I had some interesting issues running my SOL-20 from "230V 50Hz" in Australia.
A lot of the time in supposed 230V countries the voltage can be over 240, even as high as 250V rms because of solar inputs to the grid. If you buy a stepdown transformer , if you have to use the "110v" because the primary of the power transformer in your computer has only the 110V winding, then you can end up feeding it with 120V or more.
In these old linear supplies, the dissipation of the many 5V regulators on the S-100 pcb's is increased if you feed them with too high a voltage. The absolute minimum for a 7805 regulator is 7.5V input. In my sol, just with the usual 2:1 ratio step-down mains transformer the voltage presented to the regulators was around 10 or 11V when ideally it would be 8v.
I found with about 98 to 100V rms line voltage, the Sol's DC supplies were producing about 8 to 8.5V to drive the 5V regulators. This reduced the heat dissipation on all the S-100 boards significantly. (my sol has the power transformer that was designed for brown out conditions and there is a mod to lower its output voltage)
To get the 100V rms I simply use the step down transformer, like this (make sure to get one where the earth is carried through to the computer chassis):
https://www.jaycar.com.au/120w-240-120v-isolated-stepdown-transformer/p/MF1080
And to reduce the voltage to this transformer with a variac:
https://www.jaycar.com.au/search?text=variac&CSRFToken=20bec32b-62e1-42f6-bdb0-b20a6021696c
Probably a suitable voltage for most of these old computer linear supplies is in the order of 105V to 110V rms to help keep the heat dissipation on the low side as it can add up with a number of boards and regulators. 115 to 125V is on the high side, especially on 50Hz. Applying a lower line voltage also helps with the frequency issue, one thing with American 60 Hz transformers, some (not all) have their cores pushed harder towards saturation on 50Hz magnetization cycle and they have high core magnetization currents and tend to overheat on 50 Hz. Running a lower input voltage helps this issue too. They can also have higher radiated magnetic fields, which can interfere with your CRT monitor, if it is nearby. If the applied line voltage is too low, ripple will start to appear in the regulated voltages, this is immediately obvious in the video on the CRT output as hum bars appear in the video image.
Al least if you have the Variac you can tailor it to suit your locality. And of course you could just use the variac on its own to dial the voltage back to around 105V, but I still use the stepdown transformer too as there is less chance of an over-voltage accident if the variac is dialed upwards by mistake.
(just as an interesting technical point, the peak flux density experienced by the core of the power transformer is proportional to the applied voltage an inversely proportional to the frequency. So if the frequency gets altered by 50/60 this can be countered by dropping the voltage to 83% of what it was, in practice this is quite a lot, lowering a 120V supply to about 100V. So inevitably, American power transformers end up running higher peak flux densities on 50Hz systems).