Main transformer hum on Marantz amp
Grega Simenc
I've purchased a Marantz PM66 KI-S integrated amp about six months ago; I'm
extremely happy with it and I love it; but:
I have one problem with it. Sometimes the mains transformer (toroidal) gives
me a very loud hum or better, buzz. Even whole amps rattles slightly because
of this; it's very annoying and the buzz also comes out of left speaker when
it starts. But the big problem is that it's not permanent: it just happens
now or then (mostly once or twice per day for xx minutes and at yy.zz hour)
regardless which equipment in the house is turned on or off. I've tried
running it on different power outlets around the house and the problem
remains. It's not even related to amp's job: it starts if there's nothing
connected to the amp (disconnected speakers, interconnects) or if it's
playing from the two sources loud or quietly. I really don't know what to do
next: my Marantz service center is 60km away from my home and it would be
hard to explain such problem to the service personal.
Do any of you people have an advice that would share with me?
Thanks for reading.
Bye
Dave Platt
Grega Simenc <grga@*email4u.com*> wrote:
>I have one problem with it. Sometimes the mains transformer (toroidal) gives
>me a very loud hum or better, buzz. Even whole amps rattles slightly because
>of this; it's very annoying and the buzz also comes out of left speaker when
>it starts. But the big problem is that it's not permanent: it just happens
>now or then (mostly once or twice per day for xx minutes and at yy.zz hour)
>regardless which equipment in the house is turned on or off. I've tried
>running it on different power outlets around the house and the problem
>remains.
Mechanical humming and buzzing from a toroidal transformer usually
indicates that the powerline isn't delivering a clean 50- or 60-Hz
sinewave. Either there's a lot of harmonic distortion in the
powerline waveform, or it's asymmetrical (and thus has a DC
component). If it's bad enough to cause the whole amp to rattle, it's
pretty severe!
In many cases, this sort of problem can be traced to an appliance or
light fixture in the house which is drawing current from the powerline
in an asymmetrical fashion. Solid-state light dimmers are notorious
for causing this sort of problem.
Since you say that it doesn't depend on what equipment in the house is
in use, and affects all of your power circuits, I'd suggest looking
outside the house. In principle, equiment in any house or building
which is connected to the same power-distribution transformer could be
causing the problem - a heavy or asymmetrical current load from
manufacturing equipment (for example) or a welder could distort the
power at your outlets.
It could even be a problem affecting your whole neighborhood or city -
a defect in the power distribution system due to equipment overload or
failure somewhere in the "grid".
Unfortunately, there doesn't seem to be an easy or inexpensive
solution to this sort of problem. The suceptibility to humming and
buzzing is, to some extent, just one of the prices you pay for using a
toroid transformer. You can try replacing the transformer with one
which has been wound more tightly, or which has been
varnish-impregnated to hold the windings in place,or you can try
installing a big isolation transformer (a non-toroidal one!) between
your amp and the power outlet.
You might also see if any of your lights dim at the time that the
buzzing starts. If so, you may be able to persuade your power company
that the neighborhood distribution transformer is defective or too
small, and have them investigate the cause of the power problem.
--
Dave Platt dpl...@feghoot.ml.org
Visit the Jade Warrior home page: http://feghoot.ml.org/jade-warrior/
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David P. Greenberg
nuts that hold the toroid in place. 1 on the bottom of the amp, and one on
top of a steel plate that's mounted on top of the tranny. These can loosen
up over time and the steel plate will vibrate. It's like the pumps that are
used in fish tanks. These are usually just small transformers with a metal
tine clamped on top with a screw assembly' the tighter the screw the less
suction the pump can deliver. Take a couple of appropriately sized socket
wrenches, and tighten the thing down as tight as possible. This might just
do it.
--
David P. Greenberg
Bitco Electronics
"In Service to the Recording Industry"
www.tiac.net/users/bitco
Just chewing the virtual phat
Dave Platt wrote in message <73ncd6$ili$1...@supernews.com>...
Jerry G.
You say that you heard the buzz from out the speakers??? If you did
then you have a power supply problem. It is possible that you have
a filter cap and or a rectifier that is going bad...
As for mechanical vibration comming from a power transformer, this is
possible. Usualy tightning the mounting screws of the transformere
and or all the cabinet screws will help this.
Take care if you tighten screws related to the tyroid transformer.
There are some critical aspects to this, but they should not be loose.
Generaly there is one insulated screw sandwitching it with some large
type of some special washers. The transfomer should be seated so that
it will not rattle anything around it...
If the unit needs some troubleshooting, I would suggest you give it to
the experts if you are not a qaulified tech. I have seen too many
people screw up their equipment and then end up spending a lot more to
get it right...!
--
Jerry Greenberg
http://www.zoom-one.com/electron.htm
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============= Message Separator ================
Grega Simenc wrote in message <73n9ld$4uk$1...@planja.arnes.si>...
|Hi there,
|
|I've purchased a Marantz PM66 KI-S integrated amp about six months
ago; I'm
|extremely happy with it and I love it; but:
|
|I have one problem with it. Sometimes the mains transformer
(toroidal) gives
|me a very loud hum or better, buzz. Even whole amps rattles slightly
because
|of this; it's very annoying and the buzz also comes out of left
speaker when
|it starts. But the big problem is that it's not permanent: it just
happens
|now or then (mostly once or twice per day for xx minutes and at yy.zz
hour)
|regardless which equipment in the house is turned on or off. I've
tried
|running it on different power outlets around the house and the
problem
Mzacharias
You've confirmed the hum is from the transformer, right? Take it to a Marantz
authorized servicer under warranty and make them FIX IT.
