LM3886 issues - Page 3 - 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 23rd June 2010, 10:47 AM   #21
diyAudio Member
 
Join Date: Nov 2005
Location: Ohio
Ok, with the DMM in diode test mode I get 1.446 when connecting the positive lead to the neg leg and the neg lead to the pos leg. If I connect the pos lead to to the neg leg and then connect the neg lead to either of the center legs I get about half that reading. If I reverse the leads I get no reading. Does this seem backwards? Shouldn't the pos be connected to the positive rail and the neg to the neg? Or is this correct? If in fact the rectifier is good then I don't understand how it got so hot.
  Reply With Quote
Old 23rd June 2010, 04:06 PM   #22
diyAudio Member
 
Join Date: Nov 2005
Location: Ohio
Well.... I plugged it in and was testing and I think I may of messed it up more. My lead slipped and shorted out 2 connections and now I don't seem to be getting much voltage. Thinking maybe the transformers are messed up. What I get for working on it with my kids hovering. Not sure how I'm going to pull that out and test them. Tried pulling the old rectifier out and don't think it's coming out lol.
  Reply With Quote
Old 23rd June 2010, 06:10 PM   #23
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
The transformers may have survived as long as you didn't keep power on for long (i.e. less than 10 seconds). You probably just blew the recitifiers.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 24th June 2010, 04:11 AM   #24
diyAudio Member
 
Join Date: Nov 2005
Location: Ohio
Well, it wasn't shorted for 10 seconds no....but it may of been on. I have one o the transformers removed so far..... whoever decided to glue all this stuff in is an a**hole.... Anyways what's the best way to test a transformer?
  Reply With Quote
Old 24th June 2010, 04:41 AM   #25
BudP is offline BudP  United States
diyAudio Member
 
BudP's Avatar
 
Join Date: Feb 2007
Location: upper left crust, united snakes
The transformer on the left appears to have a very messy and disturbed lead out. I cannot tell if the leads them selves are discolored and if the tape that wraps the toroid windings is discolored. I do notice that the transformer on the right has it's mounting glue intact and the one on the left appears to have lost that smooth glue coating. Am I being deceived by the picture or are these actual differences?

As for transformer testing, a simple ohms check, which if closely similar between known good and suspect channels, should be followed with a power on, no load check of voltages, which should be followed with a loaded check of voltages. The load should be at least from a 5 watt resistor and follow ohms law for R = E/I to obtain a proper size for the resistor.

It is quite possible that a semi blown regulator has overstressed one of the transformers and shorted the wires at the connection point, where toroid's are the most susceptible.

Bud
__________________
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
  Reply With Quote
Old 24th June 2010, 04:48 AM   #26
diyAudio Member
 
Join Date: Nov 2005
Location: Ohio
The one on the right is actually the bad channel, something heated up there and melted the glue so it smoothed out. I have both transformers out, I'm not sure what to do with this darn thing all this glue is really ticking me off lol. Thinking of just getting a bigger 21VAC transformer and running both amps off one instead of the dual mono setup. And then obviously a new case because this setup is just crazy.

I'll try testing the transformers later for now I'm tired of messing with it. Took me an hour just to remove them. I can't even get the rectifiers out.
  Reply With Quote
Old 24th June 2010, 05:18 PM   #27
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Check the amps as posted earlier before you use more time and effort with the power supply. Can you power the suspect amp with the known good power supply and vice-versa?
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 25th June 2010, 03:21 PM   #28
diyAudio Member
 
Join Date: Nov 2005
Location: Ohio
Well I tested them with a DMM as suggested and they behaved as they should. At this point neither channel are working and pretty sure it's the rectifiers or the transformers....possibly both?
  Reply With Quote
Old 25th June 2010, 04:56 PM   #29
Arx is offline Arx  Canada
diyAudio Member
 
Join Date: Aug 2003
Location: North Vancouver, B.C.
Quote:
Originally Posted by Dougie085 View Post
Well I tested them with a DMM as suggested and they behaved as they should. At this point neither channel are working and pretty sure it's the rectifiers or the transformers....possibly both?
disconnect the power supplies from the chips, and check their voltages.

Linear supplies are pretty simple, usually they either work or they don't.
  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
LME49810/11/30, LM3886 hum issues & grounding tomchr Chip Amps 10 22nd February 2010 10:18 PM
PA100 Heat Issues...LM3886 Based..Any Ideas? MartyM Chip Amps 10 16th December 2007 11:18 PM
LM4780 (LM3886) impedance issues Alfetta87 Chip Amps 1 21st November 2006 02:35 PM
LM3886 & PGA2310 issues Xlrator Chip Amps 0 7th March 2006 07:25 AM
Are two separate lm3886 = 2*lm3886 in parallel or bridge mode rs1026 Chip Amps 11 21st October 2004 10:24 AM


New To Site? Need Help?

All times are GMT. The time now is 12:35 PM.


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