Faulty amplifier
 

I've just been given a mini-system - Denon D-110. The type that's
connected with ribbons. Anyway, it all lights up and appears to operate,
but no sound. Low level of hiss increases when the volume control turned
up, very slight signal on phono, but nothing through aux or the other
components.

Opened it up and checked all the fuses - fine. However, this:

http://www.flickr.com/photos/4771747...57634354546719

The heatsink securing screws are loose, fingerprints in the messy
thermal paste. I take it this is a bodged repair, and the likely source
of the problem?

Thanks, Rob

Faulty amplifier
 

In article , RJH
wrote:
I've just been given a mini-system - Denon D-110. The type that's
connected with ribbons. Anyway, it all lights up and appears to operate,
but no sound. Low level of hiss increases when the volume control
turned up, very slight signal on phono, but nothing through aux or the
other components.

Opened it up and checked all the fuses - fine. However, this:

http://www.flickr.com/photos/4771747...57634354546719

The heatsink securing screws are loose, fingerprints in the messy
thermal paste. I take it this is a bodged repair, and the likely source
of the problem?

I can't really tell just from the photo. It looks like the 'amp' is
essentially a module which fits onto the circuit board. Or maybe a block of
output devices, etc, driven by a previous gain stage not visible. Whoever
it was presumably tried a repair because it went wrong for some other
reason than the module not being fitted as shown.

Not clear if it is the original that has been removed and poorly refitted,
or a replacement. I can't tell from here be it gave me the impression
someone soldered in the module, then found it wouldn't mate well enough to
do up the heatsink screws! If so, classic example of how A and B don't
commutate. :-)

Having a lead not connected because the screw isn't done up may not help
much.

What do the usual bits of kit - scope, meter, etc - tell you? And have you
done a search for the part number?

Slainte,

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
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Faulty amplifier
 

On 27/06/2013 16:18, Jim Lesurf wrote:
In article , RJH
wrote:
I've just been given a mini-system - Denon D-110. The type that's
connected with ribbons. Anyway, it all lights up and appears to operate,
but no sound. Low level of hiss increases when the volume control
turned up, very slight signal on phono, but nothing through aux or the
other components.

Opened it up and checked all the fuses - fine. However, this:

http://www.flickr.com/photos/4771747...57634354546719

The heatsink securing screws are loose, fingerprints in the messy
thermal paste. I take it this is a bodged repair, and the likely source
of the problem?

I can't really tell just from the photo. It looks like the 'amp' is
essentially a module which fits onto the circuit board. Or maybe a block of
output devices, etc, driven by a previous gain stage not visible. Whoever
it was presumably tried a repair because it went wrong for some other
reason than the module not being fitted as shown.


I really can't tell. The pins appear to be neatly soldered to the board.
I think the STK4171V is a power amp module:

http://www.repairfaq.org/sam/chippins.htm#cpSTK4171V


Not clear if it is the original that has been removed and poorly refitted,
or a replacement. I can't tell from here be it gave me the impression
someone soldered in the module, then found it wouldn't mate well enough to
do up the heatsink screws! If so, classic example of how A and B don't
commutate. :-)


It is odd. The screws were both cross-threaded and just catching. I'd
imagine the module would simply overheat?

I've now screwed them in correctly - the heatsink just needed re-seating
slightly. The amp has been on an hour and the module is stone cold.

Having a lead not connected because the screw isn't done up may not help
much.


Still doesn't work!

What do the usual bits of kit - scope, meter, etc - tell you? And have you
done a search for the part number?


I only have a basic voltmeter, and a basic brain with which to operate
it. I'd try swapping out the module if it wasn't too expensive - but any
more than that would be well beyond me. Any basic diagnostic tips
appreciated.

Thanks, Rob

Faulty amplifier
 

In article ,
RJH wrote:
I've just been given a mini-system - Denon D-110. The type that's
connected with ribbons. Anyway, it all lights up and appears to operate,
but no sound. Low level of hiss increases when the volume control
turned up, very slight signal on phono, but nothing through aux or the
other components.

Opened it up and checked all the fuses - fine. However, this:

http://www.flickr.com/photos/4771747...57634354546719

The heatsink securing screws are loose, fingerprints in the messy
thermal paste. I take it this is a bodged repair, and the likely source
of the problem?

I *think* that is purely the power amp, so if the hiss increases with the
volume control it may be ok. You should be able to download a schematic
for it easily enough. And maybe even the whole thing.

--
*How come you never hear about gruntled employees? *

Dave Plowman London SW
To e-mail, change noise into sound.

Faulty amplifier
 

I only have a basic voltmeter, and a basic brain with which to operate
it. I'd try swapping out the module if it wasn't too expensive - but any
more than that would be well beyond me. Any basic diagnostic tips
appreciated.

Thanks, Rob



You really need a circuit diagram even if you have a fair bit of
experience your still working rather blind.

To recap.

