Hi all,

Well it's been about three months of on and off progress (and setbacks), but I finally seem to have a working, dependable HX machine. Awesome.

I purchased a 2004 Nuova Simonelli Oscar machine for a bit under $200 in partially working condition. The seller said it trips the breaker every now and then, but recently it had been doing so more frequently. Having rebuilt a HX machine before, I felt like I could handle such a project. The only difference is that I don't have access to my father's machine shop as I now live several thousand miles away. Regardless, I managed.

Here's a before shot:


I did a complete tear-down, cleaning and descale, sealed the frame (or what was left of it), and replaced a couple of worn out bits here and there. I also added some extra goodies like a bottomless PF and the new style small-hole steam tip (NOTE: NS decided to use 1/8" BSPP here instead of M10 thread! I learned the hard way). An over-pressure valve mod kit is still sitting in the parts box; I want to get a feel for how the shots pull before installing it to compare the results.

Perhaps the most tedious part of the project was replacing a burned out chip inside the controller box. I learned how to solder surface mount components at a communal "maker space" in the city. That alone saved me close to $150, which would have put the cost of parts over the initial investment. Not my cup of tea.

I had a lot of fun working on this machine and would encourage any mechanically inclined folks with some spare time to take on such a project. It's rewarding, and not just in terms of great espresso!



You can view the entire photo set here: Nuova Simonelli Oscar rebuild project

Thanks to all who have come before me. I couldn't have done it without your help. I hope this ends up being useful to somebody in the future.

Cheers!

Great photos - I can particularly relate to the saga of removing the heating element. My challenge was removing the diffuser from the group - I went through three successive attempts to fabricate a pin-insert wrench before finally succeeding with one that had a handle a half meter long!

Can you tell us more about the rust removal by electrolysis? Can scale be similarly removed?

Enjoy the coffee - I think it really does taste better when you make it yourself!

Oh, that was a real headache. I was ready to give up on the boiler after banging, torquing and heating when suddenly it un-froze. That was a happy moment!

If you do a YouTube search for "electrolytic rust removal", you can watch a couple of videos with thorough explanations of how to set it up. Basically, rust is an oxidation-reduction reaction (a.k.a. redox) where iron gives up electrons. When you run a current through iron or steel parts using sodium carbonate solution as an electrolyte, the reaction happens in the opposite direction. After brushing the rust buildup off the part, the remaining rust actually reverts back to iron on the part while your sacrificial anode gives off its electrons. It's not perfect, but it is a considerable improvement over mechanical rust removal alone.

Just recorded a small video making a cappuccino with the smaller 4-hole tip. Still getting used to it, as you can tell... Forgot to mention that I installed thermosyphon restrictors in the grouphead, which reduces the length of the cooling flush to almost nothing. Big thanks go to Márcio's restoration thread from a couple years back for the idea!