Another GFA-555 With high dc offset - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 21st July 2010, 04:21 AM   #1
diyAudio Member
Join Date: May 2010
Location: Florida
Default Another GFA-555 With high dc offset

I am at a loss right now as to why I have such high dc offset at the output of my GFA-555 (not a MKII). One channel the right has 22.7mv and the left has 268.4mv. I rechecked the BIAS and have it set at -16mv as per the service manual. I have checked everything on the input board and everything appears to be fine. The amp sounds fine other than just the high channel sounds a little distorted. Has anyone had this problem before with this amp? I did check all the outputs and all appear fine and have never been replaced. Pre-drivers fine also, at least they appear fine no shorts, open or high resistance. I,m driving a pair of Snell's and hate to see them smoke. I have one GFA-555 and one GFA-555 MKII Bi-amp'ed. I also noticed that the BIOS current is not stable it moves from 16mv-18mvand dosn as low as 10mv. The current across the outouts are not all the same either and range from 21mv~18mv. Could this be the outputs in that ch are going bad even though the messure fine?
  Reply With Quote
Old 21st July 2010, 05:50 AM   #2
diyAudio Member
Join Date: May 2010
Location: Florida
I see this I may have put this in the wrong forum. I should have put this in Solid State, mod could move if needed.
  Reply With Quote
Old 22nd July 2010, 12:51 AM   #3
llwhtt is online now llwhtt  United States
diyAudio Member
Join Date: Jun 2008
Location: SoCal
I wonder if this particular model has the dreaded leaky capacitor disease? I think DC offset was the first problem to show up. Check the circuit boards for evidence of electrolyte around the capacitors. Anatech (Chris) on this forum is the one you need to get in touch with. He was a Adcom servicer in Canada. He can fill you in on everything that needs to be done if that is the case.

  Reply With Quote


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
Another high DC Adcom GFA-555 fredlf Solid State 666 31st January 2017 09:11 PM
Adcom GFA-555 mk2 left slight cracking in high freq lga775 Solid State 2 4th December 2010 11:30 AM
Help! Adcom GFA 585 DC High offset problem birdyman Solid State 2 29th April 2010 01:44 PM
Adcom GFA-555 Feedback DC-Blocking Cap? EchoWars Pass Labs 14 14th April 2010 07:12 PM
Adcom GFA-555II with DC Offset sjdemark Solid State 19 28th February 2009 01:33 PM

New To Site? Need Help?

All times are GMT. The time now is 07:42 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2