Clever telly and broken audio pre-amp
 

I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have
sensed that the audio pre-amp wasn't working. Maybe it looks for a
sensible load, I dunno. Clever though. And what to do about the pre-amp?

Bill

Clever telly and broken audio pre-amp
 

On Tue, 10 Dec 2013 21:45:01 +0000, Bill Wright wrote:

I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have
sensed that the audio pre-amp wasn't working. Maybe it looks for a
sensible load, I dunno. Clever though. And what to do about the pre-amp?

I'd start by checking the internal fuses on the power supply.
Of course, check the external one as well.
Then download the schematic from he
http://elektrotanya.com/rotel_rc-850.pdf/download.html

(mind you click on the obfuscated 'Get Manual' link and not anything else) and
then see where that leads you. PSU is dead simple and conventional and ought
to be easy to fix.

Clever telly and broken audio pre-amp
 

How was it connected to the set, merely by an analogue cable or was it one
of these hyper overkill machines with a fibre optic connection?

Brian

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Email:
__________________________________________________ __________________________________________________ __________


"Bill Wright" wrote in message
...
I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have sensed
that the audio pre-amp wasn't working. Maybe it looks for a sensible load,
I dunno. Clever though. And what to do about the pre-amp?

Bill

Clever telly and broken audio pre-amp
 

In article , Bill Wright
wrote:
So I'm thinking that the telly must have sensed that the audio pre-amp
wasn't working. Maybe it looks for a sensible load, I dunno. Clever
though.

I'm curious to know how it would do that. What type of connection between
them? I can imagine that something like HDMI might allow a handshake to
tell the TV. But don't know any general protocol for something like a pair
of phono/coax audio leads.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

Clever telly and broken audio pre-amp
 

"Brian Gaff" wrote in message ...

How was it connected to the set, merely by an analogue cable or was it one
of these hyper overkill machines with a fibre optic connection?
++++++++++++++++
I've got a fibre optic for those rare occasions when one of the HD channels
actually bothers to transmit full surround sound. Sadly these are all too
rare. but in any case, I doubt the TV could tell if it were a fibre cable
because they are, as far as I know, one way so the TV would continue beaming
at the amp, which would clearly do nothing.

I wonder if Bill's preamp has some sort of "relay" that switches the
electrical input in-circuit once the amp has powered up. A test might be
"does the TV do the same thing if you totally unplug the amp"? The TV would
then, as I think Bill said, detect no load to send audio too.

Paul DS.

Clever telly and broken audio pre-amp
 

"Bill Wright" wrote in message
...
I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have sensed
that the audio pre-amp wasn't working. Maybe it looks for a sensible load,
I dunno. Clever though. And what to do about the pre-amp?

Bill

Try power cycling it again.
And switching back and forth between internal and external sound.

Clever telly and broken audio pre-amp
 

Paul Ratcliffe wrote:
On Tue, 10 Dec 2013 21:45:01 +0000, Bill Wright wrote:

I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have
sensed that the audio pre-amp wasn't working. Maybe it looks for a
sensible load, I dunno. Clever though. And what to do about the pre-amp?

I'd start by checking the internal fuses on the power supply.
Of course, check the external one as well.
Then download the schematic from he
http://elektrotanya.com/rotel_rc-850.pdf/download.html

(mind you click on the obfuscated 'Get Manual' link and not anything else) and
then see where that leads you. PSU is dead simple and conventional and ought
to be easy to fix.

Cheers.

Bill

Clever telly and broken audio pre-amp
 

Brian Gaff wrote:
How was it connected to the set, merely by an analogue cable or was it one
of these hyper overkill machines with a fibre optic connection?

Brian


Just ordinary wire...

Bill

Clever telly and broken audio pre-amp
 

R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
I switched on my lovely big Sony telly and a strange message appeared.
'Searching for external loudspeakers'. Never seen that before. When the
telly came on there was no sound. It's set up for its own speakers to be
muted. It turned out that the audio pre-amp (a Rotel RC850) had failed.
We've recently had two power cuts, plus the RCD firing due to a faulty
kettle. For the time being I've bypassed the preamp, taking the TV audio
straight to the power amp. So I'm thinking that the telly must have sensed
that the audio pre-amp wasn't working. Maybe it looks for a sensible load,
I dunno. Clever though. And what to do about the pre-amp?

Bill

Try power cycling it again.
And switching back and forth between internal and external sound.


The pre-amp is the same on all inputs. I have four things feeding into
it and they're all the same: very weak audio at the pre-amp output.

Bill

Clever telly and broken audio pre-amp
 

On 2013-12-11, Bill Wright wrote:
Brian Gaff wrote:
How was it connected to the set, merely by an analogue cable or was it one
of these hyper overkill machines with a fibre optic connection?

Brian


Just ordinary wire...

Well there's your problem.

You clearly need directional, oxygen-free, gold-plated interconnects
hand-crafted by a Tibbetan Yak.

--
David Taylor