** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold in the
USA and Japanese markets is now regularly turning up in Australia. USA items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny will be
suitable. The modifications involve removing or shifting PCB links, altering
QC connectors or rewiring the supply side leads to the AC tranny - PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the back
and markings that indicate the possibility of 120V and 230/240V operation.

The unit has a toroidal tranny fitted inside with four supply side wires, so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and used a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries were
wired out of phase. No real harm done and a few minutes later I had the four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound the
variac up in gradual steps to 240V and suddenly and there was a very loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) - but
that is a DC voltage rating. So when exposed to a 240VAC supply with 340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being 275VAC,
as is the case with the class X2 cap wired in parallel.


..... Phil

Phil Allison wrote:
** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold in the
USA and Japanese markets is now regularly turning up in Australia. USA items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny will be
suitable. The modifications involve removing or shifting PCB links, altering
QC connectors or rewiring the supply side leads to the AC tranny - PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the back
and markings that indicate the possibility of 120V and 230/240V operation.

The unit has a toroidal tranny fitted inside with four supply side wires, so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and used a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries were
wired out of phase. No real harm done and a few minutes later I had the four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound the
variac up in gradual steps to 240V and suddenly and there was a very loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) - but
that is a DC voltage rating. So when exposed to a 240VAC supply with 340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being 275VAC,
as is the case with the class X2 cap wired in parallel.


.... Phil


Just about every device I've ever hand my hands on that allowed such
configuration had 2 MOV's, each rated for the lower voltage. When you
properly configure the connections on the board for 200+ volts for
example, the 2 MOV's end up in series, otherwise, they end up in
parallel for low voltage configuration.

Maybe some one has serviced that unit in the past and replaced them
incorrectly.

Jamie

"Jamie"

Just about every device I've ever hand my hands on that allowed such
configuration had 2 MOV's,


** There was ***ONE** only MOV wired across the pins of the IEC inlet.

****head.


..... Phil

Phil Allison wrote in message
...

** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold in
the
USA and Japanese markets is now regularly turning up in Australia. USA
items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny will
be
suitable. The modifications involve removing or shifting PCB links,
altering
QC connectors or rewiring the supply side leads to the AC tranny - PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the back
and markings that indicate the possibility of 120V and 230/240V operation.

The unit has a toroidal tranny fitted inside with four supply side wires,
so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and used
a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries
were
wired out of phase. No real harm done and a few minutes later I had the
four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound the
variac up in gradual steps to 240V and suddenly and there was a very loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) -
but
that is a DC voltage rating. So when exposed to a 240VAC supply with 340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being
275VAC,
as is the case with the class X2 cap wired in parallel.


.... Phil




Ever come across Crate (not some mickey mouse operation) USA "made" amps ,
for export to 240V countries , with mains switches + neons?
Neons glowing like lighthouses and melting all around, from the charring of
the droppers which are set for 110V including stating so on the switch
bodies

Yesterday had a somewhat related 110/240V repair but this time not safety
issue.
Little PV practise amp , 20W, original PV , properly set up for 240V , mains
fuse inside had "blown" at switch on.
1.25 inch F rated 250V 500mA . Maybe all right for 110V areas but repeatedly
switching on with the random occassional 330V surges and it will fail
mechanically (filament laying nicely diagonally in the barrel, fixed at one
end only).
T 500mA one went in there

"Nutcase Kook"
Yesterday had a somewhat related 110/240V repair but this time not safety
issue.
Little PV practise amp , 20W, original PV , properly set up for 240V ,
mains
fuse inside had "blown" at switch on.
1.25 inch F rated 250V 500mA . Maybe all right for 110V areas ..


** Surge and running currents are DOUBLED with 120V supplies.

The max peak ( switch on) surge can be estimated by measuring the resistance
of the primary winding of the AC tranny and dividing that number into the
supply voltage.

Eg:

The PV " Encore 65" tranny has a 7 ohm primary, the amp draws 0.25A rms at
idle and 1A rms at full tilt. The max inrush surge is however over 30
mps - so the AC supply use needs to be rated at " T3A " merely to survive
the surge.

In virtually essential to use a "delay" or " slo-blo" fuse with transformers
and SMPS. Unfortunately, the ****heads at PV and Fender do not comprehend
the issue and refuse to be informed on the matter.


.... Phil

N_Cook wrote:
Phil Allison wrote in message
...

** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold in
the
USA and Japanese markets is now regularly turning up in Australia. USA
items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny will
be
suitable. The modifications involve removing or shifting PCB links,
altering
QC connectors or rewiring the supply side leads to the AC tranny - PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the back
and markings that indicate the possibility of 120V and 230/240V operation.

The unit has a toroidal tranny fitted inside with four supply side wires,
so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and used
a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries
were
wired out of phase. No real harm done and a few minutes later I had the
four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound the
variac up in gradual steps to 240V and suddenly and there was a very loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) -
but
that is a DC voltage rating. So when exposed to a 240VAC supply with 340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being
275VAC,
as is the case with the class X2 cap wired in parallel.


