Looking for some help from the STAX experts. (Posted this in the High End Stax thread but got no response.)

I am assuming that if I move the Brown->Green jumper to Blue->Purple and move the white (top left) wire from Brown to Purple, then I will have correctly configured my SRM-007tA for 117V.



Is this correct? Thanks!

This is posted without any guaranty but should work. There are two 0-100-120v windings on the transformer so you want to change from a parallel wired 0-100 over to parallel wired 120v configuration.

100v should be Gray and White connected together (they are the 0v points of the windings) and then Brown, Green and the other white wire (which is connected to the power socket) connected together.

117v should be White and Gray connected together (0v point) and then Blue, Purple and the other white wire connected together.

240v should be Blue and the other white wire connected together and then Purple and Gray connected together.

That means you have to move the jumpers as well as the white wire (not the one connected to the fuse!!!!!) over to the spot above the purple wire. You were dead on.

One thing to note is that Stax does sometimes cut the 120 windings on the transformer making this change almost impossible. Check and measure the primary windings before proceeding.

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Thanks Spritzer!

Luckily, the primary wires were not cut so I should be to go. Your verification is most appreciated!

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Lucky indeed. It was a pain to solder the windings on my 717...

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Hi Spritzer,

Is 007tA configuration the same as the SRM-717 , in other words, can I do the same to change the 100v SRM-717 to 230v?

Anyway to implement a multi-voltage switch like some versions of the SRM-717?

It is similar but there is no way to tell if your unit is that way without looking inside. Stax change this up regularly so just take off the top cover and have a look behind the transformer. I would also remove the PCB cover to see if the windings are still in place (they are the bare wires that go from the terminals and into the transformer).

You could add a switch but it isn't simple. The unit that Stax used isn't a switch but a plug that you can remove and rotate to get the correct setup of the primaries. A normal 117v/230v switch will not work.

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spritzer, thanks for the reply!

I'm not very proficient in electronics and all these electrical thingy, so pls bear with me.

Are the circuit boards of the stax running at 230V, in other words, is the output from the transformer to circuit 230V?

The other concern is whether regular/normal soldering is suffice or do I need some kind of special solder for Stax? Probably passed the unit to a friend to do it for me...

The output from the transformer is more like 300v+ (plus a few other voltages for +/-15VDC and the filaments) but you don't have to worry about that as you never come near it. The output of the transformer is called a secondary (and there can be many) but it's the primaries (inputs) which you have to rearrange. There are 6 input wires which need to be put in the right order and you could even have to add some wires as well as Stax left them out on the 100v units. Just open up the unit, take a picture and we can take it from there.

If you have to do any soldering then any normal solder for electronics will be fine. You may also have to remover some solder as well.

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Thanks spritzer!

just wondering if anyone happened to have any pictures your 717 that is configured to 220/230v. At least I can show the soldering guy how exactly he should do it. thanks!

Nope sorry. I was far too worried at the time about my transformer surgery to take any pictures.

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Ok, here are some pictures of the SRM-717, is this sufficient? not sure which screws to take out....

That's the fuse board and here is the code to change it:

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So you should have metal jumpers in spots 1,3 and 6 so just pull them out of the clips and move them accordingly. Make sure to get a good contact as there is live AC voltage floating through. It's a bit of a pain to get to the board but nothing too complicated.

What you need to check is if Stax cut the transformer windings before you change the voltage settings. To do so you have to take off the green PCB that's on top of the transformer and follow the wires as they enter the transformer. The wires that come off the fuse board are soldered to metal pins which also have enamel coated wires soldered to them. Those wires are the windings and should all go inside the transformer and out of sight. The PCB is just fixed with some double sided tape to just pull on it.

Thanks spritzer, you're the man!

So if Stax cut the transformer windings, what's the next thing I should do?

In worst case scenario that the Stax can't be modify... worst worst case, what would be a good transformer to recommend for it?

The transformer is custom unit so it would be hard to replace with some off the shelf unit and a custom one would hardly be cost effective.

If the windings are cut then you could attempt to solder them. I did so on my current amp and it works great on 240v and has done so for about 6 months now. It's possible to do so if you can see and reach a bit of the winding with the soldering iron. Attach lead wires to the terminals for the windings and with everything pre-tinned I pressed the winding and the lead wire together with the hot soldering iron and got a good connection. I did break bit off the plastic surround to do this but it is mechanically solid and there is no extra resistance due to the joint.

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Sound like brain surgery to me...

As for the transformer, I'm looking at those Japanese external ones... was told that I can minimise the RF it generates by putting an aluminium encasing around the transformer...

Having said that, I'm going to wait for my friend , who's out of town now, to help me with the major op... I really hope the windings are not cut, else it's spending another 100 bucks to get another transformer just for it.