Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
motsco_ _
 
Posts: n/a
Default __ Two Sony recievers that have buzzing STR-AV920, STR-D990

They're both mine, and they buzz thru the speakers even though volume is
all the way down. It sounds like it's getting louder by the day, and may
be 120HZ. I'm capable of changing capacitors, though none look like
they've been hot. Machines are both around 15 years old. Should i start
with the two big honking capacitors on the P.S. ?

motsco_ _
--

To REPLY: If there are a couple of underscores in my return address,
you must remove them to reply directly . . . . . . Thanks.

  #2   Report Post  
Mark D. Zacharias
 
Posts: n/a
Default

These have a known problem with the screws which make the ground connections
at the various corners and edges of the main board, the power supply board,
and the heat sink.

Tighten them.


Mark Z.


"motsco_ _" "motsco_ wrote in message
...
They're both mine, and they buzz thru the speakers even though volume is
all the way down. It sounds like it's getting louder by the day, and may
be 120HZ. I'm capable of changing capacitors, though none look like
they've been hot. Machines are both around 15 years old. Should i start
with the two big honking capacitors on the P.S. ?

motsco_ _
--

To REPLY: If there are a couple of underscores in my return address, you
must remove them to reply directly . . . . . . Thanks.



  #3   Report Post  
Dave VanHorn
 
Posts: n/a
Default

Bad caps don't necessarily look bad. They slowly reduce in effective value,
due to age. You may see a 1000uF that measures to significantly less than
that, like 100uF.



  #4   Report Post  
James Sweet
 
Posts: n/a
Default


"Dave VanHorn" wrote in message
...
Bad caps don't necessarily look bad. They slowly reduce in effective

value,
due to age. You may see a 1000uF that measures to significantly less than
that, like 100uF.




More often than that, they'll measure ok, but the ESR has gone way up and
acts like a resistor in series with them.


  #5   Report Post  
Jerry G.
 
Posts: n/a
Default

The main filter capacitors, and most likely a number of decoupler caps in
the power supply are probably going defective. If you are not used to doing
this type of service, I suggest you give the units out to a shop that can
service your amplifier. Take care that there are also safety issues involved
when doing repairs yourself.

--

Jerry G.
======


"motsco_ _" "motsco_ wrote in message
...
They're both mine, and they buzz thru the speakers even though volume is
all the way down. It sounds like it's getting louder by the day, and may
be 120HZ. I'm capable of changing capacitors, though none look like
they've been hot. Machines are both around 15 years old. Should i start
with the two big honking capacitors on the P.S. ?

motsco_ _
--

To REPLY: If there are a couple of underscores in my return address,
you must remove them to reply directly . . . . . . Thanks.




  #6   Report Post  
Mark D. Zacharias
 
Posts: n/a
Default

I repeat. Known problem. Tighten the screws. Resoldering some driver
transistors etc might also be a good idea considering the age of the unit.

Mark Z.


"Jerry G." wrote in message
...
The main filter capacitors, and most likely a number of decoupler caps in
the power supply are probably going defective. If you are not used to
doing
this type of service, I suggest you give the units out to a shop that can
service your amplifier. Take care that there are also safety issues
involved
when doing repairs yourself.

--

Jerry G.
======


"motsco_ _" "motsco_ wrote in message
...
They're both mine, and they buzz thru the speakers even though volume is
all the way down. It sounds like it's getting louder by the day, and may
be 120HZ. I'm capable of changing capacitors, though none look like
they've been hot. Machines are both around 15 years old. Should i start
with the two big honking capacitors on the P.S. ?

motsco_ _
--

To REPLY: If there are a couple of underscores in my return address,
you must remove them to reply directly . . . . . . Thanks.




  #7   Report Post  
motsco_ _
 
Posts: n/a
Default

James Sweet wrote:
"Dave VanHorn" wrote in message
...

Bad caps don't necessarily look bad. They slowly reduce in effective


value,

due to age. You may see a 1000uF that measures to significantly less than
that, like 100uF.


More often than that, they'll measure ok, but the ESR has gone way up and
acts like a resistor in series with them.


-------------------

Thanks, all for replying. The caps are coming in a week, and it sounds
like a great place to start. I noticed they did smell a bit funny when
removed. We'll see. I'll report back.

'Curly'

Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
I dropped the tv ( Sony circa December 1985) Accidents HAPPEN Electronics Repair 18 June 22nd 04 05:54 AM
1991 Sony 8MM Camcorder real wierd problem --need expert help Ron G Electronics Repair 1 January 26th 04 09:11 PM
Sony G500 Monitor Repair Bob Electronics Repair 1 July 24th 03 04:52 AM
Sony G500 Monitor Repair bigmike Electronics Repair 0 July 23rd 03 09:01 AM
Sony G410R Monitor problem (and bad Sony support) Steeve M Electronics Repair 7 July 15th 03 12:24 AM


All times are GMT +1. The time now is 09:42 AM.

Powered by vBulletin® Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright 2004-2023 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"