Help lowering noise in big series pass regulator circuit - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 10th October 2015, 04:38 AM   #1
diyAudio Member
 
Join Date: Oct 2014
Default Help lowering noise in big series pass regulator circuit

I've got a big linear power supply from the 70's here and I'm having trouble lowering the noise floor with it. I'm getting almost equal peaks at 60, 120, and 240 hertz. So far, I've replaced all of the caps and a few transistors in it. I've also replaced two op-amps for peace of mind. Right now, I'm at about -55dbV on the audio outputs of the synthesizer this thing belongs to. I've seen this power supply design perform at -65dbV before so I know that improvement is possible. I'm thinking about changing the integrator caps to quiet it down but can't figure out how to comprehend the equation that I found or if damping is even the problem. Here's the paper that I'm using as a guide: http://www.calex.com/pdf/3power_impedance.pdf The power supply diagrams are in the attachments.
Attached Images
File Type: jpg 59 - SVU Circuit Diagram.jpg (477.6 KB, 97 views)
File Type: jpg 60 - SVU Circuit Board & Wiring.jpg (425.2 KB, 96 views)
  Reply With Quote
Old 10th October 2015, 10:04 AM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Check the DC voltage across C730 and C731.

If your meter can (not all DMM can do this) measure AC voltage in the presence of a DC offset, then also measure the AC voltage across these two capacitors.
__________________
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote
Old 11th October 2015, 02:57 AM   #3
diyAudio Member
 
Join Date: Oct 2014
I just tested it with my Tek 2465. I'm thinking I've got a ground loop somewhere that is bleeding into my system. On the output of each rail, I'm getting about 5mv of ripple when connected to power supply ground. When connected to chassis ground, it jumps up to about 40mv.
  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
Lenard's Series Pass MOSFET Tube Regulator Qs ITPhoenix Power Supplies 4 19th April 2013 09:34 PM
In a series pass voltage regulator, where should the fuse be placed? Fusion916 Solid State 8 10th January 2013 07:45 PM
How big difference of noise between the realistic circuit and pspice simulation? goodnight521 Parts 1 20th June 2008 12:58 PM
How big difference of noise between the realistic circuit and pspice simulation? goodnight521 Analog Line Level 4 19th June 2008 06:22 PM


New To Site? Need Help?

All times are GMT. The time now is 10:37 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki