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.

Rail voltage imbalance.
Rail voltage imbalance.
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 26th June 2011, 10:54 PM   #1
pjblakey is offline pjblakey  United States
diyAudio Member
Join Date: Mar 2009
Location: Smoky Mountains, NC
Default Rail voltage imbalance.

I have put together an F5 type amp using a tubeshunter kit.
I checked the power supply with no amps connected and the rectifier and output voltages remained stable at +/_ 26VDC for 30 minutes. I am using an Avel 250VA 18+18 transformer.
When I connected the left channel, the rail voltages immediately began to drift upwards on the negative side with the bias pots at 0 ohms(or close). The voltage peaks at close to -46VDC and +6VDC.
Right channel ditto.
I have checked the mica insulators, made sure of amp ground to PSU, looked for broken tracks and dry solder joints.
Before I realized this was happening, I did manage to adjust the bias current to !.3amps, but the amp shut down. No blown fuses. either 1 amp or 2.5amp fast blow.
Has anyone had a similar experience or any bright ideas?


  Reply With Quote
Old 26th June 2011, 11:23 PM   #2
semi932 is offline semi932  United States
diyAudio Member
semi932's Avatar
Join Date: Nov 2009
Definitely something in the boards as you say the voltage is ok coming out of rectifier and caps.

Check and make sure fet's are installed correctly for starters.

Also the ztx transistors are oriented correctly.
  Reply With Quote
Old 27th June 2011, 01:17 PM   #3
Bill Fuss is offline Bill Fuss  United States
Join Date: Oct 2005
Location: Central Florida
I hope you didn't expect a lot of help, seeing that you are using pirated Chinese boards.
  Reply With Quote
Old 27th June 2011, 01:39 PM   #4
Andy5112405 is offline Andy5112405  United Kingdom
Join Date: Nov 2006
Location: Torpoint
Try loading the PSU with resistors just to check that everything is OK.
  Reply With Quote
Old 27th June 2011, 06:43 PM   #5
h_a is offline h_a  Europe
diyAudio Member
h_a's Avatar
Join Date: Sep 2006
Location: Graz, Austria
Ground of +-rail and --rail connected to eachother and connected to safety ground? (Sounds like a floating ground to me).

High Octane phono preamp Wiki
  Reply With Quote
Old 27th June 2011, 10:03 PM   #6
pjblakey is offline pjblakey  United States
diyAudio Member
Join Date: Mar 2009
Location: Smoky Mountains, NC
Thank you for the responses.
After further inspection of the solder joints and component orientation and functioning, I'm pretty sure that it is a grounding issue. Have to check when I return from vacation.

  Reply With Quote


Rail voltage imbalance.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
F5 loaded rail-to-rail voltage? CanAm Man Pass Labs 40 20th March 2011 08:43 PM
Rail voltage ggetzoff Pass Labs 0 23rd March 2010 11:54 PM
Rail voltage bass junkie Car Audio 2 17th January 2010 03:25 AM
Rail Voltage to Capacitor Voltage Mermprin Parts 6 20th September 2004 04:56 PM
Rail voltage compared to transformer voltage SteveG Solid State 4 23rd July 2002 12:50 AM

New To Site? Need Help?

All times are GMT. The time now is 10:40 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio