Sony STR-6065 Receiver Left Channel Issues - 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 3rd July 2011, 01:25 PM   #1
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
Unhappy Sony STR-6065 Receiver Left Channel Issues

Hi folks,
I have a Sony STR-6065 receiver that is in great shape except for one major problem: no audio from left channels. Both Main and Remote lefts are not working. When I turn on the receiver, I get an initial "pop" from the left channel speaker, then the right channel gradually comes on as you'd expect from a receiver.

There's 1 fuse and that's not related to the output of either channel. If that was blown, the unit wouldn't even turn on, so I know that's not the issue.

What I've done so far:
1. Checked all connections to speakers and channels
2. Swapped speakers/channels with no change in problem
3. Used Deoxit on all switches and pots.
4. Purchased the service manual and I feel the problem may be traced to the power amplification board. (This is just an assumption and reason why I'm asking for help).

So far, I haven't seen signs of bulging caps. What recommendation do any of you have? This is a real nice looking receiver with decent a decent following and I'd like her to rock again.
  Reply With Quote
Old 3rd July 2011, 06:26 PM   #2
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
Oops. I bet this topic is in the wrong section. Sorry, first post here...
  Reply With Quote
Old 3rd July 2011, 07:02 PM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Nope... it's in the right section

We'd have to see the circuit but most faults like this are caused by a power amp problem... either failed output transistors or a failed "STKxxxx" module if it uses those.

You need to check the DC offset at the L and R amplifier outputs (on the board before any protection relays) as a first step.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 4th July 2011, 11:22 PM   #4
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
Thanks for the tips Mooly ! I'll be studying that area more closely soon. Here's a segment of the power amp circuit :
Attached Images
File Type: jpg schem01.jpg (151.0 KB, 156 views)
  Reply With Quote
Old 5th July 2011, 06:32 AM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Check that the DC voltage on those two 0.5 ohm 5 watt resistors is zero on the faulty channel as measured from ground. Can't make the numbers out... they go to Q901 and 902

It should be essentially zero on each end of each resistor.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 5th July 2011, 03:25 PM   #6
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
Just checked the 0.5 resistors (R738, R739) this morning. Getting a 0.00 reading on both.
  Reply With Quote
Old 5th July 2011, 06:06 PM   #7
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
OK... so with the amp on you have zero volts DC on those 0.5 ohms. I'm surprised tbh, but that's a good result. In a way that means 95% that the problem is elsewhere in the amp... strange

I don't know what test gear you have... a scope and generator would help but I'll assume you haven't access to either.

You need to confirm that the six supplies to the faulty channels power amp are correct. Be very careful measuring, one slip will cause a lot of damage.

That's +50volts DC on Q902 and -50 volts DC on Q901.

And confirm the auxilliary supplies of +54 and +55 and - 54 and -55 volts DC from the regulator transistors Q801 and 802. Measure on the collector and emitter of each. These voltages will only be approximate and could be different by 10% or so... we are just confirming they are there.

Make sure these supplies arrive at the power amp as there are some safety resistors along the way.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 5th July 2011, 06:54 PM   #8
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
I don't have access to the gear you mentioned but I did check the transistors on the board. Q705's collector is showing 23.6v when it should read 0.8. My initial testing of the other transistors on that board shows numbers that are similar to the service manual's. Nothing as off the charts as Q705.

I will re-read your latest recommendations while I take a break.
  Reply With Quote
Old 5th July 2011, 07:00 PM   #9
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Just very quickly... and its not easy to read the circuit tbh... bit blurry

23 volts on Q705 collector ? Check the Base/Emitter volt drop across Q 708 (the driver) to the "top" output of the output pair. Is it open circuit ? Is the 5.6 ohm OK
Base/emitter going open circuit is a typical failure mode...

All the base emitter volt drops should not exceed around 0.8 volts max.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 5th July 2011, 07:19 PM   #10
diyAudio Member
 
Join Date: Jul 2011
Location: Oak Park, IL
Yeah, that upload is a bit blurry. Let's see if this one is better. My 11 month old son just woke up, so I'll do as you suggest once I get some free time later today .

Your help has given me greater confidence in finding the problem.
Attached Images
File Type: jpg schm02.jpg (108.2 KB, 125 views)
  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
Sony XM-2002GTR left channel bias Dr Zeus Car Audio 7 22nd June 2011 12:40 PM
Harmon Kardon 930 receiver weak left channel richmondscribe Solid State 8 24th April 2010 03:53 PM
Left channel not working with my speakers on my Technics SA-303 receiver ccevans6 Solid State 2 11th February 2010 05:11 PM
sony str-k840p issues freonchill Chip Amps 2 20th May 2008 01:02 PM
Sony STR-DE635 receiver no sound, what's blown? jamil5454 Solid State 42 16th September 2007 07:24 PM


New To Site? Need Help?

All times are GMT. The time now is 12:52 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