Moving to Europe, how to care for my GM40 there?

Hey everyone,

I'm moving to Europe and I'd like to bring my GM 40. What should I do? Buy a step-down transformer even though that doesn't convert the frequency? Or, does the GM40 have built-in capabilities to deal with US or Europe power supplies? Otherwise, can I have installed a new transformer or modify the one currently in it? Any advice would be appreciated.

Thanks,
lancaster2124

Hi Lancaster.  I think that from the outset I would want to have H&K's own advice on this one.  I've asked them on their Facebook page but other questions have not been answered in any quick time recently.  Whereabouts in Europe are you moving to?  It may help to know that.

The problem looks a simple one to fix at first glance.  To switch between 230V and 240V seems to be just changing the tap on the mains transformer primary.  The GM36 schematics show that and I would guess the GM40D is the same.  Looking at it, it seems that the mains Tx has a single primary coil which takes 240V 'OR' 120V across its ends.  There is then an additional tap which accepts 230V 'OR' 100V.  Now that suggests that the Tx is a different model for each pair, 230V/240V and 100V/120V.  That is to accommodate for the US 110V market, both the UK and EU markets should use the same Tx.

I would try getting a tech to explore the possibility of swapping over the connection inside.  I have no idea what form they would take.  It could be a simple push on maybe "spade" connector swap or it may take more work soldering.  The schematic shows that the wiring between mains switch, fuse and transformer primary is direct and off the PCB so it should be simple.  However, it does give no suggestion of spade connectors which it does show for every other connection to the boards.

I'll keep you up to date with any of H&K's replies or anything else I can dredge up about this.

Hey there, thanks for the reply.

I would also probably like HK's advice on this one. I guess my original post may have been mis-worded becuase I already did move to Europe (France, specifically) and have the amp with me. So my options are kindof limited (as in I can't sell the amp in the US and then buy an EU one). I think you're probably right that it seems it should be able to be switched over - I'll try to get in touch with HK techs and see if they can't hook me up with a tech who can make the necessary adjustments. I really hope it's not too costly, though. I know this kind of thing can be really expensive.

Ah, now that sounds like you have moved from the US to France.  That's not so easy to deal with.  If that's the case then sorry for assuming you were a Brit, (and my deepest commiserations and sympathy for you not being one ).

Here is a pic of the GM36 mains section.  As I've said before, the GM40D is in the same family and will no doubt share many of the same design considerations.  If it 'aint broke don't fix it!  The mains section needed no changes to how it had been and is probably very similar if not identical.  You can see that all of the connections are made with those 1/2" 6.35mm "spade" connectors.  Uk -> EU conversion is most likely just swapping one tap for the other.  If you have an American amp then this is not possible as I said.

EDIT:  Should have added that all of the connections up to the secondary windings are made with no PCB involvement.  From the mains socket which also carries the fuse, to the mains switch, to the mains transformer primary upper end or tap, and from the lower end to neutral is all direct wiring.

Hey, yeah, I’ve got an American amp that would need conversion to EU somehow. I guess the only real route in that case would be get in touch with HK officially and see what they say to do. In the time I may just get a transformer so I can start jamming again.

The part number for the 230V/240V transformer is 9580257.  I have found a reference to a European parts supplier showing it at 108.22 Euros but not in stock at the moment.  Mains Tx Supplier  If you want to get on to H&K Support you are better using Facebook than email.  They have a much better record of responding more quickly to FB as they say it is easier to follow and to respond to when out on the road.

I've had a response from H&K on your issue Lancaster. It won't help you but it does clear something else up for us. I originally asked them about rewiring the mains section to accommodate EU voltage from UK as that was what I thought you were needing. I hadn't realised at that point that you were in the US. (I often am working very late at night and I do get a bit dozy, it's my error not theirs.) They report it isn't really necessary as they have a lot of guys using their gear on the continent after just swapping the plug with no problems.

Remember, the EU and UK mains voltage standards were fiddled to bring them more into line. That included a loosening of the tolerances so they overlapped. The H&K kit seems to have been designed to cope with that wider range of supply voltage. If you are moving between the UK and EU there is no need to do anything except power through a mains socket convertor. For myself, if I was living on the continent I would definitely see if I could change that tap over on the Tx anyway. It's there for that job, (as long as it actually still IS there as the older service manual shows). Now that doesn't help you but at least we have H&K talking to us about this. I'm sure they will be able to give us a little more info now I have corrected the original query.

I've had a quick look at stepdown transformers too. I am really surprised to find that good quality units are only about £40 on Amazon, and I'd bet they will be cheaper in the US. If you look at the GM40D spec you will see it has a max power consumption of 200W, (the power going into the unit is what we need not what we think we can get out of it). I would go for considerable overkill on this one. A smaller unit will show less solidity in its output voltage and may even be put under stress heatwise. A 500W unit with US and UK sockets and which works both ways is neat and tidy and just under that £40 mark. You may even find it helpful with some of your other US gear too. That will be less than a replacement for the Tx in the amp itself, I would guess a LOT less. How are prices over the water in the US?

Hey! Thanks again for getting back.

While it would be nice to not have to haul a stepdown transformer everywhere I play, I guess that's a sacrifice I'll have to make (at least until I can bring it back to the US on a trip, sell it there, and buy a new one here!). I'm glad to hear that the solution should be relatively simple in any case. Thankfully the prices for stepdown converters that are 500w like you recommended _and_ go both ways are about the same as what you've seen.

I really appreciate all your advice. You've been a great help.

Glad to have been a little help. If H&K give us any more useful info I'll be sure to post it here so keep an eye on things just in case it is helpful. Good luck with the move to France. I love the country and I genuinely envy you, all except that French "bicka bocka ding dong" style pop music they seem to love!

I've had a reply back from H&K. Their advice is to not worry about what is inside the amp as it is designed as a unit to work for a specific location. They recommend using a step-down transformer to feed it as it is. That will leave the whole unit intact as designed. In a way that is a good option as it is cheaper and may even give you the ability to use other US gear you have in France as well.

Hope that is ok to round off your issue. Bonne chance et reste en contact Lancastre. Good luck with playing Plastic Bertrand and Johnny Hallyday.