NAD 3125 amp whooshing noise while powering on.

[David Farber]

I have an NAD 3125 power amp. Approximately 15 seconds after it is powered
on, there is a whooshing noise and then the audio comes on and plays
normally. There is no conventional speaker relay that clicks (at least I
can't find one). I imagine there is some sort of power up muting circuit but
the whooshing sound doesn't seem normal. I cannot find a schematic for this
model and was wondering if this symptom sounded familiar to anyone.

Thanks for your reply.
--
David Farber
Los Osos, CA

 

[Phil Allison]

"David Farber"

I have an NAD 3125 power amp.

** Fraid that is an integrated amp.

Approximately 15 seconds after it is powered on, there is a whooshing
noise and then the audio comes on and plays normally. There is no
conventional speaker relay that clicks (at least I can't find one). I
imagine there is some sort of power up muting circuit but the whooshing
sound doesn't seem normal. I cannot find a schematic for this model and
was wondering if this symptom sounded familiar to anyone.

** Not very unusual - one likely cause is poor contacts on control pots and
switches.

As the coupling caps in the amp charge after switch on, brief DC voltages
are applied to many pots and switches - if the contact is corroded ( ie
tarnished) some noise will be generated.

Some cleaning fluid should be applied to all the parts where this can happen
and the control or switch operated vigorously for a few seconds afterwards.

IME the kinds of fluid that evaporate quickly are useless and the oil and
solvent based one like WD40 are by far the best for this.


.... Phil

 

[Mark Zacharias]

"David Farber" <farberbear.unspam@aol.com> wrote in message
news:j9jukv$68a$1@dont-email.me...

I have an NAD 3125 power amp. Approximately 15 seconds after it is powered
on, there is a whooshing noise and then the audio comes on and plays
normally. There is no conventional speaker relay that clicks (at least I
can't find one). I imagine there is some sort of power up muting circuit
but the whooshing sound doesn't seem normal. I cannot find a schematic for
this model and was wondering if this symptom sounded familiar to anyone.

Thanks for your reply.
--
David Farber
Los Osos, CA

I have seen this before. It is the audio "un-muting" circuit I'm pretty
sure.

I can probably scan the schematic and send it to you, I'm pretty sure I have
a hard copy somewhere.

email me direct and I'll reply with the schem.

mark_zacharias@labolgcbs.net and reverse "labolgcbs" to read "sbcglobal" .

mz

 

[David Farber]

Mark Zacharias wrote:

"David Farber" <farberbear.unspam@aol.com> wrote in message
news:j9jukv$68a$1@dont-email.me...
I have an NAD 3125 power amp. Approximately 15 seconds after it is
powered on, there is a whooshing noise and then the audio comes on
and plays normally. There is no conventional speaker relay that
clicks (at least I can't find one). I imagine there is some sort of
power up muting circuit but the whooshing sound doesn't seem normal.
I cannot find a schematic for this model and was wondering if this
symptom sounded familiar to anyone. Thanks for your reply.
--
David Farber
Los Osos, CA


I have seen this before. It is the audio "un-muting" circuit I'm
pretty sure.

I can probably scan the schematic and send it to you, I'm pretty sure
I have a hard copy somewhere.

email me direct and I'll reply with the schem.

mark_zacharias@labolgcbs.net and reverse "labolgcbs" to read
"sbcglobal" .
mz

I really didn't find any bad transistors or caps. So I removed the left and
right channel muting transistors and the whooshing noise disappeared. Not
sure why the transistors needed to be there in the first place. When powered
up now, there is just has a very slight thumping noise through the speakers
which was present before the transistors were removed. In case you're
wondering, the transistors are Q102 and Q202.
--

David Farber
Los Osos, CA

 

On Friday, November 11, 2011 1:53:43 PM UTC-6, David Farber wrote:

I have an NAD 3125 power amp. Approximately 15 seconds after it is powered

on, there is a whooshing noise and then the audio comes on and plays

normally. There is no conventional speaker relay that clicks (at least I

can't find one). I imagine there is some sort of power up muting circuit but

the whooshing sound doesn't seem normal. I cannot find a schematic for this

model and was wondering if this symptom sounded familiar to anyone.



Thanks for your reply.

--

David Farber

Los Osos, CA

David - I have the same issue with my NAD 3125. I have the schematic but am a bit of a novice. Any advice or clue as to locate the Q102 & Q202 muting transisters?

 

[Gareth Magennis]

wrote in message
news:f3b171b8-39fa-44f0-91f2-1bf6634b8af4@googlegroups.com...

On Friday, November 11, 2011 1:53:43 PM UTC-6, David Farber wrote:

I have an NAD 3125 power amp. Approximately 15 seconds after it is powered

on, there is a whooshing noise and then the audio comes on and plays

normally. There is no conventional speaker relay that clicks (at least I

can't find one). I imagine there is some sort of power up muting circuit
but

the whooshing sound doesn't seem normal. I cannot find a schematic for
this

model and was wondering if this symptom sounded familiar to anyone.



Thanks for your reply.

--

David Farber

Los Osos, CA

David - I have the same issue with my NAD 3125. I have the schematic but am
a bit of a novice. Any advice or clue as to locate the Q102 & Q202 muting
transisters?






They are likely to be Mosfets, 2SJ XXX or 2SK XXX?

I don't usually repair hi-fi, but the most common ones on pro audio
equipment are J111 - J113.

I find it is very easy to spot the abbreviated "J11x" marking, being very
different to the usual transistor ID marks.




Cheers,


Gareth.