Further to Robbie Rhodes' comments on the Sola and similar voltage
regulators, they are very frequency sensitive because they are resonant
circuits.  They work fine when the mains frequency is stable but only
make matters worse when the frequency varies.  I tell you this from
personal experience.  If you are going to use one you would of course
make sure the wattage rating is sufficient for the load, then make sure
the frequency of the regulator is right (Jakarta, for example, probably
has 50 Herz mains), then verify that the mains frequency is stable.

It's been over 30 years since I looked at one of those regulators,
but I would guess the tolerance is about +/- 1 Herz.  There used to be
a mechanical voltage regulator that was not frequency-sensitive.  It
consisted of an auto-transformer adjusted by some kind of a voltage-
sensing circuit.

Lightning is a big problem in this area (central Florida).  I have a heavy
duty spike protector at the mains entrance and then the usual small ones
for each piece of electronic equipment.  Two very close lightning hits
have not given any problems.  (I also cross my fingers).  The heavy duty
outside protector protects the inside protectors.

Fritz Gellerman

 [ The ordinary transformer doesn't offer the protection that the resonant
 [ line conditioner provides.  The two types are often installed together,
 [ however.  The line conditioner is usually rated for +/- 5% change in
 [ mains frequency, or +/- 3 Hz at 60 Hz.  -- Robbie