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UK to US step down Transformers and other things.

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UK to US step down Transformers and other things.

Postby Moroccomoose » Mon Apr 13, 2020 7:57 pm

I have an old Korg keyboard (A DS-8 if it matters)I use for my midi controller. It is configured for 110V so it also had a big wall wart step down transformer.

The wall wart transformer makes quite an audible hum. Should I replace it? I'd guess it is 30 or 40 years old.

A few weeks ago, someone posted a link to integrated IEC connector with power supply in a compact housing. Are they available for UK to US step down, or does the physics simply dictate that you need a massive wall wart transformer to do the job?

Any ideas for a nicer solution than a huge wall wart welcomed!

Stu.
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Re: UK to US step down Transformers and other things.

Postby James Perrett » Mon Apr 13, 2020 9:14 pm

Moroccomoose wrote:A few weeks ago, someone posted a link to integrated IEC connector with power supply in a compact housing. Are they available for UK to US step down, or does the physics simply dictate that you need a massive wall wart transformer to do the job?

Those produce low voltage DC so wouldn't be any good for what you want to do. It sounds like your transformer has some loose windings on it. Sometimes it is possible to reduce the noise by various kludges but it may be better to relegate the existing transformer to a less critical use ( where it will probably carry on working fine for years) and buy a new one.
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Re: UK to US step down Transformers and other things.

Postby James Perrett » Mon Apr 13, 2020 9:19 pm

I just had a quick search for a service manual for the DS-8 and came up with this one

https://www.synthxl.com/wp-content/uplo ... manual.pdf

which shows that the mains transformer has taps for both 120V and 240V. If yours has the same mains transformer it may be simpler to change the wiring so that the keyboard works directly from 240V.
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Re: UK to US step down Transformers and other things.

Postby Martin Walker » Mon Apr 13, 2020 9:23 pm

James Perrett wrote:It sounds like your transformer has some loose windings on it. Sometimes it is possible to reduce the noise by various kludges but it may be better to relegate the existing transformer to a less critical use ( where it will probably carry on working fine for years) and buy a new one.

Agreed - I've heard of people doing bizarre things such as soaking their transformers in a bath of molten wax to impregnate the laminations and stop vibration.

Sometimes even jamming some neoprene strips between the transformer and a surrounding case panel will dampen down any vibration between the two (this has worked for me in the past on an otherwise lovely-sounding power amp.

However, if a simple trick like this doesn't solve the current problem I agree with James that replacing the step-down transformer is probably the easiest solution.

EDIT: If you're happy with modifying mains wiring, then James' subsequent suggestion is by far the best option. Just don't forget to stick a new label on your gear to indicate that it's now wired for 240-volts :headbang:


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Re: UK to US step down Transformers and other things.

Postby Sam Spoons » Mon Apr 13, 2020 10:32 pm

It's probably better to plug 240VAC gear into a 120VAC supply that vice versa (don't ask me how I know :oops: .....)
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Re: UK to US step down Transformers and other things.

Postby Moroccomoose » Tue Apr 14, 2020 7:22 am

Thanks chaps this is very helpful. Although I'm no electrician, I can probably cope with swapping a transistor tap, so I may get surgical.

Assuming the change is possible, I don't have any test gear.... is there a safe way to test before committing 240V to it? Maybe still offer up the stepped down power afterwards before giving it the full beans?

So, seeing as the service manual is there and lockdown is giving me thumb twiddling time, I might just give it a full (mechanical) service while it's open.

If it's okay with you guys, I might just stick a photo up here once I have it open just to confirm that the change can be done and that I'm making the correct change. It'll likely be next weekend though.

Cheers all,

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Re: UK to US step down Transformers and other things.

Postby ef37a » Tue Apr 14, 2020 7:55 am

BIG! No-no about 'impregnating' transformers!

There are only certain compounds that are approved for use based on fire hazard, ever seen a WAX candle?

