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Yamaha TX-7 Power board conversion

Posted: Wed Dec 14, 2016 6:43 am
by Thohi
Ahoy fellow synth geeks!

I recently moved from Europe to the US (what a time for it, eh?) and brought a couple of my babies with me, including my TX-7. Naturally, this runs on 220V, but I'd like to convert it so I won't need my stepper. This was easy with my Roland D-50, but seems less obvious with the TX, so I was wondering if anyone had any experience with this and could give me a few pointers? I wouldn't say I'm a master solderer, but I do know how to user a soldering iron.

Any help / advice much appreciated.

Re: Yamaha TX-7 Power board conversion

Posted: Wed Dec 14, 2016 3:42 pm
by jxalex
Its not good enough, you have to know also how to solder the right detail to right place.

I do not have the service manual handy just now, but...

Just open the case at first, does the transformer is meant to use for several different mains voltage?
there can be on transformer in that case markings on the pins like 0 110 220 240 for each pin. If not, then you have to use stepper transformer.
If the transformer actually has these markings then read on.
If that synth was for europe use then the voltage cable is soldered to 0 and 220 pin. Now thats the most important part. What you need to do in this case is just that you solder that wire on "220" to "110" instead. So...
if before these 2 wires on transformer were on 0 and 220, then the new configuration is that these wires are
on 0 and 110.
And this is it. Also you have to use 2 times stronger fuse in the apparatus (it is NORMAL when going to lower ac mains, becouse it uses the same amount power, but with lower voltage it uses more current). So if the original one was 0.25 then you replace that with 0.5A.

Just this way I had modified several Roland synths (but from US voltage to EU voltage). Behind the case written 110V AC, and seller supplied step-down transformer. But inside the synth was transformer which was for multiple AC mains possibilities and so I soldered to EU voltage with the same recipe like I wrote here. ;) Those synths were JV1080 and JD990.

But this trick is usable ONLY IF the transformer has this kind of markings and pins like it is meant more than for just one mains voltage set! There are transformers which have markings like 0, 110, 220. There are transformers which also have these markings, BUT only 2 of these pins are used. But this you have to check with multimeter (in a ohmmeter range. ANy multimeter with even $5 price range will do!).

The third option, which is little bit more advanced : you replace the transformer inside which has the same output voltages, but usable with 110V AC mains.

Let us know how it went.

Re: Yamaha TX-7 Power board conversion

Posted: Wed Dec 14, 2016 6:48 pm
by minime123
if you dont really know what youre doing, id recommend taking it to a professional or just using an external convertor. some convertors can power lots of items - if you moved a lot of stuff, rather than convert each, perhaps plugging everything into the same converter would be the way to go?

Re: Yamaha TX-7 Power board conversion

Posted: Thu Dec 15, 2016 11:14 am
by jxalex
its not so complicated.

well, I am professional too.

Re: Yamaha TX-7 Power board conversion

Posted: Thu Dec 15, 2016 7:15 pm
by minime123
no, its not so complicated, but messing around with power supplies if you're not really sure about what you're doing can be dangerous, which is why i recommended taking it to a professional if in doubt.