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OT Repair of Sony AV S800 Home Theater System
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Davidm
Oct 26, 2017, 7:26:57 AM10/26/17
to
I've got a Sony DAV S800 Home Theater System that has a problem and
needs repairing. It's a CD/DVD player, FM tuner and 5 channel surround
sound amp, and the front left speaker output has a temperature (I
think) related problem, in that it doesn't start working until the
unit has been switched on for 10 minutes or so, after which it's fine.
I've tried swopping speaker connections on the back of the unit, no
difference, so the problem is in the unit itself, not the speaker or
cables. I've had the lid off and visually checked the connections of
the speaker socket to the circuit board, no obvious sign of breakage
or dry joint, and I don't have the test equipment to take things
further, although I do have the circuit diagrams for it.
Anyone know of somewhere mid Hertfordshire (Watford, St Albans etc.)
area that might be able to repair it?
It serves it's purpose, so I'm reluctant to bin it!
needs repairing. It's a CD/DVD player, FM tuner and 5 channel surround
sound amp, and the front left speaker output has a temperature (I
think) related problem, in that it doesn't start working until the
unit has been switched on for 10 minutes or so, after which it's fine.
I've tried swopping speaker connections on the back of the unit, no
difference, so the problem is in the unit itself, not the speaker or
cables. I've had the lid off and visually checked the connections of
the speaker socket to the circuit board, no obvious sign of breakage
or dry joint, and I don't have the test equipment to take things
further, although I do have the circuit diagrams for it.
Anyone know of somewhere mid Hertfordshire (Watford, St Albans etc.)
area that might be able to repair it?
It serves it's purpose, so I'm reluctant to bin it!
Woody
Oct 26, 2017, 12:05:47 PM10/26/17
to
"Davidm" <davidm_...@hotmail.com> wrote in message
news:5sg3vcp1s75b3vpj8...@4ax.com...
starts playing did you hear a mechanical click from the unit just as
the sound started?
Modern amps use +ve and -ve supply rails so the loudspeaker output
sits at 0V (in terms of d.c.) and the series capacitor (that causes a
thump at switch-on) can be removed. Often they have a relay in series
with the speaker to allow time for the sensing circuits to decide if
there is a d.c. offset on the output to protect the speaker.
If there is a click just as the speaker comes to life it suggests that
there is a d.c. biasing issue in the amp which reduces to acceptable
levels as the output stages warm up. Simple check: disconnect the
speakers and switch the amp on from cold with a DVM connected across
the right speaker terminals. There should be no more than about 100mV
d.c. present possibly after maybe 10 seconds. Now repeat from a cold
start whilst measuring the left speaker. If my theory is correct then
you will see 0V across the speaker terminals until the 10 minutes has
passed (and you may hear a click) and a small voltage suddenly appears
across the connection.
It should not be a major problem for a competent engineer to fix -
except you have to find one! Richers used to have a service dept - you
can but ask?
--
Woody
harrogate3 at ntlworld dot com
Brian Gaff
Oct 26, 2017, 1:00:33 PM10/26/17
to
Well is there any hiss or buzz on the dodgy channel when it in fault mode?
If there is its an early stage fault if not it might be in the output part,
I think that is as far as I can go. I assume the output section on each
channel is the same for all, and its probably analogue by then, so one might
be able to find it by f just making it buzz with a probe on a good channel
and gradually work back to see where it stops on the duff one since you have
the circuit. Trouble is many of these things vanish into a surface mount
chip all too soon and hence it complicates this way of working these days.
One small idea. If it has a speaker relay for all channels maybe its just
got one dirty contact thet eventually makes contact. I have a denon like
that but in that case you tend to get distortion due to the contact not
making very well and it can go of or on at random, so if this is heat
related its probably some chip or semiconductor either with a problem
internally or in the soldering.
Brian
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If there is its an early stage fault if not it might be in the output part,
I think that is as far as I can go. I assume the output section on each
channel is the same for all, and its probably analogue by then, so one might
be able to find it by f just making it buzz with a probe on a good channel
and gradually work back to see where it stops on the duff one since you have
the circuit. Trouble is many of these things vanish into a surface mount
chip all too soon and hence it complicates this way of working these days.
One small idea. If it has a speaker relay for all channels maybe its just
got one dirty contact thet eventually makes contact. I have a denon like
that but in that case you tend to get distortion due to the contact not
making very well and it can go of or on at random, so if this is heat
related its probably some chip or semiconductor either with a problem
internally or in the soldering.
Brian
--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please!
Brian Gaff
Oct 26, 2017, 1:15:17 PM10/26/17
to
I remember some years ago, I had a rather nice Din based receiver made by
Tandy, and branded memorex. It was great until one day its right hand
channel melted the speaker voice coil and then bew the fuse. Obviously the
protection was non existent when a component failed.
Looking inside it had bits branded Tandberg, so I suspect his particular
device was knocked out for all sorts of brands back in the 70s. Just cos it
was old did not make it nice though.
Old memories.
news:ost4bg$40a$1...@news.albasani.net...
Tandy, and branded memorex. It was great until one day its right hand
channel melted the speaker voice coil and then bew the fuse. Obviously the
protection was non existent when a component failed.
Looking inside it had bits branded Tandberg, so I suspect his particular
device was knocked out for all sorts of brands back in the 70s. Just cos it
was old did not make it nice though.
Old memories.
Brian
--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please!
"Brian Gaff" <bri...@blueyonder.co.uk> wrote in message
--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
bri...@blueyonder.co.uk
Blind user, so no pictures please!
news:ost4bg$40a$1...@news.albasani.net...
Phi
Oct 26, 2017, 2:51:19 PM10/26/17
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"Woody" <harro...@ntlworld.com> wrote in message
news:ost14e$8g7$1...@dont-email.me...
comes on and selectively spray likely components until the speaker goes off.
This should identify the area with the problem.
Davidm
Oct 28, 2017, 5:06:16 AM10/28/17
to
On Thu, 26 Oct 2017 17:06:10 +0100, "Woody" <harro...@ntlworld.com>
wrote:
Thanks Woody. The circuit diagrams do show relays in the speaker
circuit. Unfortunately I only have a simple handheld multimeter, not
sure if it will register 100mV, I'll have to check.
Richer do have a repair service, but they want Ł65 to even look at the
amp.
wrote:
circuit. Unfortunately I only have a simple handheld multimeter, not
sure if it will register 100mV, I'll have to check.
Richer do have a repair service, but they want Ł65 to even look at the
amp.
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