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 Forum index » Instruments and Equipment » Metasonix
Wretch outside the states, power supply
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EdisonRex
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Joined: Mar 07, 2007
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PostPosted: Wed Mar 07, 2007 4:02 pm    Post subject: Wretch outside the states, power supply Reply with quote  Mark this post and the followings unread

Hi.

I have Wretch s/n 024. It's kind of like owning a pit bull puppy, people look at you weird, especially when they hear the instrument. I am quite fond of it.

So anyway, I think I'm killing the power supply, and I'm not doing anything except using the instrument. Over here in the UK, where I live, the power isn't like the US, it's double strength, and a little slower in cycles. Back a while ago when I moved here I found that some equipment just wasn't cut out for 50Hz, even if I was converting the voltage. I had to get rid of a nice QSC amp, for example, because it kept popping it's circuit breaker.

The transformer for the Wretch seems to be in this category, except without the circuit protection. It gets real hot - did I say hot? I mean like melt the plastic hot. It's all deformed now. I suppose it adds to the character. But it's gonna fail and then I'll be off warranty, because it says in the manual that Eric requires us in 240V-ville to use step down transformers.

Now I wasn't born yesterday, or even in the 80s. So I know what 12 volts alternating current is, and since I happen to be a facility manager as part of my real life job, and an engineer too, I know it's actually rather easy to come up with 12VAC, >50VA as a secondary voltage. Most low power lighting in Europe uses 12VAC as the supply. So anyway, before I take a chance on preventing a fire in my studio when this wall wart melts down, I was wondering if any other UK or European users of the Wretch (are there any?) have solved this problem. Yeah, I'll call Eric too. Just thought I'd ask here first.

Last edited by EdisonRex on Sat Mar 10, 2007 5:11 pm; edited 1 time in total
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EdisonRex
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PostPosted: Sat Mar 10, 2007 4:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well, good thing I left the power supply on the window sill in front of the window. I've been working all day on this Wretch, and suddenly there's a little flash by the window, a PFFT and there's the smoke genie, and the Wretch has stopped playing. Quelle horreur!

The supply (MG Electronics MGT1240) is rated 120VAC 60 Hz .48A secondary 12VAC 40VA (3.3A). Having been an expat for almost 9 years now, that lack of a "50" is not a good sign for a power transformer. They really and truly do not like 50Hz.

Anyway, I sourced a Block HIT 60 which is probably a bit oversized (I don't mind), wasn't too expensive (£25) and is already running almost cold, where the old one had a hot spot on one side within 10 minutes.

Anyway, since the power supply blowing up didn't burn down my studio, and the new power supply works great, I'll bet I didn't void my warranty. Smile

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ian-s



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PostPosted: Sat Mar 10, 2007 4:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

A halogen transformer, what a great idea.

The whole 50/60 thing, I am told, is due to mechanical resonance.
The transformer physical design is supposed to minimise vibration at the intended frequency. So a 60Hz design will work at 50Hz but probably have a shorter life.
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EdisonRex
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PostPosted: Sat Mar 10, 2007 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

g2ian wrote:
A halogen transformer, what a great idea.


Thanks! I thought they'd be just the ticket.

g2ian wrote:

The whole 50/60 thing, I am told, is due to mechanical resonance.
The transformer physical design is supposed to minimise vibration at the intended frequency.


That makes sense. I probably should read up on the real cause since I've seen it so much.

g2ian wrote:

So a 60Hz design will work at 50Hz but probably have a shorter life.


This wall wart lasted approximately 22 hours running time, total.

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Parker: Like, old and outdated.


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EdisonRex
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PostPosted: Mon Mar 12, 2007 2:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Reading up on the phenomenon of 60Hz power supplies committing hari kari on 50 cycle power. It's well known.

This warning should be enough to look for the 50/60Hz label. But that's just first order thinking. There is even anecdotal evidence, not mine.

If resonance is the issue, it is that the resonance (L) becomes too high resulting in too much current (I). Which seems to make too much heat! This of course makes sense, since more current will make more heat in a transformer. They are not only reactive but they are resistive.

It seems that stepping voltage down further (90 volts) will reduce the resonance, which makes sense. But this is impractical. You can't get 90V supplies, or step down transformers.

Nope. Makes the most sense to source the right transformer. My oversized halogen transformer seems to be doing the trick nicely, the Wretch is actually more stable the past day, maybe I shut the window and that's helping too, but what do I know.

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Parker: Like, old and outdated.


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