Question for amp experts re mains voltage.

[Lucifuge]

So... mains voltages are theoretically standardised across the EU at 230V +/- 10%.

But we all know that the UK power supply was not actually changed and still runs at 240V, presumably +/- some percentage, as it can be higher near to a distribution station.

I've seen a few things about modifying or rebiasing valve amps because they might run too hot at 240V if they're actually designed for 230V.

There is also this note on the Hughes & Kettner website that they manufacture the Tubemeister in a specifice 240V version for the UK. However, I have never seen this from any other major amp manufacturer, even UK manufacturers like Marshall just specify 230V

The question is, does it matter and will running an amp that is designed for the generic 230V risk damaging it or shortening the life of the valves?

[jpfamps]

You have made a very good point here.

For clarification, the old UK standard was 240 V +6%/-10%.

Our old standard fits conveniently into the "new" harmonized EU standard, so we actually haven't had to change our mains at all, and it's still 240 V.

The upper limit of both standards is 253 V, and all equipment for sale in the EU should have been tested for operation at this voltage.

Of the major manufacturers, Fender acknowledge this. Look at the schematic for any of their amps (freely available from the Fender website), and they show mains transformer wiring of their export models for 230 V, and 240 V (230 UK).

Incidentally, all the Fender amps I see are wired to 230 V. I always rewire these for 240 V operation. This reduces the voltages in the amp, and make it run cooler.

Most other manufacturers don't have as many taps on their transformer primaries as Fender so if they want to accommodate EU and US voltages they will have two windings of 115 V, which can either be wired in parallel for 115V operation of series for 230.

[Frank]

Been a while since I stuck a meter across the mains and actually tested what's coming out of the wall but mains voltage can vary quite a bit during the day. Test it at 4am and you'll probably get a higher reading than when everyone's got the telly on to watch Corrie.

Playing about with PSU Designer, a transformer with a 230 Volt primary and 600 Volt secondary will produce 626 Volts when fed 240 Volts. Doesn't sound too drastic until you look at the voltages at the first filter cap which rises from just over 800 Volts to 850 Volts so yes, maybe it is a good idea to use that 240 Volt transformer tap.

Thinking about it a bit more, the bias supply would be affected too so wouldn't a fixed bias amp naturally bias colder?

[Toe-Knee]

Im ne of the unlucky few that has dodgy mains.

My average is 250v but sometimes gets up to around 260v.

I've complained about this and they said there's nothing they can do about it due to the power requirements in the city centre.

[jpfamps]

Mains in our workshop is 245 V during the day, and rises to just under 250 in the evening (we're not really in a residential block).

You're correct the bias will track the HT as the mains goes up and down, however the valves will be biased hotter at the higher HT.

Fender amps such as the Blues Junior which are biased hot anyway, then the extra voltage will push the valves even further over spec. Added to the fact that the mains transformer will be working even closer to saturation (ie will be running hotter), and the lack of HT fuse,may explain why I see so many Blue Junior with dead mains transformers.

The Blues Deville also suffers as the 6L6s are run further over spec on the screens (520 VDC) and I often see the plate load resistors in the phase splitter open circuit, again I think due to over voltage; the resistors are only rated for 350 VDC.

[dave_mc]

^ aren't several of the modern fender amps known to be biased pretty hot? I think the blues junior is as well as the ones you mentioned, maybe the pro junior too? Maybe that's why they have the 240V tap :lol:

[jpfamps]

^ aren't several of the modern fender amps known to be biased pretty hot? I think the blues junior is as well as the ones you mentioned, maybe the pro junior too? Maybe that's why they have the 240V tap :lol:

I think they have the 240V tap so they can make the mains transformer smaller. My guess is that when you are buying in the quantities Fender do the extra tap on the mains transformer is worth adding for the saving on the size of the core.

Regardless, Blues Juniors run hot even at the correct voltage, so running them over voltage is asking for trouble.

[Frank]

Im ne of the unlucky few that has dodgy mains.

My average is 250v but sometimes gets up to around 260v.

I've complained about this and they said there's nothing they can do about it due to the power requirements in the city centre.

Let's just consider that statement for a moment. They're a power company and they can't do anything about the mains voltage to your property which is way above the specified maximum. There's nothing they can do about it.

So when your telly explodes, there's no way you can claim compensation from them is there? Worth a try.

[Toe-Knee]

Im ne of the unlucky few that has dodgy mains.

My average is 250v but sometimes gets up to around 260v.

I've complained about this and they said there's nothing they can do about it due to the power requirements in the city centre.

Let's just consider that statement for a moment. They're a power company and they can't do anything about the mains voltage to your property which is way above the specified maximum. There's nothing they can do about it.

So when your telly explodes, there's no way you can claim compensation from them is there? Worth a try.

This is exactly what I've thought. I've looked into and i can claim. I have also written in with a formal complaint after numerous unhelpful calls. Still waiting to hear back.

