done with a single rail supply amplifier? If so, check out some single rail designs.McBryce.

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:32:16 pm
content: Quote from: McBryce on July 28, 2015, 12:27:56 pmshould i build one of thiese?some howhttp://farm6.static.flickr.com/5063/5619660342_6dc9a5697e_b.jpg

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:39:25 pm
content: Quote from: McBryce on July 28, 2015, 12:32:05 pmok i want power two 8ohm woofers connected in paralel each one is 300 chinise watts and maybe 60-120w rms as for now im powering it with tda 2050 but if i turn volume more than 50% it distorts like crazy so i figured i need more powaaa. and i found decent chip amp that can do it for the most part.http://www.part.lt/img/3d29a568a92172347997ba5fa6fa2849702.jpg

author: McBryce
author_rank: Super Contributor
timestamp: July 28, 2015, 12:40:03 pm
content: Quote from: justin66 on July 28, 2015, 12:32:16 pmNo definitely not. The proper way to do it is with a transformer that has a centre tap like this:http://www.homemadecircuits.com/wp-content/uploads/2014/08/dual-voltage-power-supply.jpgIt doesn't have to be that complicated, this example is for variable voltage output, you can use fixed value regulators to reduce the part count.McBryce.

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 12:47:51 pm
content: but can i fake the ground just to test the circuit somehow?

author: McBryce
author_rank: Super Contributor
timestamp: July 28, 2015, 12:53:19 pm
content: Yes, several ways:1 - Use two isolated PSUs with the positive of one connected to the negative of the other.2 - Use a PSU with twice the voltage you need and create a virtual ground with a resistor divider.McBryce.

author: justin66
author_rank: Regular Contributor
timestamp: July 28, 2015, 01:04:12 pm
content: a big thanks mate

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2015, 02:35:45 pm
content: Figure 3 on page 6 of the datasheet shows a configuration which will work on a single supply rail. Note how a potential divider followed by an emitter follower is connected to pin 7.http://www.ti.com/lit/ds/symlink/lm3886.pdf