Hey guys, it's been a while since I logged onto this webstie.
So, I'm currently attempting to mend my old table lamp. The ballasts in there don't sound good anymore, anyways that's what the main problem is. The fixture came with two 10W 110V ballasts, while the mains in my country (Indonesia) is 220V. I bought a 10W 220V ballast, it doesn't fit in the fixture, so, should I buy two more 10W 110V ballasts? I still can find them somewhere though, but is it safe to do? Wire them in series?

Wire it as two independent 120v lamps, then wire those in series. Still only two 120v ballasts. I can draw a simple diagram if you would like.

Thanks for replying,
Could you draw the diagram, please?
Thank you very much.

Like this:

So do I need two lamps?
Because the fixture only can fit one tube.
Thank you.

Update :
Here you can see the fixture : https://www.lighting-gallery.net/gallery/displayimage.php?pos=-237750

Wait, so the fixture has two ballast but only one lamp? That is very odd. If you know how it was hooked up before it is probably fine to just put it back how it was but with new ballasts.

Alright, thank you so much for helping me!!

You can also use 220V ballast in a suitable external box somewhere on the power cord. My usual advice is as always when in doubt you should use a true RMS multimeter to check tube current you are getting. Asian 10W tubes are 0.22A (if I remember right, please check).

Late here, but anyhow. I guess what they done there is 2x 110V ballasts in series = 220V ballast for same lamp. For short lamps with low arc voltages like 4..6 T5 it comes out fairly close to the proper ballast value

I tried to work out the lamp arc voltage for 10W at 0.22A, i get 57V similar to an 18/20W lamp. Which sorta surprises me. I am not familiar with the 10W T8 but i expected to see lower voltage, higher current there

There areactually two completely incompatible "10W T8" lamp types present (at least in Europe), one is ~30cm mainly far east origin, which runs at 0.22A, so the same ballast as e.g. the 15W T8.
The second is about 45cm (lengths are with at least +/- 5cm tolerance, I do not remember it that well) long, rated at 0.17A, so the same ballast as the PL-S family or the 4..8W T5 tubes.

You can pretty well use two 120V chokes in series (you literally need about double ballast voltage drop with 220V mains vsthe 120V mains), but the problem is,theyneed to be designed for the same mains frequency you have. And there I would suspect a problem - the "120V world" uses to run 60Hz, while the "220V" one 50Hz (with the exception of Japan, which is a separate mess on its own).
So better to check the circuit current while the lamp is running - if it is what it should be, you have a good ballast setup. If the current is higher than the ballasts are rated for, you have a big problem - the ballasts will overheat. Otherwise the lamp isn't that much picky, something between 70..110% of the rated current uses to be OK, obviously the lower current will make the starting to wear the lamp faster.
So in fact you may even get away with a PL-S (some allowing a single PL-S 7W tube) ballast running the 0.22A lamp.