On 27/02/2014 14:17, Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
On 27/02/2014 10:07, Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:

Japanese stuff is always OK anywhere as they have half 50Hz UK and
half USA 60Hz frequency depending on which part of the country you
live in!

This was made in China.

What is interesting is the legend on the rear panel also shows 100v 60
Hz and 230v 50 Hz as choices - presumably with a different
transformer(s)?

Possibly. Maybe the same one and a different internal setting.

Not quite sure what you mean? On an analogue power supply, the mains input
is always set by tappings on the transformer.

There may be jumpers that can switch it from a series to parallel
winding configuration if that is what the maker intended. A lot of US
stuff tends to be cheapskate though and only work on local US mains.

Ronson electric shavers spring to mind as an example of a horrible
design that depended on a 60Hz mechanical resonance to work properly and
was useless in the UK. They pushed them very hard as Xmas presents.

No idea if their modern ones still have this problem but they did in the
1970's.

But this one was marked 120v 60 Hz and I can't see why they'd make the
transformer for that with two windings in parallel if couldn't be
altered to 240v.

The thing to watch out for is that it might only be safe under full load
when on 240v and 60Hz (the transformer needs ~20% less metal).

If they were cutting costs to the last fraction of a penny on components,
why use a dual winding transformer? Be cheaper to have a different one for
each and every voltage? And make assembly easier?

Depends how they cost their inventory.

Monitor it very closely for signs of overheating after conversion.

Bit difficult, that one.

LCD thermochromic label and check after a few hours use.

--
Regards,
Martin Brown