How to Identify and Rewire a 1994 French Tennis Stringing Machine Transformer for 220V?

Hope somebody can help me out with this.  Attached is a picture of a transformer from an electronic tennis stringing machine.  I am in no means a engineer or an electrician.  I've come to these boards becuase nobody in the tennis world who are familiar with this machine was able to help me.  Now here is the problem.  This machine was used in the US where the voltage was 120v.  The machine has recently been reloacated to Hong Kong where the standard line voltage is 220v.  Can anybody tell just by looking at it that this is a multi voltage transformer?  Also if it is how do I rewire it to accept 220v?  I have been told from other owners of the same machine that it should be multi voltage but nobody was sure about the wiring.  The machine was manufacured in France around 1994.  Again I hope somebody can help me out with that.  Thanks

Well from the looks of it, it has two secondary winding. Technically, what you need is a step-down. If you can notice, the e1 and e2 are soldered together. the same goes with s1 and s2. That is the reason you get 220-240V. So if you unsolder them somehow, that would return it to 110 -120V.

At the moment the pictures reflect the transformer wired for 110v-120v already. So I'm a bit confused. Did you mean If I unsolder the jumpers I would be getting 220v-240v? Someone else suggested I unsolder e1 and e2, as well as s1 and s2. Then keep the brown wire at e1, solder e2 and s1 together, and keep the blue wire at s2. Any thoughts?

The present configuration will have the two primary winding's paralleled for 115V AC.
You need to remove the existing links and the blue neutral wire(cut them, heating may damage the plastic bobbin if overheated)and reconfigure it to put the two winding's in series for 230V AC.
Verify that the windings are identical with an inductance meter (or ohm meter if thats all you have). If they are near identical, put the blue wire on S1, and a jumper between E2 and S2. Again, take care to avoid overheating the lugs, or the bobbin may melt down. Put heatshrink over the neutral lead and lug.
The trick is to get the phasing correct, the end of the first primary winding goes to the start of the second primary winding, phase and neutral to the other ends.
This is my take on the evidence presented, don't hold me responsible if it doesn't work,
cheers,
Richard

Thanks Richard for commenting. Before I read your comment I took the links off e1 & e2 as well as s1 & s2, while leaving the brown wire at e1 and blue wire at s2. When I plugged the machine into a 220v line nothing happened. Machine would not turn on. I got a bit scared and rewired everything back to the way they were just like the pictures. Plugged it back into a 120v line and everything thing is working the way it should. You mentioned testing with a inductance meter? How would I go about doing this? I have a multimeter, but if there is a sure way to test all of this before executing what you suggested, I am all for going out and buying an inductance meter. The last thing I want to do is damage the machine. So if there is a way to test all of this first, that would be the ideal way to go about it in my logic. Please let me know what you think? Again thank you for your help.

Many multi meters have an inductance range on them. However, both winding's have the same gauge wire, so they should have about the same resistance. Switching the two winding's from parallel to series should double the resistance between the phase and neutral leads. The advantage an inductance meter has is that in measuring the inductance, you can tell if the phasing is correct. If you get the phasing wrong, the inductance reading will drop to a low value, otherwise, it should go up by a factor of around four between the phase and neutral leads. Incorrect phasing will result in next to nothing in the way of secondary voltages.
If the thing is wired the way I think it is, then cutting the two links would leave the winding set for 115V, putting 230V on it would double the output voltages.
As an example on a real low power transformer with two primary windings, your transformer is larger, so expect differences, but the same principle applies.
winding 1 40 Ohms
winding 2 49 Ohms.
Set for 115V, parallel windings, correct phasing.
Total resistance 23 Ohms, Inductance 620mH.
Set for 230V, series windings, correct phasing.
Total resistance 91 Ohms, Inductance 2.94Henry.
If the windings are out of phase, then the series resitance is 88 Ohms, the inductance 10mH.
Hence you can see the advantage of an inductance reading.
Obviously you can apply a voltage and get voltage readings, but as you have seen, this is fraught.
Cheers,
Richard

OK let me check with a multimeter to see if the ohms are consistent. Also if Im hearing you correctly, with all that said, setting this up in a series would double the resistance which is what I want since I have double the voltage. And to set this up in a series I would cut the links between e1 & e2 as well as s1 & s2 while keeping the brown wire on e1 and blue wire on s2, then linking e2 and s1. This will provide me to accept 220v to the primaries. Does this sound right?



e1 e2---------s1 s2

As I said, I believe the link should go between S2 and E2, the blue wire on S1.
That puts the two primary windings in series, with the correct phasing. An ohmmeter will show double the resistance between phase and neutral, but it won't tell you that the phasing is correct. The start and finish of the winding's can be deduced from the way the primaries are linked for 115V, both have to have the same phasing, so we can arbitrarily say that E1/E2 are the start of each winding, and S1/S2 are the ends.
In series, you have to have start/finish to start/finish,
does that make sense,
cheers,
Richard

Hi, my mistake. Just realized what E and S stand for, I have been somwhat slow on the uptake.
Start 1 and End 1, Start 2 and End 2, silly me.
So yes, your linking is correct, cut the existing links and put a new link between E2 and S1.
Some times you just can't see the woods for the trees, I would have checked it with an ohmeter to verify it, but not having access to the transformer, it just wasn't going to happen. I should have realised when you said earlier that nothing happened when you removed the links, there would have been an open circuit in the windigs!
cheers,
Richard