I'm a bit confused reading this thread, Shawn are you saying that isolation transformers are not a good idea in general or just in this case
whether it's required or not is determined by the type of power supply in the monitor. while it does provide some safety to the service tech in some specific circumstances... it's not particularly required for safety or anything.
TL;DR :
if the monitor has a regulated power supply, then YES you require the isolation transformer.
if the monitor has an SMPS power supply, then NO it does not require an isolation transformer.
I think, it runs from a 128vac Isolation transformer and 240vac for the degaussing coil
occasionally overseas cabinets made in japan (where the voltage is 110 volts) will use a standard 110 volt monitor with a stepdown transformer (240v input to 110v output) where a cabinet is sold into a country where the voltage is 240v. this standardizes parts. in cases such as these, you would have to retain the step down transformer if the monitor is regulated, (since the stepdown transformer also acts as isolation from the mains...) but could be omitted it if the monitor has been replaced and contains an SMPS powered monitor...since the SMPS can deal with voltages typically from 90 all the way up to to 250 volts.
TL;DR:
if the monitor has a regulated power supply, then YES you require the stepdown transformer.
if the monitor has an SMPS power supply, then NO it does not require the stepdown transformer.
you can retain the isolation transformer even with an SMPS powered monitor. just be aware that the isolation transformer has a limited output and may cause issue if the monitor connected to it has been changed in the past to a different unit and is close to or exceeds the safe output current carrying capability of the transformer. (transformer would run hot and possibly fail)
and yes, the hantarex 9000 requires isolation.