If changing the transformer tap involves moving wires, i.e. no selector switch then that really should be done by a qualified tech and the gear then PAT tested, it MUST be tested if you ever move it on.

I suggest you just buy a better step down transformer and from a reputable source such as RS Components or Farnell/CPC. I have read in a guitar/guitar amp forum that there are some badly made, potentially dangerous auto traffs about on the web.
I don't know what the consumption of that gear is but I would think a 100va transformer would be more than adequate?

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Re: UK to US step down Transformers and other things.

Postby Moroccomoose » Tue Apr 14, 2020 9:06 am

Hi Dave,

Thanks for the cautionary notes and they are noted.

To put your mind at ease, if it was otherwise..

I shan't be tampering with the wall wart. If I stay with a step down, I'll replace it.
I'm pretty clear what my ability is with a soldering iron, and I'm naturally risk averse so if it's anything other than obvious and simple, I'll be back to plan B and replace the wart. But the inside will at least have had a good dusting!
It is almost inconceivable that it would ever be moved on. I'm a bit of a hoarder in that respect!

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Re: UK to US step down Transformers and other things.

Postby ef37a » Tue Apr 14, 2020 11:26 am

Actually this...https://www.amazon.co.uk/240v-110v-Step ... p_pl_dp_13

Looks very suitable. I like the plastic case rather than metal since even if the internals are a complete FU you won't get a shock! Doubt that they are since Amazon are pretty picky.

I did have a quick look on the RS and Farnell sites and could not find anything really suitable but then they do have an awful lot of them!

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Re: UK to US step down Transformers and other things.

Postby Moroccomoose » Tue Apr 14, 2020 11:46 am

Cheers Dave,

I'll check RS etc. That Amazon one looks a bit over kill though! The keyboard draws 18W and the wart I have is rated 45 watts.

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Re: UK to US step down Transformers and other things.

Postby Trevor Johnson » Tue Apr 14, 2020 12:03 pm

Well found Dave. The Amazon 300W is made by Mercury and I note that CPC also sell Mercury and there is a 100W version costing £20.16 in VAT and shipping. Since it weighs 1.5Kg it won't be a wall-wart either. May be worth looking at.

https://cpc.farnell.com/mercury/651-004uk/step-down-converter-100w-230v/dp/PW04236
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Re: UK to US step down Transformers and other things.

Postby ef37a » Tue Apr 14, 2020 2:35 pm

Trevor Johnson wrote:Well found Dave. The Amazon 300W is made by Mercury and I note that CPC also sell Mercury and there is a 100W version costing £20.16 in VAT and shipping. Since it weighs 1.5Kg it won't be a wall-wart either. May be worth looking at.

https://cpc.farnell.com/mercury/651-004uk/step-down-converter-100w-230v/dp/PW04236

An even better find Trev'! did not know the gear pull was that low but in any case it pays to have transformers well over rated since it is when they are loaded up that they buzz and put out a stronger field.

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Re: UK to US step down Transformers and other things.

Postby nathanscribe » Thu Apr 16, 2020 2:15 pm

Just to add, don't forget to check that your step-down is earthed if required. I had some cheap 45W ones that a) were not earthed on the UK mains side, although they had a ground pin hole on the 110/120V side, and b) they were crap! They'd conk out when run anywhere above maybe half their nominal rating. Never again.
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Re: UK to US step down Transformers and other things.

Postby N i g e l » Thu Apr 16, 2020 7:29 pm

ef37a wrote:BIG! No-no about 'impregnating' transformers!

There are only certain compounds that are approved for use based on fire hazard, ever seen a WAX candle?
.

The substance to use is "conformal coat" a high temperature insulating varnish for circuit boards to make them moisture resistant. Can be dipped or brushed on.

Ive never de-hummed a transformer myself but if you ask on the NORD forum you may get some advice. ;) :shh:
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Re: UK to US step down Transformers and other things.

Postby Folderol » Thu Apr 16, 2020 7:55 pm

Sometimes it can be as simple as tightening the bolts!
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