LM3886 - getting hot - low volume - 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 29th January 2007, 01:10 PM   #1
diarav is offline diarav  India
diyAudio Member
 
Join Date: Dec 2004
Location: Bangalore India
Default LM3886 - getting hot - low volume

I am in the process of building a 6-channel amp using LM3886. the schematic is from ESPs site http://sound.westhost.com/project19.htm . I made my own PCBs (3 channels on a single board).

5 channels are working fine (good output sound, heatsink just gets mildly warm, chips dont feel warm on touching..)

But one of them (same schematic, layout as the 5 above) actually gets hot within 15 to 20 secs of power on. While testing this the output volume suddenly dropped, and has been so since. I still have 2A fuses intact on the power rails.

I checked all components and they were soldered correctly. I dont see any short circuit, dry solder on the board.

Possible causes:
1) Possible damage to any resistor , capacitor during soldering (I am not very skilled !!).
2) Defective components as such.

Questions:

1) What is the first area / component to check/replace as the possible cause for this problem.

2) is my LM3886 chip possible damaged? I am still getting an output.
__________________
Regards,
Din
  Reply With Quote
Old 29th January 2007, 05:19 PM   #2
diyAudio Member
 
kuldeepsingh's Avatar
 
Join Date: Aug 2006
Location: Chennai, India
Send a message via MSN to kuldeepsingh
Arrow Compare this particular IC with other 4

is the pcb used is same as for the other 4 channels, just have a check on pcb tracks and whether any possibility of deburrs is there. And also check whether all components are well soldered.
  Reply With Quote
Old 30th January 2007, 04:15 AM   #3
diarav is offline diarav  India
diyAudio Member
 
Join Date: Dec 2004
Location: Bangalore India
Yes, the PCB layout is same as other 5 amps. I checked closely for solder shorting, discontinouty and did not find any.
Need to know what actually can cause the chip to heat up so fast.
__________________
Regards,
Din
  Reply With Quote
Old 30th January 2007, 01:03 PM   #4
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
Default Re: LM3886 - getting hot - low volume

Quote:
Originally posted by diarav
1) What is the first area / component to check/replace as the possible cause for this problem.
2) is my LM3886 chip possible damaged? I am still getting an output.
Before replacing anything answer a couple of questions.

When you tested the amps did you have a source connected to the input? If not, was the input left open while you were testing? Have you tried shorting the input to ground to see if the chip still gets really hot?

Did you use a load on the output while testing?

If you can't find any errors in your wiring or construction then there is a problem with one or more parts. Check the polarity of electrolytic caps to make sure they're installed properly. Snoop around with a multimeter and see if you can find any unusual voltages. Are the supply rail voltages at the chip's pin correct? What is the DC offset at the output of the bad amp? Things like that.
__________________
Brian
  Reply With Quote
Old 30th January 2007, 02:29 PM   #5
diarav is offline diarav  India
diyAudio Member
 
Join Date: Dec 2004
Location: Bangalore India
Thanks for the response Brian.

Chip gets hot even if input is open or connected - never tried shorting to ground.

Output was connected to 16ohms speaker.

Caps are connected with correct polarity.

Ah I did not check supply voltages? Perhaps will.

Question:
To check DC offset at output, does one short the input to the ground or leave it open?

Also I have currently disassembled the amp from my casing as I need to work on my casing, so it may be a while before I reassemble and test and post my results.
__________________
Regards,
Din
  Reply With Quote
Old 30th January 2007, 03:56 PM   #6
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
Quote:
Originally posted by diarav
To check DC offset at output, does one short the input to the ground or leave it open?
Short the input to ground when measuring DC offset at the output.
__________________
Brian
  Reply With Quote
Old 22nd May 2007, 11:14 AM   #7
diyAudio Member
 
Join Date: Mar 2007
Dear Diarav,

Did you solve the issue? Was it oscillating? just curious.

Regards
  Reply With Quote
Old 25th May 2007, 01:16 PM   #8
sukyone is offline sukyone  Thailand
diyAudio Member
 
sukyone's Avatar
 
Join Date: Jul 2006
Location: Bangkok
Send a message via AIM to sukyone Send a message via MSN to sukyone Send a message via Skype™ to sukyone
Your Lm3886 Chip are LM3886T Or LM3886TF?
if LM3886T please Check TAB of chip is not connect to ground.
__________________
My new Web.http://www.tumlaetong.com
  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
Volume control on DVD player remote. Lose resolution at low volume? Circlotron Digital Source 2 10th June 2011 07:20 PM
Gainclone LM3886 volume is abnormally weak kubark42 Chip Amps 7 5th June 2009 11:28 AM
lm3886 psu ponsonbybritt Chip Amps 10 13th January 2007 02:43 PM
Are two separate lm3886 = 2*lm3886 in parallel or bridge mode rs1026 Chip Amps 11 21st October 2004 10:24 AM
6*lm3886 Bpa Tim__x Chip Amps 1 15th August 2004 04:45 AM


New To Site? Need Help?

All times are GMT. The time now is 02:25 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