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Dangerous PC Speakers

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Phil Allison

Jan 1, 1970
0
Hi to all,

When I upgraded my PC recently a pair of small, self powered speakers
were included in the deal.

These were the Lepra brand model LS699.

After a while I noticed a burning smell coming from the area of the
monitor but it was not that - the speaker with the PSU and amp inside was
the culprit. On opening it I found the tiny PC mount transformer (no plug
pack is used) was running so hot it had blackened the insulation tape on the
primary winding and was much too hot to touch.

The tranny would be about 2 or 2.5 VA from its size ( core 28 x 25 x
12mm ) and powered a TDA2822M 8 pin dual amp IC - but only just. The
primary magnetising current measured 37mA and the resistance about 3500 ohms
when hot - that means almost 5 watts of heat loss in the primary alone - no
wonder it was so damn hot !!

The tranny has only *basic insulation* and no thermal fuse - the
plastic bobbin melts like butter if you apply a soldering iron. There is
only 0.7mm of plastic separating the windings.

There is strangely no double insulation symbol on the unit, but there
is an approval number ( N 10752) - for all that is worth.

I am concerned that some trannies will burn and fail with a breakdown
from primary to secondary and make the input plug live.


Any one else seen this problem or another similar one ??



.............. Phil
 
J

JM

Jan 1, 1970
0
That approval number is only in relation to its c-tick compliance, it may
burn your house down, but there won't be any interference on your tv in the
process.

JM
 
P

Phil Allison

Jan 1, 1970
0
David said:
someone actually dies then it is highly unlikley the NSW DFT would
take any action over a non-declared article.



** Hitting a nail on the head is not in the same league as driving
nails into someone's coffin.



............ Phil
 
A

Andy, The Real

Jan 1, 1970
0
Phil Allison said:
** Hitting a nail on the head is not in the same league as driving
nails into someone's coffin.

People die and they still dont give a shit. Ask QLD's GRAVES (or whtever
they are called) and they will tell you how to fix the problem. Then
everyone will complain because they cant get their product certified, just
like the QLD electrical laws.....blah blah blah..
 
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