GFA-535: Looking for troubleshooting help - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 2nd May 2013, 12:19 AM   #1
diyAudio Member
 
lancer7703's Avatar
 
Join Date: Nov 2012
Location: SoCal
Default GFA-535: Looking for troubleshooting help

Hello all,
Let me preface by saying that this is the first amp I've really had a chance to get my hands dirty with; I've only got into audio since I graduated college.

I had just finished replacing most of the old caps and the amp was sounding great. DC offset was about 20 mV on both channels, which, as I understand it, isn't horrible. Everything else checked out.

The problem came as I was adjusting the bias. I wasn't using any clips (lesson learned ), and my roommate burst into my room, scaring the living hell out of me. Well, the probe slipped out of my hand as I jumped a foot and contacted something on the amp board. Both fuses blew, naturally.

I can replace the fuses, but B- continually blows. Seems like the B+ fuse holds just fine. I have a schematic; anybody have any recommendations on where to start? Could it be that the transistor was toasted? Is this really vague?

Thank you!
  Reply With Quote
Old 2nd May 2013, 02:08 AM   #2
diyAudio Member
 
sakellogg's Avatar
 
Join Date: Nov 2008
Location: dixon ill
i would pull the transistors one by one and test.

i'd start with the ones in the bias cir first.
if you post a copy of the scematic it might help.
__________________
I'm not crazy, my mother had me tested
  Reply With Quote
Old 2nd May 2013, 04:37 AM   #3
diyAudio Member
 
lancer7703's Avatar
 
Join Date: Nov 2012
Location: SoCal
Here's what I have for the schematic. I have a very vague idea of how everything is coming together, so again, any suggestions would be much appreciated!

If it does turn out to be that the transistors are shot, does anyone have a good source for replacements? I've seen lots of 'generics' on the Bay and such, but is that one of those cases where it shouldn't be trusted?
Attached Images
File Type: jpg GFA-535 schematic.JPG (621.3 KB, 42 views)
  Reply With Quote
Old 2nd May 2013, 06:08 AM   #4
Leolabs is offline Leolabs  Malaysia
diyAudio Member
 
Leolabs's Avatar
 
Join Date: Dec 2004
Location: Bukit Mertajam
Send a message via MSN to Leolabs
Check those high power transistors first,esp the output stage....

For the transistors,many no longer produce by original factory but still available through KEC or Fairchild.
  Reply With Quote
Old 3rd May 2013, 05:57 PM   #5
diyAudio Member
 
lancer7703's Avatar
 
Join Date: Nov 2012
Location: SoCal
Thanks for the help! After checking, the transistors appear to be shot.

I've been to both of those sites before, but never for transistors; I'll check it out!
  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
Adcom GFA-535 Transistor sub Ardvaark Solid State 3 6th September 2011 01:41 AM
Adcom GFA-535 Settings Ardvaark Solid State 2 16th August 2009 08:10 PM
GFA-535 Manual Funkenstein Solid State 6 16th June 2009 01:26 AM
FS: Adcom GFA-535 sdstarnes Swap Meet 3 12th February 2008 02:43 AM
GFA 535 right channel out. sdstarnes Solid State 8 4th February 2008 03:07 AM


New To Site? Need Help?

All times are GMT. The time now is 11:40 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