You say you have no audio thru it on either channel and its stone cold?.
I'd expect it to be very slightly warm. You say as you turn up the
volume control you hear a slight hiss?. If that is the case then it
seems to power amp stages are working.

That being so turn up the volume and gently prod each terminal on the
amp chip and the volume control with your finger gently the idea is to
inject a bit of mains "hum" into the amp its a rudimentary test signal.

MAKE CERTAIN you don't touch the mains supply at all!!.

When testing anything like this keep one hand in your pocket it's to
guard against getting any electrical shock across the most vulnerable
part of your body the heart and chest area!..


Further I'd check that that chip is firmly screwed to the heat sink
before much longer;!..

All the above given in good faith but you do any of that at your own
risk of course..
--
Tony Sayer

Faulty amplifier
 

"RJH"


I've now screwed them in correctly - the heatsink just needed re-seating
slightly. The amp has been on an hour and the module is stone cold.


** Not too unusual.


I only have a basic voltmeter, and a basic brain with which to operate it.
I'd try swapping out the module if it wasn't too expensive - but any more
than that would be well beyond me. Any basic diagnostic tips appreciated.

**Look at the back and see if there are any RCA sockets that allow the
connection an external device between the pre amp and power amp - often
labelled "pre out" and "amp in".

If so - run a pair of RCA leads between them.

Many such amps have U shaped links fitted when new and owners toss them.



.... Phil

Faulty amplifier
 

On 28/06/2013 04:51, Phil Allison wrote:
"RJH"


I've now screwed them in correctly - the heatsink just needed re-seating
slightly. The amp has been on an hour and the module is stone cold.


** Not too unusual.


Indeed!


I only have a basic voltmeter, and a basic brain with which to operate it.
I'd try swapping out the module if it wasn't too expensive - but any more
than that would be well beyond me. Any basic diagnostic tips appreciated.

**Look at the back and see if there are any RCA sockets that allow the
connection an external device between the pre amp and power amp - often
labelled "pre out" and "amp in".

If so - run a pair of RCA leads between them.

Many such amps have U shaped links fitted when new and owners toss them.


Yep - you're quite right! It has a 'Processor Loop'. I've since
downloaded a German copy of the manual - the diagram shows what look
like bus bars connecting the 'in' and 'out'. Nowhere to be seen. RCA
leads connected and it's sprung to life.

Thanks very much.

Incidentally, one of the speakers (the reason I was there, and given the
system) had a non-working tweeter. The fault was on the crossover. A
wire linking a capacitor and resistor was simply twisted and, while
still touching, no longer conducted the signal. Speakers made for Denon
by JPW I think.

Rob

Faulty amplifier
 

On 27/06/2013 21:31, tony sayer wrote:
I only have a basic voltmeter, and a basic brain with which to operate
it. I'd try swapping out the module if it wasn't too expensive - but any
more than that would be well beyond me. Any basic diagnostic tips
appreciated.

Thanks, Rob



You really need a circuit diagram even if you have a fair bit of
experience your still working rather blind.

To recap.

You say you have no audio thru it on either channel and its stone cold?.
I'd expect it to be very slightly warm. You say as you turn up the
volume control you hear a slight hiss?. If that is the case then it
seems to power amp stages are working.

That being so turn up the volume and gently prod each terminal on the
amp chip and the volume control with your finger gently the idea is to
inject a bit of mains "hum" into the amp its a rudimentary test signal.

MAKE CERTAIN you don't touch the mains supply at all!!.

When testing anything like this keep one hand in your pocket it's to
guard against getting any electrical shock across the most vulnerable
part of your body the heart and chest area!..


Further I'd check that that chip is firmly screwed to the heat sink
before much longer;!..

All the above given in good faith but you do any of that at your own
risk of course..


Thanks for that - good tips. As replied elsewhere - the fault was with
the user :-)

Rob

Faulty amplifier
 

"RJH"
Phil Allison wrote:
"RJH"


I've now screwed them in correctly - the heatsink just needed re-seating
slightly. The amp has been on an hour and the module is stone cold.


** Not too unusual.

Indeed!

I only have a basic voltmeter, and a basic brain with which to operate
it.
I'd try swapping out the module if it wasn't too expensive - but any
more
than that would be well beyond me. Any basic diagnostic tips
appreciated.

**Look at the back and see if there are any RCA sockets that allow the
connection an external device between the pre amp and power amp - often
labelled "pre out" and "amp in".

If so - run a pair of RCA leads between them.

Many such amps have U shaped links fitted when new and owners toss them.


Yep - you're quite right! It has a 'Processor Loop'. I've since downloaded
a German copy of the manual - the diagram shows what look like bus bars
connecting the 'in' and 'out'. Nowhere to be seen. RCA leads connected and
it's sprung to life.

Thanks very much.


** Ah - another satisfied customer !!!!!

Visiting a taxidermist is not necessary.



.... Phil