What to do about owning a 220V amp in a 240V environment?

[Random Hero]

Yo guys, i'm new here, as you can tell.

Anyways, I recently bought a Mark IV from Italy, and it's wired for 220V. UK power is officially 230V, the same as the rest of the EU, however, it's actually closer to 240V. Has anyone ever ran a 220V appliance in the UK?

I've looked into a few things, notably getting a voltage regulator such as the APC model, take what's coming out of the wall down to 220V.

Any other ideas before I go hacking the plug off and putting another on the end of the power cable.

Thanks

[John Phillips]

I could be wrong (it's a while since I saw inside one) but if this is a Mesa MkIV, I think it should have the correct voltage taps on the PT. They're only accessible inside, and you have to unsolder some wires from the power supply circuit board. Be careful, because on the Mesas with the 'Bold' and 'Spongy' or a 'Tweed Power' setting, there are two wires that need to be moved. They're marked in print on the PCB though, so any competent tech should be able to do it for you.

It isn't a good idea to just run it at the wrong voltage - as you correctly guessed, although in theory European voltages have been 'harmonized' at 230V, what's really happened is a change of definition of the voltages, and ours in the UK is still really 240 (and the rest of Europe is still 220). The difference is that they've just changed the tolerance limits so they appear to match. It's not a problem for most equipment since the internal voltages are stepped down, and regulated - so any differences are either much reduced or removed entirely. But a tube amp steps the voltages up, and in some cases this could exceed the ratings of components.

A shop I work in is very close to the local substation, and I measured 254V at the wall there once (while tracing what seemed to be an unusually high voltage in an amp)... bad enough on a 240V amp, but if applied to a 220V amp with a normal plate voltage of 450-475V, that would produce 520-548V, which is well above the rating of most filter caps, and I would definitely think not safe.

[Random Hero]

Thanks for the reply John. Yes, sorry, it's a Mesa Mark IV. So you wouldn't recommend running the amp with a voltage regulator either? What would concern me is if we are, as you rightly say, getting enormous voltages from the wall sometimes, I would expect it can't be too safe to run a Voltage Regulator at 230V, if there's say, 245V coming out of the wall?

Finding a competent tech around here could be a hassle... how much do you expect the work would cost, and how long would it take?

[John Phillips]

If it does have the right taps and points, half an hour maximum - probably half that even including testing it afterwards. Most techs will still charge a minimum of half an hour's worth of bench time though :). No parts required, so if it was any more than about £25-£30 I would look elsewhere.

A voltage regulator might be an option, or maybe a step-down transformer, but you'll need a big one for that power of amp - at least 300W (300VA) and preferably 500W... heavy and expensive. Converting the amp is much better really.

[Random Hero]

Oh yeah for sure. I've seen some 500 - 1000W step-downs floating around, but none that seem to do 240V down to 220V. Have I been looking in the wrong place?

The voltage regulator I saw had 1200VA apparently, but it seemed to be for office equipment and home electronics more than anything else... I've also seen 240V --> 120V for using US amps here around £50-£60, but never anything that does from UK voltage to EU voltage.

If at all possible, could you point me in the direction of some suitable transformer equipment, and I will look into getting the amp converted in the long run.

Thanks.

[John Phillips]

Some of the 240-120V stepdowns also have 220V taps - designed to do 220-120, but since they're simple auto-transformers (one winding with multiple taps) there's no reason you can't rewire them for 240-220. I had one recently but unfortunately I've just sold it...

I had a thought though - since the amp has a Tweed Power switch, just run it like that :). The way both this and the Bold/Spongy switch on the Dual Rectifiers works is to simply have an extra winding on the PT that simulates running with a Variac turned down a bit - so setting it to Tweed with a 240V input should be fine.

[Random Hero]

Interesting. I could run it just on tweed I suppose. This is perfectly safe?

I am calling up Mesa tomorrow too to get their take on it (i'm looking to get as many opinions as possible on the matter).

Btw, one of the regulators someone said I could use was this;
http://www.techstore.co.uk/browse.php?a=p&prodLineID=98299

It looks like it would mean I would have to wire a female kettle lead connector onto the amp's power lead but I shouldn't imagine that that's a tough job.

Good/bad idea?

[Random Hero]

I should add, I was thinking of using the regulator at 230V, rather than right down at 220V.

If that regulator looks like a bad idea, how easy would it be to rewire a 240-120V transformer? I simply don't trust local techs, to be honest. I've seen what some of them have done to other people's gear.

[Random Hero]

Anybody got any idea on those things I said above?

[Random Hero]

I thought I might give an update on this thread...

The amp came in about a week after this thread was initially posted. I've ran it mainly in Tweed mode, and now and again in Full Power. I'm still to find a suitable tech who I trust to do the work, so I'm stuck in this situation atm.

Another thing, I asked the guy I bought it from who did the work originally (It was bought from the US) and he gave me this company in Italy. So I e-mailed them asking what they would normally change a US amp to, and they said usually 230V.

Either way, the amp sounds terrific. Still unsure as to what to do about the Full Power thing really, but meh!

[MyVette67]

The way both this and the Bold/Spongy switch on the Dual Rectifiers works is to simply have an extra winding on the PT that simulates running with a Variac turned down a bit - so setting it to Tweed with a 240V input should be fine.
Hey John... I dont have a lot of knowledge as far as transformers and windings go but would a variac do the job?

It could be dialed down to 220V no matter where the amp is used with higher house voltage :confused:

Just a thought.

[Random Hero]

I actually have a picture of the inside of a IV chassis. I think i can see where the taps are. It says something like "For Tweed use T1, or T2". I can't really remember without looking again.

I suppose I could always open my own up and see how it really is wired, although I never have. Is it just a case of soldering the wires to the correct points?

EDIT: Here's the pic

http://img.photobucket.com/albums/v515/RandomHero12/p51102292zt.jpg

It actually says "Switch for Correct Tweed"

[John Phillips]

Yes - look at the left-hand end of that circuit board, and you can see both a 240 or 230V (I can't quite see the script, it's hidden by the cap band) connection and a 220V connection. All you have to do to set it for 240V is to move the wire from the 220V to the 240V - the Tweed connection doesn't need changing, it's T2 for both - which confirms what I thought about it being safe to run in Tweed on 240 :). (T1 is the Tweed connection for either 100 or 117V.)

It looks like the wires are connected under the board (I can't remember, it's so long since I've been inside a MkIV), but lifting the board should be a simple matter of squeezing the clips on the four nylon standoffs and pulling it up.

[Random Hero]

John, thanks again for your help.

Here's another picture. So how many wires of these need moving?

http://img.photobucket.com/albums/v515/RandomHero12/mark4_quilt_chassis1_lg.jpg

[Random Hero]

:)!