Lightspeed Attenuator a new passive preamp - Page 285 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 December 2009, 06:59 PM   #2841
diyAudio Member
 
Tripmaster's Avatar
 
Join Date: Feb 2008
Location: UK
Quote:
Originally Posted by AndrewT View Post
what is the voltage with the circuit disconnected, i.e. no LED and no LDRs.
When I applied power it peaked at 15v and after 30 seconds the voltage settled at 14.92v
__________________
Richard
My photostream: http://www.flickr.com/photos/59839778@N04/
  Reply With Quote
Old 23rd December 2009, 07:55 PM   #2842
Puffin is offline Puffin  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: U.K
Tripmaster and I discussed this problem. We wondered whether it could be reverse voltage. Would a diode on the 7805 be worth doing in any event?
  Reply With Quote
Old 23rd December 2009, 08:19 PM   #2843
diyAudio Member
 
Tripmaster's Avatar
 
Join Date: Feb 2008
Location: UK
Quote:
Originally Posted by Puffin View Post
Tripmaster and I discussed this problem. We wondered whether it could be reverse voltage. Would a diode on the 7805 be worth doing in any event?
Yes. Ive just added a diode to the LED
__________________
Richard
My photostream: http://www.flickr.com/photos/59839778@N04/
  Reply With Quote
Old 23rd December 2009, 08:22 PM   #2844
Puffin is offline Puffin  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: U.K
Does that do the same thing as across the 7805?
  Reply With Quote
Old 23rd December 2009, 09:53 PM   #2845
diyAudio Member
 
Tripmaster's Avatar
 
Join Date: Feb 2008
Location: UK
Quote:
Originally Posted by Puffin View Post
Does that do the same thing as across the 7805?
No
__________________
Richard
My photostream: http://www.flickr.com/photos/59839778@N04/
  Reply With Quote
Old 24th December 2009, 07:25 AM   #2846
Puffin is offline Puffin  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: U.K
  Reply With Quote
Old 24th December 2009, 11:34 AM   #2847
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
15V at the smoothing cap with no load.
drops to 14.45V with the LDRs drawing current.
drops to 13.87V with the single LED added.

You need proper smoothing cap across the rectified supply.
Try 1000uF or somewhere close, 470uF to 2200uF.

Measure those three conditions again.
__________________
regards Andrew T.
  Reply With Quote
Old 24th December 2009, 11:50 AM   #2848
diyAudio Member
 
Tripmaster's Avatar
 
Join Date: Feb 2008
Location: UK
Quote:
Originally Posted by AndrewT View Post
15V at the smoothing cap with no load.
drops to 14.45V with the LDRs drawing current.
drops to 13.87V with the single LED added.

You need proper smoothing cap across the rectified supply.
Try 1000uF or somewhere close, 470uF to 2200uF.

Measure those three conditions again.
Hi Andrew

I'm keeping you busy!

Should I place this cap before the regulator, just after the green terminal block?
__________________
Richard
My photostream: http://www.flickr.com/photos/59839778@N04/
  Reply With Quote
Old 24th December 2009, 12:09 PM   #2849
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
yes, locate the smoothing right after the power input terminals.
__________________
regards Andrew T.
  Reply With Quote
Old 24th December 2009, 12:25 PM   #2850
Puffin is offline Puffin  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: U.K
I use 1,000uf either side of the reg.

[IMG][img=http://img15.imageshack.us/img15/686/daveslspeednd008.th.jpg][/IMG]
  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



New To Site? Need Help?

All times are GMT. The time now is 03:01 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