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I dislike ordering stuff that is not in stock



 
 
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  #11  
Old November 29th 16, 12:40 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
external usenet poster
 
Posts: 457
Default I dislike ordering stuff that is not in stock

On Monday, 28 November 2016 21:50:38 UTC, Scott wrote:
On Mon, 28 Nov 2016 21:02:06 GMT, pamela wrote:

On 14:52 28 Nov 2016, Phi wrote:

Twice recently I have tried to order a Sony smart TV listed by
Amazon for next day delivery, but it is eventually not
available. The latest delivery date now is 21st December so I
had to cancel. Argos, Hughes and Richersounds have the TV, but
only for in store collection.


I had a variation on this. The item I wanted from a UK vendor was in
stock but it was coming to me from their American supplier's
warehouse. Right now it's stuck somewhere in customs.


Hope it's not 110 Volts.


It depends. Sony stuff is voltage switchable and their warranties international, so you could personally import from the USA, however their ROB ration was low, so there was little point unless you were there and could bring gear back VAT and duty free in person. Yamaha OTOH made their gear region specific (so US amp's were 110V only) and would not honour warranties outside the country of purchase. Their ROB rate was 250%!
  #12  
Old November 29th 16, 02:03 PM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 297
Default I dislike ordering stuff that is not in stock

On 29/11/2016 13:40, R. Mark Clayton wrote:
On Monday, 28 November 2016 21:50:38 UTC, Scott wrote:
On Mon, 28 Nov 2016 21:02:06 GMT, pamela wrote:

On 14:52 28 Nov 2016, Phi wrote:

Twice recently I have tried to order a Sony smart TV listed by
Amazon for next day delivery, but it is eventually not
available. The latest delivery date now is 21st December so I
had to cancel. Argos, Hughes and Richersounds have the TV, but
only for in store collection.

I had a variation on this. The item I wanted from a UK vendor was in
stock but it was coming to me from their American supplier's
warehouse. Right now it's stuck somewhere in customs.


Hope it's not 110 Volts.


It depends. Sony stuff is voltage switchable ....


These days most (not all !) PSUs in consumer goods are SMPSUs with
a 80-250 volt 'window', aren't they ?


--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #13  
Old November 29th 16, 03:46 PM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,768
Default I dislike ordering stuff that is not in stock

On Tue, 29 Nov 2016 16:38:58 +0100, Martin wrote:
On Tue, 29 Nov 2016 15:03:04 +0000, Mark Carver

wrote:

These days most (not all !) PSUs in consumer goods are SMPSUs with
a 80-250 volt 'window', aren't they ?


Decades ago Panasonic in the Netherlands provided me with a free

multi standard
transformer so that I could convert to 230V, a Panasonic receiver

that I
imported from California.


Was it a clock radio? If so, it would have to convert the frequency
as well. For that matter, don't 60 Hz appliances tend to overheat on
50 Hz?

--
Max Demian
  #14  
Old November 29th 16, 04:19 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 7,562
Default I dislike ordering stuff that is not in stock

On 29/11/2016 16:46, Max Demian wrote:
On Tue, 29 Nov 2016 16:38:58 +0100, Martin wrote:
On Tue, 29 Nov 2016 15:03:04 +0000, Mark Carver

wrote:

These days most (not all !) PSUs in consumer goods are SMPSUs with
a 80-250 volt 'window', aren't they ?


Decades ago Panasonic in the Netherlands provided me with a free

multi standard
transformer so that I could convert to 230V, a Panasonic receiver

that I
imported from California.


Was it a clock radio? If so, it would have to convert the frequency as
well. For that matter, don't 60 Hz appliances tend to overheat on 50 Hz?


Yes, my Uncle used to be a field service engineer for Westinghouse,
fixing their kitchen appliances in posh-knobs' houses all over Surrey
and Sussex. Very common fault was the transformer
burning out on their microwave ovens, although there was a 240 volt
tapping for the primary, the American factory hadn't taken the
inductive reactance at 50 Hz into consideration.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #15  
Old November 29th 16, 10:08 PM posted to uk.tech.digital-tv
Ian Jackson[_5_]
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Posts: 42
Default I dislike ordering stuff that is not in stock

In message , Martin
writes
On Tue, 29 Nov 2016 17:19:30 +0000, Mark Carver
wrote:

On 29/11/2016 16:46, Max Demian wrote:
On Tue, 29 Nov 2016 16:38:58 +0100, Martin wrote:
On Tue, 29 Nov 2016 15:03:04 +0000, Mark Carver
wrote:

These days most (not all !) PSUs in consumer goods are SMPSUs with
a 80-250 volt 'window', aren't they ?

Decades ago Panasonic in the Netherlands provided me with a free
multi standard
transformer so that I could convert to 230V, a Panasonic receiver
that I
imported from California.

Was it a clock radio? If so, it would have to convert the frequency as
well. For that matter, don't 60 Hz appliances tend to overheat on 50 Hz?


Yes, my Uncle used to be a field service engineer for Westinghouse,
fixing their kitchen appliances in posh-knobs' houses all over Surrey
and Sussex. Very common fault was the transformer
burning out on their microwave ovens, although there was a 240 volt
tapping for the primary, the American factory hadn't taken the
inductive reactance at 50 Hz into consideration.


I can assure you that it didn't over heat. It could be that a receiver
uses less
power than a microwave oven. I suppose that it is possible that it was designed
for 50Hz and modified for the American market.


Doesn't some American high-power domestic equipment operate on 220V
(from two phases of a three-phase 120V supply)? Although 220V is within
the spec for a so-called 230V mains supply, there could still problems
if it used on 50Hz.
--
Ian
  #16  
Old November 30th 16, 06:56 AM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 297
Default I dislike ordering stuff that is not in stock

On 29/11/2016 23:08, Ian Jackson wrote:
In message , Martin


I can assure you that it didn't over heat. It could be that a receiver
uses less
power than a microwave oven. I suppose that it is possible that it was
designed
for 50Hz and modified for the American market.


Doesn't some American high-power domestic equipment operate on 220V
(from two phases of a three-phase 120V supply)? Although 220V is within
the spec for a so-called 230V mains supply, there could still problems
if it used on 50Hz.


Indeed they do, and given a 'but isn't the whole World 60Hz ?'
misconception, could well be the case.

Martin still seems to be grumpy after his eye op, I'm not suggesting
*all* American kit can't cope with 50 Hz, just that *some* seemed not to.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #17  
Old November 30th 16, 11:34 AM posted to uk.tech.digital-tv
external usenet poster
 
Posts: 265
Default I dislike ordering stuff that is not in stock

On Wed, 30 Nov 2016 12:36:55 +0100
Martin wrote:
On Wed, 30 Nov 2016 07:56:48 +0000, Mark Carver
wrote:

On 29/11/2016 23:08, Ian Jackson wrote:
In message , Martin


I can assure you that it didn't over heat. It could be that a receiver
uses less
power than a microwave oven. I suppose that it is possible that it was
designed
for 50Hz and modified for the American market.

Doesn't some American high-power domestic equipment operate on 220V
(from two phases of a three-phase 120V supply)? Although 220V is within
the spec for a so-called 230V mains supply, there could still problems
if it used on 50Hz.


Indeed they do, and given a 'but isn't the whole World 60Hz ?'
misconception, could well be the case.

Martin still seems to be grumpy after his eye op, I'm not suggesting
*all* American kit can't cope with 50 Hz, just that *some* seemed not to.



Why would 60Hz apparatus overheat on 50Hz? Surely it would be the other
way around since a higher frequency contains more energy for a given max
amplitude (in this case voltage)?

--
Spud

  #18  
Old November 30th 16, 12:13 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 457
Default I dislike ordering stuff that is not in stock

On Wednesday, 30 November 2016 12:34:32 UTC, wrote:
On Wed, 30 Nov 2016 12:36:55 +0100
Martin wrote:
On Wed, 30 Nov 2016 07:56:48 +0000, Mark Carver
wrote:

On 29/11/2016 23:08, Ian Jackson wrote:
In message , Martin

I can assure you that it didn't over heat. It could be that a receiver
uses less
power than a microwave oven. I suppose that it is possible that it was
designed
for 50Hz and modified for the American market.

Doesn't some American high-power domestic equipment operate on 220V
(from two phases of a three-phase 120V supply)? Although 220V is within
the spec for a so-called 230V mains supply, there could still problems
if it used on 50Hz.

Indeed they do, and given a 'but isn't the whole World 60Hz ?'
misconception, could well be the case.

Martin still seems to be grumpy after his eye op, I'm not suggesting
*all* American kit can't cope with 50 Hz, just that *some* seemed not to.