Mark Z.
Marantz authorized servicer
Grega Simenc
Jerry wrote:
>You say that you heard the buzz from out the speakers??? If you did
>then you have a power supply problem. It is possible that you have
>a filter cap and or a rectifier that is going bad...
Well, not all the time - only when the transformer itself starts to buzz.
But it's only from the left speaker - this amp has a double mono circuit and
the left channel is very close to the transformer while right one is enough
away not to cause any other problems (at least that's my theory). Also, the
buzz from speakers is very light - I only hear it if I approach speaker and
listen to it from 10cm away or so. The transformer itself is much louder
when it starts...
>As for mechanical vibration comming from a power transformer, this is
>possible. Usualy tightning the mounting screws of the transformere
>and or all the cabinet screws will help this.
Well, I already opened the amp and unscrewed the transformer from the
cabinet. Guess what? It was buzzing and rattling while holding it 5cm away
from cabinet *in my hand*! The rattle of the transformer was light but when
the thing is screwed into case, vibrations spread all over the amp...
>Take care if you tighten screws related to the tyroid transformer.
>There are some critical aspects to this, but they should not be loose.
On the bottom, there is some soft material (more like a piece of gum) and
the transformer is sitting on this. It's screwed only with one going through
the middle of the transformer (that hole in the center of donut). On the top
is a piece of metal with a hole in the center for that screw(they say it's
completely out of copper - well, since when can copper get picked up with a
magnet?) which covers it (again, sort of gum between cover and the
transformer itself). It has two windings, one for powering output stage of
the amp and one for control circuits.
Also, I should point out that there are two other hi-fi sources connected to
the same power strip and they both don't give me any problems. But the
transformer in there are the normal ones...
I'll try to get hands on a 600VA UPS next week and to try with it - when the
transformer will start to rattle, I'll pull out the UPS from the power
socket (to simulate power faliure and to make UPS run on its batteries) -
that should give me the answer if the problem is with power network or the
transformer itself.
Anyway, thanks for replying and if anybody else knows anything else, please
let me know. Thanks very much.
Bye
Grega Simenc
>This is a good answer, but there's one thing I'd try first. There are two
>nuts that hold the toroid in place. 1 on the bottom of the amp, and one on
>top of a steel plate that's mounted on top of the tranny. These can loosen
Thanks very much for your reply, but check the other reply I wrote to the
Jerry.
Bye
Grega Simenc
first, thanks for your reply. Here's the mine:
Dave Platt wrote in message <73ncd6$ili$1...@supernews.com>...
>In many cases, this sort of problem can be traced to an appliance or
>light fixture in the house which is drawing current from the powerline
>in an asymmetrical fashion. Solid-state light dimmers are notorious
>for causing this sort of problem.
We have two solid-state dimmers in our house: I tried both and this is not
it...they don't have affect on the amp at all.
>which is connected to the same power-distribution transformer could be
>causing the problem - a heavy or asymmetrical current load from
>manufacturing equipment (for example) or a welder could distort the
>power at your outlets.
I live in a small town with about 2000 houses. There are several
distribution transformers and the one I'm connected to holds up about 200
houses. Yes, houses only: no big and power hungry companies around me. Also,
the electricity itself is pretty stable: maybe one dropout per year or so
and the light bulbs don't flicker at all.
>varnish-impregnated to hold the windings in place,or you can try
>installing a big isolation transformer (a non-toroidal one!) between
>your amp and the power outlet.
Hmm, I tried something like that: I had one big adjustable 'transformer' (it
was something else but I don't know english name for it) from 0V to 250V. I
tried connecting the amp through it but the buzzing was still there.
>You might also see if any of your lights dim at the time that the
>buzzing starts.
As I said, they're very stable. I've seen much worse electricity at friend's
houses, etc. I even tried unplugging refrigerators and such stuff around the
house but it doesn't help even a bit.
I really don't know what to do next: I will try connecting it through UPS
this week and see what happens.
If there's somebody with similar problems, please contact me. Thanks.
Bye
RODNEY BUIKE
the warranty thing, came back no fault found. The problem, my cheap
halogen floor lamp on dim setting. Off or on high, no buzzing, dim
setting, buzzes like crazy.
Rod
Visit my webpage at www.angelfire.com/mb/hifiguy/index.html for some
links to top home and car audio companies!!!!!!!
DUNCLIF
>The problem, my cheap
>halogen floor lamp on dim setting. Off or on high, no buzzing, dim
>setting, buzzes like crazy.
>
I have heard of this several other times and only with toroidal transformers.
It doesn't seem to happen as much with the other types. The trick with the UPS
might rule this out but only if the transformer doesn't hum because of the
output waveform from the UPS. Look for light dimmers and anything else that
might use a triac such as phase control for electric motors. Several companeys
sell these " power factor" controlers for the family fridg or freezer. The
little disks that can be put into light sockets to make bulbs last longer can
also do it. None of this will be covered by warranty.