Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Beginner's Gainclone, HiFi LM1875, The Amplifier Board
Beginner's Gainclone, HiFi LM1875, The Amplifier Board
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 7th July 2013, 04:27 PM   #281
ashok is offline ashok
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
Beginner's Gainclone, HiFi LM1875, The Amplifier Board
ServoG: how does the amp sound? ( assuming you have good speakers and source !)
If it doesn't sound GREAT then you've done something wrong I guess !
For it's limited power and price it sounds really great.
You said " .....played well....". That isn't the same as "GREAT" !
__________________
AM
  Reply With Quote
Old 7th July 2013, 04:36 PM   #282
servoG is offline servoG
diyAudio Member
 
Join Date: Jun 2013
@ Ashok
6 hours of continuous music since I fix it... You are right... For it's limited power and price it sounds really great...:-)
  Reply With Quote
Old 10th July 2013, 09:09 AM   #283
danielwritesbac is offline danielwritesbac  United States
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Hey, this is all good news. I like it!
On the power question, maybe this will help:
Speakers are the output, and decibels are far louder than watts.
__________________
DIY Models & AppsClipNipperLM1875TDA7293Powerful Parallel TDA7293 kit ♦ My post has opinion.
  Reply With Quote
Old 15th July 2013, 12:33 AM   #284
prezden is offline prezden  Canada
diyAudio Member
 
Join Date: Nov 2008
Hey Daniel
I need you help again- it seems I have screwed one of the boards up again
After installing the pots one channel is working good. The other doesn't do anything at a lower volume and crackles really loudly when I turn it up. The music is playing. When it first happened I thought it was the pot so I took it off. The noise was the same. Then I put the pot back on- same thing.
I have looked at this thing for hours comparing it to the one that works as well as this pictures you posted but I can't see anything. The circuit checks out ok. Power at the amp is 24.75 with 0 dc offset at the speaker. I've tried 3 different speakers but it's always the same noise.

sincerely baffled - prezden
Attached Images
File Type: jpg 1875 front.jpg (592.2 KB, 461 views)
File Type: jpg 1875 back.jpg (638.8 KB, 419 views)
  Reply With Quote
Old 15th July 2013, 01:15 AM   #285
danielwritesbac is offline danielwritesbac  United States
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Well, I've stared at it for a good half hour and didn't see anything. But I could not quite identify all of the connections near the little red and blue caps. So, I've got to ask, if you measure between 0v and Pin1 with your ohmmeter, does it do 10K or. . . something else?
__________________
DIY Models & AppsClipNipperLM1875TDA7293Powerful Parallel TDA7293 kit ♦ My post has opinion.
  Reply With Quote
Old 15th July 2013, 09:42 AM   #286
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
I suspect a broken connection, maybe at the input?
__________________
regards Andrew T.
  Reply With Quote
Old 15th July 2013, 04:46 PM   #287
prezden is offline prezden  Canada
diyAudio Member
 
Join Date: Nov 2008
Thank guys- In measuring between pin 1 and OV i get 9.9K.
I've looked at the board carefully with a magnifying glass and can't see any broken connections.
  Reply With Quote
Old 16th July 2013, 05:28 AM   #288
danielwritesbac is offline danielwritesbac  United States
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
The 9.9K is okay.

I see some solder quite close to the heatsink--we don't want it touching the heatsink.

Question:
Is the noise like a radio static crackle or is it like "flip, flip, flip, flip" sort of noise?
__________________
DIY Models & AppsClipNipperLM1875TDA7293Powerful Parallel TDA7293 kit ♦ My post has opinion.
  Reply With Quote
Old 16th July 2013, 09:13 PM   #289
prezden is offline prezden  Canada
diyAudio Member
 
Join Date: Nov 2008
Hi Daniel
I have uploaded a shot video to youtube so you can listen to what it sounds like. There is no solder on the heatsink.
Thanks for your help

1875 noise Computer - YouTube
  Reply With Quote
Old 18th July 2013, 01:41 AM   #290
danielwritesbac is offline danielwritesbac  United States
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
That wasn't the slow stead rhythm of the overload sound. Oh, much different!
Be sure to drain the power caps (by applying 50R resistors, not fingers) measure to assure the absence of voltage, and then make really good use of the ohmmeter to compare the board that works against the board that doesn't. Note: Don't modify the working amp board--Just measure it.
You might want to check the feedback and feedback-shunt resistors as well as the nfb-shunt cap and ground--trace around that whole area to see if it matches up with the other board.
If that's all good, then trace all over the input circuit to see if it matches up with the other board.
Next,
Re-heat all solder connections that are on the bad board. Check with some swapping resistors and caps to see if you can "move the problem" preferably away from the amp board--for example, the ohmmeter won't spot bad caps, but you can swap in some different caps, one at a time, to see if they work differently.
and then,
If you've eliminated all of the other possibilities, then a chip might be broken.
__________________
DIY Models & AppsClipNipperLM1875TDA7293Powerful Parallel TDA7293 kit ♦ My post has opinion.

Last edited by danielwritesbac; 18th July 2013 at 01:47 AM.
  Reply With Quote

Reply


Beginner's Gainclone, HiFi LM1875, The Amplifier BoardHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Beginner's Gainclone, Safety and, The Power Supply Board (please contribute) danielwritesbac Chip Amps 118 18th June 2008 06:12 PM
Beginner's Gainclone, LM3875, The Amplifier Board danielwritesbac Chip Amps 37 22nd May 2008 06:43 PM


New To Site? Need Help?

All times are GMT. The time now is 09:30 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki