100v supply for UK usage?

[coolin]

I've been given a 'faulty' Sony HCD S50C hifi to fix by a foreign student. I'm in the UK.
The power cable terminates in a 2-pin connector and from the text on the back of the unit, it's rated 100v.

I'm thinking this has been brought in from another country and so won't function on a 240v uk supply. The fuse on the transformer is intact.

However, it looks to me like the pcb on the transformer has extra, unused holes drilled and copper tracks connected for an alternatively located fuse and UK wiring.

Can anyone confirm the likelihood of this, and maybe help identify how it should be wired?

Sorry, this isn't really a typical repair as much as it is a modification.

 

[davenn]

hi there
welcome to the forums

not really enough info to give a good answer
how about some pics of that part of the PSU board so we can see what you were referring to

cheers
Dave

 

[duke37]

Equipment intended to be used in various countries often has a transformer with two primary windings which can be connected in parallel for 110V or series for 220/240V. The specification should be found since changing from 60Hz to 50Hz will also have an effect.

I recently sorted out a ghetto blaster which had been brought in from the US and plugged staight in. The transformer was killed so I fed DC from a wall wart to the battery compartment.

 

[coolin]

pics of pcb

Okay, here's the circuit board top and bottom.

L and N are where the 2-pin power cable connects presently.

I can see accommodation for a wire jumper at JW804 and a fuse at F802.

The yellow rectangle indicates where I think a 240v supply would connect. Precisely how, well, that's why I'm here!

Thanks for any help you can offer.

 

[coolin]

Okay, I'm going to remove the jumper at JW800 and make JW804. I shall also move the fuse holder (and fuse) to F802.

As I'm looking at the pcb now, I've had a thought: would there be a situation where both the 'original' terminal at 100v AND the alternative connection is made? I'm wondering if, rather than moving the fuse & holder I should be adding in a second & a jumper so that both terminals to the transformer get 240v?

 

[duke37]

You can keep the amp at low voltage with its normal input lead and use an external tronsformer, an 80V transformer will give compensation for a change from 60Hz to 50Hz. If you make internal modifications, then you will need to fit a standard UK lead.

Are there two primary windings? Check their resistance when disconnected.
Make your modifications and measure the resistance across the mains plug, it should be equal to the two windings in series.
Energise with a 40W bulb in series with the supply in case you have the phase wrong. If the bulb lights brightly, the current will be limited so damage MAY be averted.
If all looks well then energise directly but check temperatures of the power supply components.

I do not like the idea of using a 100V amp doubled to 200V on the UK mains which can rise to 253V and probably will be on a lower frequency. If there is a battery option, that is the way to go with a suitable power pack.