Need help with a F5 PSU mistake - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 22nd May 2011, 09:00 PM   #11
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
anlive, you have gotten bad advice here. You should mirror the negative part. The resistors must be at the bottom but the PSU will still work but not as intended.

Power Amp PSU Board (for e.g. LYNX Amp)
Send me a message if you want to take a look at the schematics, too large to be uploaded.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 23rd May 2011, 02:28 AM   #12
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by peranders View Post
anlive, you have gotten bad advice here. You should mirror the negative part. The resistors must be at the bottom but the PSU will still work but not as intended.

Power Amp PSU Board (for e.g. LYNX Amp)
Send me a message if you want to take a look at the schematics, too large to be uploaded.
Thanks. I know what you mean. NPs schematic also has a mirrored CCRCC network for each leg of the PSU.

Having committed the error in my PCB, I am trying to find out the impact if at all there is any. The cost of correcting the PCB is cutting the tracks and hardwiring them right or desoldering all the electrolytic.

I buy the AC hum theory and that is should not impact in which leg the RC network is. What is the logic in your view?

Cheers.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 23rd May 2011, 04:26 AM   #13
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
You PS will get unsymmetrical with this equivalent circuit. Notice that the negative half will be unfiltered plus two caps doing nothing.
Attached Images
File Type: jpg bild.JPG (20.1 KB, 127 views)
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 23rd May 2011, 06:43 AM   #14
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by peranders View Post
You PS will get unsymmetrical with this equivalent circuit. Notice that the negative half will be unfiltered plus two caps doing nothing.
Please refer to the schematic posted by me earlier. They are two separate but identical DC power supplies employing RC filter but connected at the outputs with -ve of one supply and +ve of another supply to make a 0v reference for a +,0,- power supply.

I cannot figure out in what way the RC filter of the bottom rail becomes ineffective. My knowledge is definitely limited and would like to be corrected. Your schematic looks very different from mine.

Cheers.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 23rd May 2011, 09:48 AM   #15
cnpope is offline cnpope  United States
diyAudio Member
 
Join Date: Aug 2009
Location: College Station, TX
As long as you do exactly what is shown in drazen's schematic, then everything will be fine. This means modifying your existing schematic, to break the link between W2 and W3 that is shown in your schematic. i.e., the two supplies should be connected only by the link between W6 and W7.

If you stick with your schematic in unmodified form, then peranders's equivalent schematic is exactly right, and, as he says, this is not what you want.

Chris
  Reply With Quote
Old 23rd May 2011, 10:24 AM   #16
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
You must break/cut the connection at the input just as D has shown.

The two supplies are isolated. They will both filter and give DC with a tiny rounded sawtooth superimposed. The +ve sawtooth should be rounded, I don't know if the -ve will be rounded, or inverted & rounded.

In my understanding, connecting at the output does not change the DC quality of either supply.

I have never done it this way, but you can easily measure the finished PSU (no amplifier/s) to check if both polarities have the same ripple. Do this using a bulb tester first and then direct on line.
__________________
regards Andrew T.
  Reply With Quote
Old 23rd May 2011, 10:54 AM   #17
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by cnpope View Post
As long as you do exactly what is shown in drazen's schematic, then everything will be fine. This means modifying your existing schematic, to break the link between W2 and W3 that is shown in your schematic. i.e., the two supplies should be connected only by the link between W6 and W7.

If you stick with your schematic in unmodified form, then peranders's equivalent schematic is exactly right, and, as he says, this is not what you want.

Chris
Quote:
Originally Posted by AndrewT View Post
You must break/cut the connection at the input just as D has shown.

The two supplies are isolated. They will both filter and give DC with a tiny rounded sawtooth superimposed. The +ve sawtooth should be rounded, I don't know if the -ve will be rounded, or inverted & rounded.

In my understanding, connecting at the output does not change the DC quality of either supply.

I have never done it this way, but you can easily measure the finished PSU (no amplifier/s) to check if both polarities have the same ripple. Do this using a bulb tester first and then direct on line.
Thanks everyone. My mistake. I have not connected W2 & W3 together as I have indicated in my original schematic but followed drazen's schematic.

I have checked AC ripple at the outputs and my Fluke DMM cannot detect any AC outputs.

Finally connected to the amp and works well. No hum.

Cheers.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 23rd May 2011, 11:28 AM   #18
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by anilva View Post
Thanks everyone. My mistake. I have not connected W2 & W3 together as I have indicated in my original schematic but followed drazen's schematic.

I have checked AC ripple at the outputs and my Fluke DMM cannot detect any AC outputs.

Finally connected to the amp and works well. No hum.

Cheers.
Correction: I measured AC ripple at the PS output. Both rails measure around 35mV of AC, whereas at bridge rectifier, the ripple measures 450mV of AC. There seems to be nearly 1/10th reduction of ripple across the RC network.

The caps are hot (my guess around 35-40 degrees centigrade) and the resistors are quite hot 50-60 degrees centigrade, when the power is being drawn by the amp.
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 23rd May 2011, 12:05 PM   #19
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Improve the ventilation around the capacitors. You must do everything you can to keep them cool. Even adding extra C if necessary. Try replacing the first 22mF C with ten 2m2F Cs in parallel. Use the 22mF as an extra final C
__________________
regards Andrew T.
  Reply With Quote
Old 23rd May 2011, 12:07 PM   #20
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by anilva View Post
I have checked AC ripple at the outputs and my Fluke DMM cannot detect any AC outputs.
I was about to tell you to buy a new (cheap) DMM, but post18 explained.
__________________
regards Andrew 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
F5 PSU Fuse drcg Pass Labs 0 18th April 2011 11:55 AM
FS: Cviller F5 P.C.B with PSU bchristmas Swap Meet 1 11th September 2010 02:16 AM
FS : Peter DANIEL PCB F5 + PSU korben69 Swap Meet 6 10th September 2010 12:47 PM
F5 psu layout OliG Power Supplies 5 2nd April 2010 10:52 PM
Bpa300, f5, psu, lm4780 for sale chatziva Swap Meet 16 5th October 2009 08:37 PM


New To Site? Need Help?

All times are GMT. The time now is 12:51 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