ESP Project 19 with LM3876 Keeps Muting Itself - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 1st January 2009, 08:06 PM   #1
diyAudio Member
 
jackand08's Avatar
 
Join Date: Oct 2008
Location: England
Default ESP Project 19 with LM3876 Keeps Muting Itself

Hi everyone,

I have just put together two LM3876 chip amps according to the circuit on Rod Elliots page here. I have assembled them on boards of my own design and the traces are all correct. When I power up the amplifiers with my bench-top PSU at 25v and no current limiting, the amplifiers will play music for around 5 seconds or less, then turn themselves off (when they have turned themselves off, the current draw goes down to about 10ma). This is the same with both amplifiers and happens each time the amps are turned on. My first thoughts were that the protection circuit was operating because the speaker I was playing playing the music through had a too low impedance (4ohm) so I hooked up an 8ohm speaker and the same happened again. I also thought that it could've been overheating and the thermal shutdown operating but a heat check on the chip itself and the heatsink proved me wrong. Although on Rods page it says the mute circuit was disabled I thought that this could possibly be the cause (just not to sure). BTW my music source is an iPod. Could anybody help me with this as I'm pretty baffled why it is doing this.
  Reply With Quote
Old 1st January 2009, 08:13 PM   #2
diyAudio Member
 
XEAGLEKEEPER's Avatar
 
Join Date: Jan 2006
Location: central Iowa
Without any source signal, do you measure any DC offset at the output?
__________________
Ret. USAF... AKA- Avionic *** Solder slinger for hire...***
  Reply With Quote
Old 1st January 2009, 08:14 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
and also check the voltage on the mute pin.
__________________
regards Andrew T.
  Reply With Quote
Old 1st January 2009, 10:35 PM   #4
diyAudio Member
 
Join Date: May 2008
Default Re: ESP Project 19 with LM3876 Keeps Muting Itself

Quote:
Originally posted by jackand08
When I power up the amplifiers with my bench-top PSU at 25v and no current limiting, the amplifiers will play music for around 5 seconds or less, then turn themselves off
Rm (R1) must connect with one leg to -25V. The other leg goes to LM3876 pin 8 and the negative side of Cm (C6). The positive side of Cm goes to ground. Your description sounds as if you had -25V and ground mixed up.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 2nd January 2009, 11:58 PM   #5
diyAudio Member
 
jackand08's Avatar
 
Join Date: Oct 2008
Location: England
Thanks for all of the answers, I have checked that the resistor goes to the -25v supply and the negative lead of the capacitor is connected to the resistor, however, I haven't tested the DC offset at the output. I try doing that and post the results later.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LM3876 for small sub amp? phreeky82 Chip Amps 11 5th July 2006 05:50 PM
LM3876 for guitar? Wynand Chip Amps 4 2nd November 2005 08:26 AM
Lm3876 bobossa Chip Amps 1 1st March 2005 04:18 PM
hi - LM3876 problems... RichardA Chip Amps 7 14th September 2004 04:32 PM


New To Site? Need Help?

All times are GMT. The time now is 02:43 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2