__ Two Sony recievers that have buzzing STR-AV920, STR-D990

[motsco_ _]

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_ _

 

[Mark D. Zacharias]

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.

 

[Dave VanHorn]

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.

 

[James Sweet]

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.

 

[Jerry G.]

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.
======


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_ _

 

[Mark D. Zacharias]

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.

 

[motsco_ _]

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'