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

Pass Labs This forum is dedicated to Pass Labs discussion.

F5 bias question
F5 bias question
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
Thread Tools Search this Thread
Old 4th March 2013, 08:08 AM   #11
Marra is offline Marra  United Kingdom
diyAudio Member
Join Date: Nov 2009
Location: Near Lincoln
F5 bias question
Don't just turn one pot you need to adjust them alternately by half a turn whilst monitoring the output and the voltage across R11 or R12.They interact a lot turning one alters the voltage over both resistors.
  Reply With Quote
Old 4th March 2013, 12:49 PM   #12
rade95 is offline rade95  United States
diyAudio Member
Join Date: Apr 2010
Location: Boulder, Colorado
Thats not the problem, I can go as slow as 1/2 turn each on P1 then P2, makes no difference. Something is bad, either P ch JFET or N ch MOSFET, I think.
UGS pre, stock F5, PassLabs X2.5, Aleph P
  Reply With Quote
Old 4th March 2013, 12:57 PM   #13
cviller is offline cviller  Canada
diyAudio Member
cviller's Avatar
Join Date: Dec 2005
Location: Toronto
Marre could still be right - depending on where your trimpot is on its scale, there can be a lot of turns without any noticable effect. Best is to nul both and try again. Alternatively, you can take some good pictures and post them - someone might be able to spot something.
If you really want help, you can print out the schematics, place your ground probe on ground and measure voltage around the bias areas, write it on the schem, scan it and share it here on the forum. Then all the smart guys here will be able to help you quickly.
  Reply With Quote


F5 bias questionHide 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
CCS bias question alexmoose Tubes / Valves 4 22nd July 2006 05:21 PM
Bias pot question Burnedfingers Tubes / Valves 1 1st January 2006 02:49 PM
A question of bias... DrG Tubes / Valves 30 28th August 2003 09:30 AM
a75 bias question SteveG Pass Labs 3 16th January 2002 11:06 PM

New To Site? Need Help?

All times are GMT. The time now is 06:53 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio