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uk.rec.audio (General Audio and Hi-Fi) (uk.rec.audio) Discussion and exchange of hi-fi audio equipment.

'buzzing' amp - worth fixing?



 
 
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  #1 (permalink)  
Old March 12th 07, 01:12 PM posted to uk.rec.audio
AP
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Posts: 11
Default 'buzzing' amp - worth fixing?

Just got a Sherwood receiver (DAS RX-206ORDS) - quite nice, sounds
excellent - flawless - until it's been playing for around 45 mins, at which
point a buzzing begins inside the box. It's loud enough to be annoying.
Seems to be very localised - this is a ten year old beastie, all bits & bobs
rather than circuit boards - and my instinct is that it's one component in
there that's gone dodgy. Might it be worth repairing? Is it something I
could do, with a bit of common sense and a soldering iron? Or is it landfill
time? (I don't want to waste time & money on it, but it goes against the
grain to just junk something that's basically very good and, apart from this
one glitch, totally sound. Any help/advice appreciated.)


  #2 (permalink)  
Old March 12th 07, 08:54 PM posted to uk.rec.audio
Ian Bell
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Posts: 77
Default 'buzzing' amp - worth fixing?

AP wrote:

Just got a Sherwood receiver (DAS RX-206ORDS) - quite nice, sounds
excellent - flawless - until it's been playing for around 45 mins, at
which point a buzzing begins inside the box. It's loud enough to be
annoying. Seems to be very localised - this is a ten year old beastie, all
bits & bobs rather than circuit boards - and my instinct is that it's one
component in there that's gone dodgy. Might it be worth repairing? Is it
something I could do, with a bit of common sense and a soldering iron? Or
is it landfill time? (I don't want to waste time & money on it, but it
goes against the grain to just junk something that's basically very good
and, apart from this one glitch, totally sound. Any help/advice
appreciated.)


It sounds to me like as something heats up it starts to draw excessive
current which is causing the mains transformer to buzz with the extra load.
Can you locate the source of the buzz?

Ian
  #3 (permalink)  
Old March 12th 07, 10:03 PM posted to uk.rec.audio
AP
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Posts: 4
Default 'buzzing' amp - worth fixing?

Hi Ian

Thanks for responding. Yes, from a look thru' the grille I think it probably
is the transformer that's doing the actual buzzing. And I'm sure it is
heat - and in something fairly sizeable, such as a transformer, 'cos if you
turn it off and then turn it on a minute later, the buzzing is still there,
but if you leave it ten minutes then turn it back on, the buzzing's stopped.
Are transformers easy to change? Cheap? Easy to get hold of? Apologies for
the ignorance, but I am just that - ignorant. I should probably just bin it,
but like I say, it goes against the grain. Thanks again.

Alan
"Ian Bell" wrote in message
news:45f5d20f.0@entanet...
AP wrote:

Just got a Sherwood receiver (DAS RX-206ORDS) - quite nice, sounds
excellent - flawless - until it's been playing for around 45 mins, at
which point a buzzing begins inside the box. It's loud enough to be
annoying. Seems to be very localised - this is a ten year old beastie,

all
bits & bobs rather than circuit boards - and my instinct is that it's

one
component in there that's gone dodgy. Might it be worth repairing? Is it
something I could do, with a bit of common sense and a soldering iron?

Or
is it landfill time? (I don't want to waste time & money on it, but it
goes against the grain to just junk something that's basically very good
and, apart from this one glitch, totally sound. Any help/advice
appreciated.)


It sounds to me like as something heats up it starts to draw excessive
current which is causing the mains transformer to buzz with the extra

load.
Can you locate the source of the buzz?

Ian



  #4 (permalink)  
Old March 13th 07, 07:07 AM posted to uk.rec.audio
Phil Allison
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Posts: 927
Default 'buzzing' amp - worth fixing?


"AP"

Yes, from a look thru' the grille I think it probably
is the transformer that's doing the actual buzzing. And I'm sure it is
heat - and in something fairly sizeable, such as a transformer, 'cos if
you
turn it off and then turn it on a minute later, the buzzing is still
there,
but if you leave it ten minutes then turn it back on, the buzzing's
stopped.



** Ever figured out that transformers get hot ?

Are transformers easy to change? Cheap? Easy to get hold of?



** No to all the above.

Probably only needs bolts that hold the thing together tightened to fix the
buzz.



........ Phil




  #5 (permalink)  
Old March 13th 07, 09:45 AM posted to uk.rec.audio
AP
external usenet poster
 
Posts: 11
Default 'buzzing' amp - worth fixing?

Thanks Phil - I'll take the lid off tonite and look for bolts.

Alan
"Phil Allison" wrote in message
...

"AP"

Yes, from a look thru' the grille I think it probably
is the transformer that's doing the actual buzzing. And I'm sure it is
heat - and in something fairly sizeable, such as a transformer, 'cos if
you
turn it off and then turn it on a minute later, the buzzing is still
there,
but if you leave it ten minutes then turn it back on, the buzzing's
stopped.



** Ever figured out that transformers get hot ?

Are transformers easy to change? Cheap? Easy to get hold of?



** No to all the above.

Probably only needs bolts that hold the thing together tightened to fix
the buzz.



....... Phil






  #6 (permalink)  
Old March 13th 07, 09:53 AM posted to uk.rec.audio
Don Pearce
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Posts: 1,822
Default 'buzzing' amp - worth fixing?

On Tue, 13 Mar 2007 10:45:29 -0000, "AP"
wrote:

Thanks Phil - I'll take the lid off tonite and look for bolts.


Before you start tightening bolts, leave it on with the cover removed
until it is buzzing, then start gently pressing on bits (not delicate
bits of course) until you actually find what stops the buzzing when
you lean on it. Use a piece of wood or plastic so you don't get either
burnt or electrocuted, of course.

In all probability the buzz is associated with the transformer,
although it may not be the transformer itself that is buzzing, but
maybe something steel nearby that has come loose.

Many transformers don't have any means of tightening them - the core
laminations are clamped together by the bent metal cover. In that case
you may need to find yourself a small G-clamp to fit over the lams,
and just leave it there.

d

--
Pearce Consulting
http://www.pearce.uk.com
  #7 (permalink)  
Old March 13th 07, 11:22 AM posted to uk.rec.audio
AP
external usenet poster
 
Posts: 11
Default 'buzzing' amp - worth fixing?

Wonderful! Many thanks. Invaluable advice, much appreciated.

Alan
"Don Pearce" wrote in message
...
On Tue, 13 Mar 2007 10:45:29 -0000, "AP"
wrote:

Thanks Phil - I'll take the lid off tonite and look for bolts.


Before you start tightening bolts, leave it on with the cover removed
until it is buzzing, then start gently pressing on bits (not delicate
bits of course) until you actually find what stops the buzzing when
you lean on it. Use a piece of wood or plastic so you don't get either
burnt or electrocuted, of course.

In all probability the buzz is associated with the transformer,
although it may not be the transformer itself that is buzzing, but
maybe something steel nearby that has come loose.

Many transformers don't have any means of tightening them - the core
laminations are clamped together by the bent metal cover. In that case
you may need to find yourself a small G-clamp to fit over the lams,
and just leave it there.

d

--
Pearce Consulting
http://www.pearce.uk.com



  #9 (permalink)  
Old March 14th 07, 01:17 AM posted to uk.rec.audio
AP
external usenet poster
 
Posts: 4
Default 'buzzing' amp - worth fixing?

I have to say I really like the sound of that. Is it easy to remove &
replace said transformers? I have a feeling dunking it in situ might be
beyond me.
"Chris Isbell" wrote in message
...
On Tue, 13 Mar 2007 10:53:19 GMT, (Don Pearce)
wrote:

Many transformers don't have any means of tightening them - the core
laminations are clamped together by the bent metal cover. In that case
you may need to find yourself a small G-clamp to fit over the lams,
and just leave it there.


I have previously 'cured' buzzing transformers by dunking them in a
tin of varnish. Is this out of fashion these days?

Anyone trying this does so at their own risk!

--
Chris Isbell
Southampton, UK



  #10 (permalink)  
Old March 14th 07, 01:29 AM posted to uk.rec.audio
Phil Allison
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Posts: 927
Default 'buzzing' amp - worth fixing?


"AP"

** Do not TOP post.


I have previously 'cured' buzzing transformers by dunking them in a
tin of varnish. Is this out of fashion these days?

Anyone trying this does so at their own risk!


I have to say I really like the sound of that. Is it easy to remove &
replace said transformers? I have a feeling dunking it in situ might be
beyond me.



** Dunking is a last resort if the tranny has no bolts.

It will have to be oven baked for hours afterwards to dry the varnish - at
no more than 130 degrees C.



........ Phil


 




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