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 14th June 2010, 12:54 AM   #1
diyAudio Member
 
Join Date: Feb 2009
Default Sony TA-AX380 Stopped Working

I am relatively new to the forums and apologize if this is not the right place to ask for help - I figured a DIY audio forum would be the best place to look for amplifier repair.

Anyway, I bought this amplifier two days ago - it worked perfectly when I first received it. After leaving the unit on over night with no music playing, I found the power indicator light to be "off". The receiver does not play audio now. If I turn the volume up all the way I do not hear any hum at all. I opened the case and cannot see anything burnt, fuse tested to have ~0 ohms resistance. When I power on the unit the relays fire, the transformer hums slightly (is energized). I really have no clue at all what it could be and it is driving me nuts.

This unit was actually purchased to replace another Sony receiver I had that "melted down" due to my own abuse. That unit similarly did not show any signs of burnt components or failed fuses. Maybe if I am lucky both of these can be fixed. What is peculiar to me is that this receiver failed with no load on it.

Could the transformers be going bad somehow?

Thank you!
  Reply With Quote
Old 14th June 2010, 01:28 AM   #2
diyAudio Member
 
Join Date: Feb 2009
This is an old 1980's amp by the way, just to be clear.
  Reply With Quote
Old 14th June 2010, 06:46 AM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
One thing to check first is that both units are rated for your mains supply voltage... if they are adjustable are they set correctly ?

You really need a circuit...

however faultfinding at a very basic level means measuring the main rail voltages (across the big caps in the PSU) and seeing if the output devices are supplied with voltage (discrete or power IC ?)

A good clue has to be the power light... trace it back... what feeds it. Look for low voltage regulators... if the amp has remote control there will be a 5 volt rail... is there 5 volts on the remote receiver etc.

Transformers fail through overheating... very unlikely, and usually there is a thermal fuse buried in the primary winding. If it buzzes and fire the relay it's not that.

Pictures ?????
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 14th June 2010, 08:16 AM   #4
diyAudio Member
 
Join Date: Feb 2009
Thanks for the response! The amplifier is only rated for 120V which is the correct voltage, it is not adjustable.

Where would these main rail/big caps in the PSU be... here is the main board below as well as the auxiliary board.

Click the image to open in full size.

Click the image to open in full size.

I will check what powers the light tomorrow morning. I notice that on the header to the front panel there is a +5v, +9v, and -9v marked. Maybe I should start there. I believe it is a discrete amplifier, how do I check?

Thank you!

Here are the direct picture links so you can read the circuit board...

http://img.photobucket.com/albums/v4...s/IMG_1571.jpg
http://img.photobucket.com/albums/v4...s/IMG_1566.jpg
  Reply With Quote
Old 14th June 2010, 08:43 AM   #5
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
This is a discrete amp as you can see 4 large power transistors (they probably have Sanken or SK written on em, right?).

The main filter capacitors are those two black cylinders at the top of the first picture. They could probably do with replacement, although that's a later job after you've found the first fault.

Checking if those 5v and 9v voltages are present is a good start. I'd lay good money that one of them isnt.
  Reply With Quote
Old 14th June 2010, 08:49 AM   #6
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by jaycee View Post
This is a discrete amp as you can see 4 large power transistors (they probably have Sanken or SK written on em, right?).

The main filter capacitors are those two black cylinders at the top of the first picture. They could probably do with replacement, although that's a later job after you've found the first fault.

Checking if those 5v and 9v voltages are present is a good start. I'd lay good money that one of them isnt.
Will check. Yes Sanken.

I have noticed now that the power indicator light glows ever so slightly - so it must be receiving some current. When the muting button is pressed, the light vanishes entirely. Just food for thought... probably very low voltage.
  Reply With Quote
Old 14th June 2010, 10:13 AM   #7
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
the specific amp features an stand by circuit ( see the small trafo next to the big one ) you need to carefully check how voltages a runing arround various circuits ( caution there is needed since there is dangeroius voltages related ) to find out if both of traffos are suplied

the click you may hear on start up might be the stand by relay but after that you need to listen to the click that comes from the protection relay

sorry to say that this cannot be trouble shooted by any one without any expirience ....
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 14th June 2010, 10:17 AM   #8
diyAudio Member
 
Join Date: Feb 2009
There are two clicks, first the power switch - second the switch on the main board pictured above. I will see if I can check for power to the smaller transformer. What does the stand by circuit do? Thanks!
  Reply With Quote
Old 14th June 2010, 10:31 AM   #9
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
hmmm that is good then you should focus on the secondary power supply that give the 5 and 9 volt

a comon failure for this type of amps is the input selector IC
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 14th June 2010, 10:36 AM   #10
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by sakis View Post
hmmm that is good then you should focus on the secondary power supply that give the 5 and 9 volt

a comon failure for this type of amps is the input selector IC
You are referring to the smaller transformer? I will trace back the 9v and 5v source tomorrow. Is that 5/9v source signal or is it something else that merely lets you know if power is running through specific stages?
  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
Amp Stopped Working twhittle14 Car Audio 30 25th November 2012 04:33 PM
Rotel RCD-855 stopped working Mr DNA Digital Source 5 26th November 2009 07:26 PM
el84 1 channel stopped working help eddiedavies Tubes / Valves 5 2nd April 2007 11:32 AM
HELP! My remote volume control stopped working! :( paulspencer Analog Line Level 14 15th October 2006 04:34 AM
pinnacle 850 stopped working jamesj2 Multi-Way 1 14th February 2005 09:48 AM


New To Site? Need Help?

All times are GMT. The time now is 01:28 AM.


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