Nuova Simonelli Oscar II OPV hack 

Bingo!!! Nice work Travis!

You are right descaling them is quite involved. I dont have the machine so a video is out. If I recall the process: there is a hex plug located low on the boiler. Drain boiler. Then refill the boiler manually with a descaling solution ( the same qty you drained out). The replace the plug. heat up machine and then let it sit for a few hours. Then turn off machine. once cooled it will be safe the remove plug and drain out descaler. The rinse out the boiler (pour water in, swill around, empty). Finally, refill boiler with fresh "soft" water. Good luck.

It is a pretty generic pressure gauge that has the same tread as almost all 58mm portafilters.

@@espressorestomelbourne1735 Thank you!

There is adjustment yes, you can wind it in or out. Additionally you could remove a coil from the spring to get a great range of pressures

I cant see why not. Commercial machines have OPVs

Actually no, I think it might have been fitted locally by importer and then sold as a pro model or something

www.jetblackespresso.com.au/shop/p/isomac-expansion-valve

Sorry, I don't know Indonesian. If your machine is overheating it is probably that the pressure stat has failed and you need a new one.