.... Phil




Ever come across Crate (not some mickey mouse operation) USA "made" amps ,
for export to 240V countries , with mains switches + neons?
Neons glowing like lighthouses and melting all around, from the charring of
the droppers which are set for 110V including stating so on the switch
bodies

I've noticed quite a bit of dubious pilot lamps on equipment that should
allow 240volt export use. Luckily it's 120 here, so I've not have the
pleasure of experiencing what really happens with those.

Cydrome Leader wrote in message
...
N_Cook wrote:
Phil Allison wrote in message
...

** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold
in
the
USA and Japanese markets is now regularly turning up in Australia. USA
items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny
will
be
suitable. The modifications involve removing or shifting PCB links,
altering
QC connectors or rewiring the supply side leads to the AC tranny -
PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the
back
and markings that indicate the possibility of 120V and 230/240V
operation.

The unit has a toroidal tranny fitted inside with four supply side
wires,
so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and
used
a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries
were
wired out of phase. No real harm done and a few minutes later I had the
four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound
the
variac up in gradual steps to 240V and suddenly and there was a very
loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black
deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) -
but
that is a DC voltage rating. So when exposed to a 240VAC supply with
340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being
275VAC,
as is the case with the class X2 cap wired in parallel.


.... Phil




Ever come across Crate (not some mickey mouse operation) USA "made" amps
,
for export to 240V countries , with mains switches + neons?
Neons glowing like lighthouses and melting all around, from the charring
of
the droppers which are set for 110V including stating so on the switch
bodies

I've noticed quite a bit of dubious pilot lamps on equipment that should
allow 240volt export use. Luckily it's 120 here, so I've not have the
pleasure of experiencing what really happens with those.


Neoned rocker switches. After being on for ten minutes or more, the switch
is too hot to keep a finger on it. The little neon is glowing as bright as a
1W filament lamp, and the lens over it has a brown patch. Go inside inside
and melted plastic around the neon and the dropper which by now is a
blackened cylinder with a helix, certainly no colour markings

Cydrome Leader wrote in message
...
N_Cook wrote:
Phil Allison wrote in message
...

** Hi,

mainly due to the popularity of Ebay, electronic gear originally sold
in
the
USA and Japanese markets is now regularly turning up in Australia. USA
items
are intended for a 120V, 60Hz supply while Japanese ones are for 100V,
50Hz.

Conversion to 240V mains operation involves internal inspection and
modifications OR simply determining what VA rating step-down tranny
will
be
suitable. The modifications involve removing or shifting PCB links,
altering
QC connectors or rewiring the supply side leads to the AC tranny -
PLUS
changing fuses and the AC plug to the Aussie version.

I had an EVENT active studio monitor (twin port model) in for such
conversion this week and it looked easy. There is an IEC inlet on the
back
and markings that indicate the possibility of 120V and 230/240V
operation.

The unit has a toroidal tranny fitted inside with four supply side
wires,
so
it was of twin primary design allowing 120V and 240V operation. I
reorganised the four QCs according to a pattern drawn on the PCB and
used
a
variac to raise the voltage.

At about 30V, the ( T4A ) PCB fuse blew - indicating the two primaries
were
wired out of phase. No real harm done and a few minutes later I had the
four
wires the right way around.

Variaced the unit up again ( to about 130V ) and this time it started
working, I verified the woofer and tweeter were both OK. Next I wound
the
variac up in gradual steps to 240V and suddenly and there was a very
loud
BANG !!

All sound stopped. WTF !!!

When I opened the unit again there was a smoke inside and black
deposits
visible on the PCB and the nearby acetate filling used in the box. The
source was a 20mm varistor on the PCB that had exploded.

But why?

Markings on the part showed that it was rated for 270 volts ( 20K271) -
but
that is a DC voltage rating. So when exposed to a 240VAC supply with
340V
peaks it was grossly overloaded.

The stupid " Ying Tongs " had fitted the WRONG varistor.

The correct part is a 430 volt rated varistor OR one marked as being
275VAC,
as is the case with the class X2 cap wired in parallel.


.... Phil




Ever come across Crate (not some mickey mouse operation) USA "made" amps
,
for export to 240V countries , with mains switches + neons?
Neons glowing like lighthouses and melting all around, from the charring
of
the droppers which are set for 110V including stating so on the switch
bodies

I've noticed quite a bit of dubious pilot lamps on equipment that should
allow 240volt export use. Luckily it's 120 here, so I've not have the
pleasure of experiencing what really happens with those.


Neoned rocker switches. After being on for ten minutes or more, the switch
is too hot to keep a finger on it. The little neon is glowing as bright as a
1W filament lamp, and the lens over it has a brown patch. Go inside inside
and melted plastic around the neon and the dropper which by now is a
blackened cylinder with a helix, certainly no colour markings