[jpfamps]

I was under the impression that maintaining the mains within the standardized limits was a legal requirement, although I could be wholely mistaken in this assumption.

[Toe-Knee]

I was under the impression that maintaining the mains within the standardized limits was a legal requirement, although I could be wholely mistaken in this assumption.

I've recently read this. I need to also check if the neighbours are also high which I imagine they are especially with it being in a block of 32 flats.

[tekbow]

Im ne of the unlucky few that has dodgy mains.

My average is 250v but sometimes gets up to around 260v.

I've complained about this and they said there's nothing they can do about it due to the power requirements in the city centre.

Let's just consider that statement for a moment. They're a power company and they can't do anything about the mains voltage to your property which is way above the specified maximum. There's nothing they can do about it.

So when your telly explodes, there's no way you can claim compensation from them is there? Worth a try.

This is exactly what I've thought. I've looked into and i can claim. I have also written in with a formal complaint after numerous unhelpful calls. Still waiting to hear back.

I love this stuff, more specifically fighting companies who's company policy tells them that they shouldn't give a toss when the law says different. Always great to remind these people that their company policies are the companies guidelines for screwing customers out of the correct service and/or getting their money back as opposed to what is reflected in the law. They rely on the the general public being ignorant of this fact

National Grid in the uk are the ones to speak to. If the voltage supplied to you're building is outside the governments guidelines (i.e. what we should have +/- the tolerences) then you can report the company. I would mention your supplier also said it wasn't their problem. Citizens advice bureau are good with stuff like this too. In my experience it's staffed by people who love sticking it to companies who don't play the game, and finally of course, HSE at the local council. If they're half as anal as the offshore HSE advisors, they'll take great pleasure in getting something done about it

[Toe-Knee]

Im ne of the unlucky few that has dodgy mains.

My average is 250v but sometimes gets up to around 260v.

I've complained about this and they said there's nothing they can do about it due to the power requirements in the city centre.

Let's just consider that statement for a moment. They're a power company and they can't do anything about the mains voltage to your property which is way above the specified maximum. There's nothing they can do about it.

So when your telly explodes, there's no way you can claim compensation from them is there? Worth a try.

This is exactly what I've thought. I've looked into and i can claim. I have also written in with a formal complaint after numerous unhelpful calls. Still waiting to hear back.

I love this stuff, more specifically fighting companies who's company policy tells them that they shouldn't give a toss when the law says different. Always great to remind these people that their company policies are the companies guidelines for screwing customers out of the correct service and/or getting their money back as opposed to what is reflected in the law. They rely on the the general public being ignorant of this fact

National Grid in the uk are the ones to speak to. If the voltage supplied to you're building is outside the governments guidelines (i.e. what we should have +/- the tolerences) then you can report the company. I would mention your supplier also said it wasn't their problem. Citizens advice bureau are good with stuff like this too. In my experience it's staffed by people who love sticking it to companies who don't play the game, and finally of course, HSE at the local council. If they're half as anal as the offshore HSE advisors, they'll take great pleasure in getting something done about it

Thanks for the info. If I don't get a suitable response and solution from the letter I sent off i'll be sure to chase all of this up.

[tekbow]

Pleasure  :D Stick it the to the man!

My most satisfying victory was with a courier service when i sent my stuff back from uni after i finished. 4 boxes came back destroyed, 1500 quids worth of books, computers etc. They'd basically left them out in the rain and someone obviously missed the pallet they were loaded on with the forklift and attempted to drive it thru the box with my computer instead.

4 months i fought that one. got my 1500 quid back, they even sent a guy to take photos because they thought my pics made it look worse than it was. he left without taking anything muttering "the pictures are representative.." that was TNT. Then i went after the agent i booked it with for the £150 they charged. Some Snot nosed legal department cow who couldn't get a job as a real lawyer tried to take tell me the had taken out some order that limits the amount of compensation they had to pay out as TNT had already reimbursed me in full. The order she was talking about is usually applied to divorce proceedings. Took them to small claims court. My argument was that i payed for a service they failed to provide and i was seeking a refund on the fee i paid to them. the judge/arbitrator/whoever it is presides over small claims court laughed them out and got me my money back. I think he was enjoying himself. This is a good example of how large companies think people are stupid and aren't capable of looking something up.

[dave_mc]

I think they have the 240V tap so they can make the mains transformer smaller. My guess is that when you are buying in the quantities Fender do the extra tap on the mains transformer is worth adding for the saving on the size of the core.

Regardless, Blues Juniors run hot even at the correct voltage, so running them over voltage is asking for trouble.

yeah that's what i meant (your last sentence). Something that's not running so hot at "normal" voltage might be safer even if the voltage were slightly higher.

though what you're saying about the transformer probably has a large bearing on their decision, too. :)