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From: powerampfreak on 13 Jun 2010 17:16
I was given an oscilloscope, a Fluke PM3082 from a retired industrial
electronics engineer.
He said that during a measurement, the oscilloscope's powersupply just
bang and a flame came out of the rear panel. After this, the scope was
left for several years...until I got it.
The mains fuse has really exploded. Shattered glass in the fuse
holder. A brief examination of the primary side of the smps reveals no
shorts. The smps is an ordinary flyback supply. Mains rectifier ok,
switch ok, snubber, line filters all ok. Really don't know why the
mains fuse went.
I just don't want to put a new fuse in and try again, not before I
investigate the cause.
Could an incorrect measurement setup cause the mains fuse to explode?
Anyone familiar with these scopes or perhaps has a service manual for
it?
Best regards
PAF
From: Meat Plow on 13 Jun 2010 18:04
On Sun, 13 Jun 2010 14:16:36 -0700, powerampfreak ǝʇoɹʍ:

> I was given an oscilloscope, a Fluke PM3082 from a retired industrial
> electronics engineer.
> He said that during a measurement, the oscilloscope's powersupply just
> bang and a flame came out of the rear panel. After this, the scope was
> left for several years...until I got it. The mains fuse has really
> exploded. Shattered glass in the fuse holder. A brief examination of the
> primary side of the smps reveals no shorts. The smps is an ordinary
> flyback supply. Mains rectifier ok, switch ok, snubber, line filters all
> ok. Really don't know why the mains fuse went.
> I just don't want to put a new fuse in and try again, not before I
> investigate the cause.
> Could an incorrect measurement setup cause the mains fuse to explode?
> Anyone familiar with these scopes or perhaps has a service manual for
> it?
> Best regards
> PAF

Flames out the back from an incorrect measurement set up? That would have
to have been one hell of a mistake.
From: powerampfreak on 13 Jun 2010 18:10
On 14 Juni, 00:04, Meat Plow <mhyw...(a)yahoo.com> wrote:
> On Sun, 13 Jun 2010 14:16:36 -0700, powerampfreak ǝʇoɹʍ:
>
>
>
> > I was given an oscilloscope, a Fluke PM3082 from a retired industrial
> > electronics engineer.
> > He said that during a measurement, the oscilloscope's powersupply just
> > bang and a flame came out of the rear panel. After this, the scope was
> > left for several years...until I got it. The mains fuse has really
> > exploded. Shattered glass in the fuse holder. A brief examination of the
> > primary side of the smps reveals no shorts. The smps is an ordinary
> > flyback supply. Mains rectifier ok, switch ok, snubber, line filters all
> > ok. Really don't know why the mains fuse went.
> > I just don't want to put a new fuse in and try again, not before I
> > investigate the cause.
> > Could an incorrect measurement setup cause the mains fuse to explode?
> > Anyone familiar with these scopes or perhaps has a service manual for
> > it?
> > Best regards
> > PAF
>
> Flames out the back from an incorrect measurement set up? That would have
> to have been one hell of a mistake.

I appreciate your wise input!
What I was thinking about, was if he in some way measured on mains
live net for some reason.
Like if he forgot to use the isolation transformer.
From: nesesu on 13 Jun 2010 18:29
On Jun 13, 2:16 pm, powerampfreak <powerampfr...(a)hotmail.com> wrote:
> I was given an oscilloscope, a Fluke PM3082 from a retired industrial
> electronics engineer.
> He said that during a measurement, the oscilloscope's powersupply just
> bang and a flame came out of the rear panel. After this, the scope was
> left for several years...until I got it.
> The mains fuse has really exploded. Shattered glass in the fuse
> holder. A brief examination of the primary side of the smps reveals no
> shorts. The smps is an ordinary flyback supply. Mains rectifier ok,
> switch ok, snubber, line filters all ok. Really don't know why the
> mains fuse went.
> I just don't want to put a new fuse in and try again, not before I
> investigate the cause.
> Could an incorrect measurement setup cause the mains fuse to explode?
> Anyone familiar with these scopes or perhaps has a service manual for
> it?
> Best regards
> PAF

I might suggest that you install a fuse that fits [the correct current
rating if possible, but not essential] and then do a 'Hi-pot' test
between the two mains prongs and the chassis/earth prong. It is quite
possible that in his test set-up that the earth prong was isolated
from earth and the 'scope chassis was raised way too far above earth
and caused a preakdown of the insulation betwixt the mains wiring and
earth internal to the 'scope. I would look particularly at the 'Y'
caps of the line filter since thay may have 'healed' after the fault
but could certainly have caused an explosion of the mains fuse if
there was sufficient power applied to the chassis from the test set-
up. An example could be measuring 550V or 600V non-isolated 3 phase
power where you might get >1000V between the chassis and 240V mains
power.
If such a thing happened, replacing the 'Y' caps [and fuse] might be
all that's required.

Neil S.
From: Meat Plow on 13 Jun 2010 18:42
On Sun, 13 Jun 2010 15:10:58 -0700, powerampfreak ǝʇoɹʍ:

> On 14 Juni, 00:04, Meat Plow <mhyw...(a)yahoo.com> wrote:
>> On Sun, 13 Jun 2010 14:16:36 -0700, powerampfreak ǝʇoɹʍ:
>>
>>
>>
>> > I was given an oscilloscope, a Fluke PM3082 from a retired industrial
>> > electronics engineer.
>> > He said that during a measurement, the oscilloscope's powersupply
>> > just bang and a flame came out of the rear panel. After this, the
>> > scope was left for several years...until I got it. The mains fuse has
>> > really exploded. Shattered glass in the fuse holder. A brief
>> > examination of the primary side of the smps reveals no shorts. The
>> > smps is an ordinary flyback supply. Mains rectifier ok, switch ok,
>> > snubber, line filters all ok. Really don't know why the mains fuse
>> > went. I just don't want to put a new fuse in and try again, not
>> > before I investigate the cause.
>> > Could an incorrect measurement setup cause the mains fuse to explode?
>> > Anyone familiar with these scopes or perhaps has a service manual for
>> > it?
>> > Best regards
>> > PAF
>>
>> Flames out the back from an incorrect measurement set up? That would
>> have to have been one hell of a mistake.
>
> I appreciate your wise input!
> What I was thinking about, was if he in some way measured on mains live
> net for some reason.
> Like if he forgot to use the isolation transformer.

One would assume that this would be an unlikely scenario but not that far
removed from reality. Anything is possible I suppose and your knowledge
and diligence will no doubt find an answer. I would try to stick with the
cold hard facts and not let speculation muddy the waters.
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