LM3875 power supply question. - 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 26th March 2011, 08:02 PM   #1
hotscot is offline hotscot  Scotland
diyAudio Member
 
Join Date: Aug 2004
Location: California
Default LM3875 power supply question.

I'm only getting @ 17 V DC when I'm expecting @ 37 V.

Does this suggest one of my diodes has failed?

I have a multimeter but find testing diodes tricky.

Thanks
Alan
  Reply With Quote
Old 26th March 2011, 08:09 PM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Plug your transformer in via a bulb tester and tell us what the bulb filament has done/is doing.
__________________
regards Andrew T.
  Reply With Quote
Old 26th March 2011, 08:14 PM   #3
diyAudio Member
 
Join Date: May 2008
Depending on your multimeter there are two ways of testing. Both require you to test the diode twice, once in forward and once in reverse direction. Some meters come with a diode test facility that shows the forward voltage in one direction and should show overload in the other. If your meter does not have that, use the impedance measurement. You should get overload in one direction and a low value in the other.
Diodes that show continuity (or forward voltage) in both directions or show overload in both directions are broken.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 26th March 2011, 08:27 PM   #4
hotscot is offline hotscot  Scotland
diyAudio Member
 
Join Date: Aug 2004
Location: California
Default Thanks for the input.

Found a dodgy diode with multimeter.
Now replacing.

Cheers
  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
Power supply question EL34Dave Tubes / Valves 5 5th January 2011 02:25 AM
LM3875 chipamp board incl power supply lgreen Swap Meet 1 11th December 2009 06:23 PM
Power Supply Question Captn Dave Tubes / Valves 14 3rd October 2008 07:20 PM
LM3875 power supply questions... nycavsr2000 Chip Amps 3 11th October 2006 05:42 PM
Power Supply Question Adam M. Chip Amps 1 25th February 2004 03:29 AM


New To Site? Need Help?

All times are GMT. The time now is 10:25 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