Why would 60Hz apparatus overheat on 50Hz? Surely it would be the other
way around since a higher frequency contains more energy for a given max
amplitude (in this case voltage)?

--
Spud


Most domestic electronics have switched mode supplies these days. Incoming mains is rectified, smoothed and then run through much smaller transformers at tens of hundreds of kHz.

These are pretty efficient and the PSU barely gets warm.
  #19  
Old November 30th 16, 12:54 PM posted to uk.tech.digital-tv
Ian Jackson[_5_]
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Posts: 42
Default I dislike ordering stuff that is not in stock

In message , d writes
On Wed, 30 Nov 2016 12:36:55 +0100
Martin wrote:
On Wed, 30 Nov 2016 07:56:48 +0000, Mark Carver
wrote:

On 29/11/2016 23:08, Ian Jackson wrote:
In message , Martin

I can assure you that it didn't over heat. It could be that a receiver
uses less
power than a microwave oven. I suppose that it is possible that it was
designed
for 50Hz and modified for the American market.

Doesn't some American high-power domestic equipment operate on 220V
(from two phases of a three-phase 120V supply)? Although 220V is within
the spec for a so-called 230V mains supply, there could still problems
if it used on 50Hz.

Indeed they do, and given a 'but isn't the whole World 60Hz ?'
misconception, could well be the case.

Martin still seems to be grumpy after his eye op, I'm not suggesting
*all* American kit can't cope with 50 Hz, just that *some* seemed not to.



Why would 60Hz apparatus overheat on 50Hz? Surely it would be the other
way around since a higher frequency contains more energy for a given max
amplitude (in this case voltage)?

Basically, a transformer requires enough inductance (inductive)
impedance or reactance) to stop it from shorting out the mains supply.

Consider a simple 1-to-1 transformer, 230V in, 230V out.

Ask yourself why it is the size it is.

The answer is that it has (say) 100 turns of wire on the primary, and
100 on the secondary. That takes up space.

Now ask yourself why it needs 100 turns. Why could it not simply have 1
turn on the primary and 1 turn on the secondary?

The simplistic answer is that a 1 turn primary could not, without
carrying a ginormous current, generate enough magnetic flux in the iron
core for the transformer to work.

A more accurate explanation is that a practical transformer can be
considered as having a primary which consists of two windings in
parallel. Winding 1 carries the current which transfers its power to the
secondary winding. Winding 2 carries the current required to generate
the magnetic field which facilitates the transfer - but otherwise any
current flowing in Winding 2 is wasted.

The important thing is that the inductive reactance of Winding 2 is
shunting the mains input, and at the frequency of the AC mains, the
reactance has to be high enough not to take too much current.

At frequency F Hz, the reactance of an inductor of L henries is 2 x pi x
F x L This means that the reactance increases with frequency (and vice
versa), so a reactance which is sufficient 60Hz might not be sufficient
for 50Hz. As a result, Winding 2 takes more current. This causes it (and
the whole transformer) to overheat, and is also likely to blow the mains
fuse.

--
Ian
  #20  
Old November 30th 16, 01:28 PM posted to uk.tech.digital-tv
external usenet poster
 
Posts: 265
Default I dislike ordering stuff that is not in stock

On Wed, 30 Nov 2016 13:54:57 +0000
Ian Jackson wrote:
A more accurate explanation is that a practical transformer can be
considered as having a primary which consists of two windings in
parallel. Winding 1 carries the current which transfers its power to the
secondary winding. Winding 2 carries the current required to generate
the magnetic field which facilitates the transfer - but otherwise any
current flowing in Winding 2 is wasted.


Eh? Without current in the primary winding there is no magnetic field or
current in the secondary. The secondary is purely passive surely?

The important thing is that the inductive reactance of Winding 2 is
shunting the mains input, and at the frequency of the AC mains, the
reactance has to be high enough not to take too much current.

At frequency F Hz, the reactance of an inductor of L henries is 2 x pi x
F x L This means that the reactance increases with frequency (and vice
versa), so a reactance which is sufficient 60Hz might not be sufficient
for 50Hz. As a result, Winding 2 takes more current. This causes it (and
the whole transformer) to overheat, and is also likely to blow the mains
fuse.


So you're basically saying for a lower frequency you need more wire in each
winding?

--
Spud


 




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