Question about Computers & Internet
We are building a mini laptop by assembling a Single board computer (SBC), DC-DC converter (24V i/p 5V and 12 V o/p ), LCD, mouse, 4x4 matrix keyboard etc.. for a particular application.
We have one more module which is connected to SBC through PC104 and line-in.
We have designed a PCB which holds this module and SBC together. It is used for routing lines of pc104, audio, mouse, usb, vga, ethernet etc. It is multi layered and one layer is ground (reference line) itself.
We have used 2W audio amplifier ST TDA7268 which takes i/p from line-out and feeds to a 8 ohm speaker.
computer is loaded with Windows XP.
All the modules work fine when tested seperately..
Problem: When the computer is on there is a constant humming noise (loud enough) in the speaker. Also while moving the mouse (no matter usb or ps2) some other noise adds to it. Same is the case if you keep pressing a key in the keyboard.
If you mute line-in (in windows) there will be no noise. (but we can't do that as we are connecting our module to line in). Can't just blame on that module because this module is working fine in some other application without any noise.
Noise persists u completely dettach the module (dettach its power in, dettach from line in and pc104 of SBC).No matter line in is on or off (in windows).
No noise if you connect the module to only power and pc104 (dettach line-in connection). Once Line-in is connected(on board) and make line-in on(windows), noise appears.
I think problem is with grounding. We are using 24V DC battery as power supply and there is no earthing.
Please help me how to find the source of noise... Also if it is problem with noise how to solve it. (we cant change pcb design)
Solder a .001 uf ceramic capacitor between all audio signal lines and ground
Posted on Jan 18, 2009
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Nov 01, 2012 | Toshiba 65HT2U 65" Class Full HD LCD HDTV
Jul 26, 2012 | Samsung LE32R41BD 32 in. HD-Ready LCD...
Oct 18, 2010 | Samsung LN-T4665F 46 in. LCD Television
Aug 30, 2010 | Dell Inspiron 1525 Laptop
Aug 22, 2010 | Dell Inspiron Mini 10 Notebook
Jan 05, 2010 | Dell W2600 26 in. LCD Television
Dec 14, 2009 | Insignia IS-LCDTV32 32 in. Television
Dec 09, 2009 | Audiovox FPE3206 32 in. LCD Television
158 people viewed this question
Usually answered in minutes!