Ducati Sporting Club UK > General > Idle Chat > Any Electrician Type Gurus Out There???

[Ian Harris]

I'm looking for a bit of advice on an electrical matter of absolutely no relevence to Ducatis at all, but thought I would post it up here having seen a miraculous amount of information being provided on several previous obscure posts. ...

I'm in the process of importing a set of Chinese valve amplifiers, which need to run at 220 volts.

The only thing I've come up with so far (apart from completely replacing the power supplys) is to use a variable voltage transformer such as:

http://www.coleparmer.co.uk/catalog/...0157515&pfx=EW

Can I wire the out put of one of these to a four-way socket to power my amps? Alternatively, has anyone got any other suggestions (beyond just making do with an Ipod).


Thanks in anticipation!

[skidlids]

Thats a bit pricey

http://www.maplin.co.uk/Module.aspx?...ME R&doy=27m7

I had to replave a variac at work today, yes you could power a multi block from one and vary the voltage.

I'm not sure a SCR device as found in many light dimmers would do the job with amps as the load as the way they chop the incoming mains may come through on the amp as noise

So I would probably go with the variac

[Ian Harris]

Kev,

Many thanks for that... I looked at SCR devices, but concluded that they'd ****** up the supply. One more question...do you reckon getting a 2nd hand variacs worth while? I've seen one on ebay which would mean I wouldn't have to build a case for a Maplin's one

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA%3AIT&rd=1

Thanks again, Ian

[FiscusFish]

As UK voltage is "supposed" to be 230V +10%/-6% (according to google) should they not work ok as standard without the need for an additional transformer?

[skidlids]

Second hand ones are OK if youi get one with a good condition carbon brush in the wiper, the one I replaced yesterday was a previously used one and it worked for all of a week. I replaced it with a newer one that has had hardly any use and have since found a spare brush for the one that failed

I had one of the shift electricians build me a control unit the other day to vary the heater power on our electron guns when testing them. All that is needed is a box, ideally a voltmeter (we also added a ammeter to the O/P side) an illuminated rocker switch for mains ON/OFF (we also added a switch to the O/P with a indicator lamp as the unit is interlocked to thw water cooling and vacuum) The mains in and O/P leads are by way of stuffing glands. So you should be able to build a 8 amp one for around £100.

If you can find a cheap one on ebay in good condition then go for it, do you know the sort of current you need.

[skidlids]

Just looked at the Ebay one Ian, that looks the same as the one I fitted yesterday and at 11.5 amps should be worth trying if it can be had for the right price

[phil_h]

fiscus is right about the voltage spec - 230Vac is pan-european now.
Check the spec on your valves : 230V is 220V + 4.5%
and ... you dont say how much power they consume - which is a rather important factor if you want to drive them through any kind of intermediate device. Almost everything you put in the way will get hotter than you would like, especially if its cheap far-eastern stuff, as their manufacturing policy seems to be to see what they can get away with, and then charge you an arm when you come back with a tighter (reasonable) spec.

[Ian Harris]

Originally Posted by FiscusFish

As UK voltage is "supposed" to be 230V +10%/-6% (according to google) should they not work ok as standard without the need for an additional transformer?

I think "supposed" is the operative word here! Basically, we still have a 240 volt supply, Europe still has a 220 volt supply and the +10% / -6% allows Europe to be theoretically "harmonised" without anyone changing anything.

I've no doubt that the amps would work, but considering the delicate nature of valves and the voltage that is going through them, I would rather get the input voltage right rather than have an almighty bang on start up one day.

[Ian Harris]

Originally Posted by phil_h

aand ... you dont say how much power they consume - which is a rather important factor if you want to drive them through any kind of intermediate device. Almost everything you put in the way will get hotter than you would like, especially if its cheap far-eastern stuff, as their manufacturing policy seems to be to see what they can get away with, and then charge you an arm when you come back with a tighter (reasonable) spec.

Power consumption is about 210 watts at 220 volts per amp...this will be fairly constant, as they are class A (meaning they always run at full blast, irrespective of how much sound is coming out)...does that make it about 1amp ??? I'm hoping 2amp plus a tiny bit more for the pre-amp will not create too much heat in the additional transformer.

As for quality...this is a bit of a gamble, ... I believe the stuff I am buying is pretty near to US / American standards of construction, but it definitely has 220 volt power supplies (which suit Europe fine, but sadly not us in the UK). The gear I am buying does not currently have a formal UK importer, so is not available with 240 volt freindly supply. If its good stuff, I'll upgrade components in due course...if its not, I'll live and learn and stick it on ebay with a suitably realistic description.

[Ian Harris]

Originally Posted by skidlids

Second hand ones are OK if youi get one with a good condition carbon brush in the wiper, the one I replaced yesterday was a previously used one and it worked for all of a week. I replaced it with a newer one that has had hardly any use and have since found a spare brush for the one that failed

Ahh...so its that old ebay thing "buyer beware"....I'll have a think whether to cobble one together from one of the Maplin ones...As per above post, total power demand should be 210watt @ 220 volt * 2 plus a tiny bit from the preamp...say 500 watt @ 220 volt ...would that be 2-3 amps???