Can Transformer Hum Sound like a Crackling?

A

aussiblu

Guest
My Sanyo Combination Microwave EMC 8787B purchased from Target
frequently makes a low crackling just audible noise when it is
not in use but plugged in. The noise appears to be coming from
the front bottom right hand corner and sounds like something
arcing. The noise stops if the power is turned off at the wall.
The oven otherwise appears to work perfectly.

When I asked Sanyo via their customer support on their website
they said it was transformer hum, normal and safe. The sound is
coming from where they say the transformer is located but I
would expect transformer hum to be rhythmic with a fairly
constant frequency and volume - the crackling I hear randomly
changes in volume and frequency. What do you think. It's only
a few months old and still under warranty so I don't feel
disposed to opening up for further investigation.
--
Regards
Blue

Remove ZX from email address to reply directly.
 
On 12/12/2011 9:42 PM, aussiblu wrote:
My Sanyo Combination Microwave EMC 8787B purchased from Target
frequently makes a low crackling just audible noise when it is
not in use but plugged in. The noise appears to be coming from
the front bottom right hand corner and sounds like something
arcing. The noise stops if the power is turned off at the wall.
The oven otherwise appears to work perfectly.

When I asked Sanyo via their customer support on their website
they said it was transformer hum, normal and safe. The sound is
coming from where they say the transformer is located but I
would expect transformer hum to be rhythmic with a fairly
constant frequency and volume - the crackling I hear randomly
changes in volume and frequency. What do you think. It's only
a few months old and still under warranty so I don't feel
disposed to opening up for further investigation.
Click to expand...
You could try it on a different power circuit away from its current
location to see if it is an issue with power line noise.

Noises when not turned on would be enough inducement for me to take it
back regardless of what the Sanyo representative thinks it is.
Transformer hum is exactly that... a hum at 50 or 60 Hertz depending on
where you are. Crackling does not constitute a hum.

Take it back and say you think it is unsafe and are afraid it might
catch fire. Let them prove to you that it's safe. Don't just take their
word for it over the phone.

--

Krypsis
 
"aussiblu"

My Sanyo Combination Microwave EMC 8787B purchased from Target
frequently makes a low crackling just audible noise when it is
not in use but plugged in. The noise appears to be coming from
the front bottom right hand corner and sounds like something
arcing. The noise stops if the power is turned off at the wall.
The oven otherwise appears to work perfectly.

When I asked Sanyo via their customer support on their website
they said it was transformer hum, normal and safe. The sound is
coming from where they say the transformer is located but I
would expect transformer hum to be rhythmic with a fairly
constant frequency and volume - the crackling I hear randomly
changes in volume and frequency. What do you think. It's only
a few months old and still under warranty so I don't feel
disposed to opening up for further investigation.
Click to expand...
** See if the noise changes if the oven is bumped or tapped firmly with the
handle of a screwdriver in that area.

If it does react, then there is a bad connection or solder joint.

BTW the transformer in question is a tiny PCB one - right ?



.... Phil
 
"aussiblu" <zxaussiblu@bigpond.net.au> wrote in message
news:gUkFq.202$%E2.160@viwinnwfe01.internal.bigpond.com...
My Sanyo Combination Microwave EMC 8787B purchased from Target
frequently makes a low crackling just audible noise when it is
not in use but plugged in. The noise appears to be coming from
the front bottom right hand corner and sounds like something
arcing. The noise stops if the power is turned off at the wall.
The oven otherwise appears to work perfectly.

When I asked Sanyo via their customer support on their website
they said it was transformer hum, normal and safe. The sound is
coming from where they say the transformer is located but I
would expect transformer hum to be rhythmic with a fairly
constant frequency and volume - the crackling I hear randomly
changes in volume and frequency. What do you think. It's only
a few months old and still under warranty so I don't feel
disposed to opening up for further investigation.
Click to expand...

If it sounds like arcing you shouldn't have any difficulty convincing the
sales droid that there's no reason you should trust its safe.

If it has a front panel transformer for the display/micro it could be
anything from loose laminations to dry joints - I wouldn't accept that or
risk losing the warranty.
 
Thanks All


I'm in Bibra Lake Western Australia. Looking through the grill
for the oven light I can see a box shaped object about 40mm X
40m X 90mm which I assume is the transformer (there is also
evidence of matching mounting bolts on the bottom of the oven in
this area) . Unfortunately (or I guess for safety sakes,
fortunately) it and everything else there appears covered by
foil so without opening it up I can't confirm it's the
transformer or ID the type. Opening it will doubtless void my
warranty.

After comparing notes with the rest of the family, who more
frequently use this combination oven, I can add the following
observations:

a) It started crackling a few weeks ago with the onset of
hotter summer weather;
b) When it happens there is also a lot of condensation present
inside the oven (cooking area);
c) It stopped yesterday with a thunderstorm bringing cooler
temperatures - the condensation in the oven also disappeared at
the same time.

I can't help wondering if condensation is getting inside the
area where the transformer is and causing it or the mains
connections to short and arc. I assume this area should be
sealed off from the cooking compartment. I suspect this seal
has failed and moisture from cooking is getting into this area
or alternatively from outside the oven. Note my house is air
conditioned with ducted evaporative air conditioning - perhaps
that contributes to the formation of condensation. The oven is a
combination microwave, convection & grill.

..

--
Regards
Blue

Remove ZX from email address to reply directly.
 
I'm sure Target will give me my money back no questions asked
but I would prefer and exchange. However, I haven't found a
Target here in WA with them still in stock yet so given I
actually otherwise like this Combination Oven, and it was a
bargain price in comparison to others, I may have to accept
returning it to Sanyo for a warranty repair. I've emailed Sanyo
again.

--
Regards
Blue

Remove ZX from email address to reply directly.
 
On Dec 13, 9:02 pm, "aussiblu" <zxaussi...@bigpond.net.au> wrote:
I'm sure Target will give me my money back no questions asked
but I would prefer and exchange.  However, I haven't found a
Target here in WA with them still in stock yet so given I
actually otherwise like this Combination Oven, and it was a
bargain price in comparison to others, I may have to accept
returning it to Sanyo for a warranty repair. I've emailed Sanyo
again.

--
Regards
Blue

Remove ZX from email address to reply directly.
Click to expand...
as long as there arent any security seals on the case that break when
you open the case, it won't hurt to take a look.
 
It's a backlit LCD display.

Looking in through all the vent holes have discovered here and
there it looks like all that foil is everywhere and glued in
place which might present warranty problems if I open it up
(torn foil or one time adhesive strips). But having now found
all the various places I can look in when it starts crackling
again I will darken the room and peer in looking for evidence of
arcing

--
Regards
Blue

Remove ZX from email address to reply directly.
 
On Dec 13, 9:25 pm, kreed <kenreed1...@gmail.com> wrote:
On Dec 13, 9:02 pm, "aussiblu" <zxaussi...@bigpond.net.au> wrote:

I'm sure Target will give me my money back no questions asked
but I would prefer and exchange.  However, I haven't found a
Target here in WA with them still in stock yet so given I
actually otherwise like this Combination Oven, and it was a
bargain price in comparison to others, I may have to accept
returning it to Sanyo for a warranty repair. I've emailed Sanyo
again.

--
Regards
Blue

Remove ZX from email address to reply directly.

as long as there arent any security seals on the case that break when
you open the case, it won't hurt to take a look.
Click to expand...
Using a cardboard tube to listen through will help in locating the
sound, if you are unsure where it comes from. If it is dry joints
and you did get another oven, it would likely have dry joints also.


Just remembered something;

does it have one of those vacuum fluorescent displays ? I recall a
device years back with a large one of those displays and had a small
switching power supply using a pcb transformer run by a simple 2
transistor self excited oscillator [powered by the devices 12v rail]
to provide the special B+ voltage and filament voltages the display
needed.

One of them had a rather noisy transformer, that did at times actually
sound like it was crackling or arcing, it was coming from the small
SMPS transformer, but it was not dry joints (resoldered everything to
make sure) or any visible arcing. It was on 14 hours a day and did
this for 8 years or so that I know of, without any fault ever
happening.
 
On Dec 13, 10:25 pm, "aussiblu" <zxaussi...@bigpond.net.au> wrote:
It's a backlit LCD display.

Looking in through all the vent holes have discovered  here and
there it looks like all that foil is everywhere and glued in
place which might present warranty problems if I open it up
(torn foil or one time adhesive strips). But having now found
all the various  places I can look in when it starts crackling
again I will darken the room and peer in looking for evidence of
arcing

--
Regards
Blue

Remove ZX from email address to reply directly.
Click to expand...


If it has a switch mode supply for the electronics, even a basic one
like used in DVD players,
phone chargers etc, it might have a similar noise problem to what I
described ?


I would think that they would use a small PCB mount 50hz transformer
for this though,
but you never know these days with standby power standards and
similar ?.


Interestingly too, if a device is not actually doing its main intended
job (cooking in this case) but the display is
in time display (clock) mode does that consumption count as standby
power in any standard (if any) on this ?

.
 
The backlight only goes on if you press a button on its front
panel or you are cooking with it. Banging, knocking or moving
the oven made no difference.

The heat and humidity has returned post thunderstorms and the
condensation is starting to form inside the oven again; we'll se
if the arcing sound comes back.

Sanyo tried to ring me again today but we played unsuccessful
telephone tag.

--
Regards
Blue

Remove ZX from email address to reply directly.
 
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