So I have this crappy Starbucks Sirena that is finally giving up the ghost after about two years of solid usage.
I want to retire this machine to my office, in a fancy new chassis (I have something crazy in mind ;) after refurbishing it, PID-ing it (Arduino), replacing a few parts (steam wand is allegedly Gaggia compatible?). At home, I'll upgrade to something else.
This isn't a quixotic "make the Sirena a god shot pourer" machine project, but rather something to learn more about the inner workings and hone some skills. So I'll probably have more posts :)
My first order of business is just understanding how this thing works, and targeting parts for refurbishment or replacement. I noticed two symptoms before it died.
1) boiler noise was non-existent. You used to actually hear the sound of boiling from inside it. No longer. 2) steam pressure reduced to just about nil.
This machine was regularly descaled using either specific espresso descaler or a citric acid solution.
I've attached a diagram I made of the water flow through this unit. So, three questions:
1) there are two outlets from the water reservoir leading to the pump. One of which passes through a "turbine" (as the parts diagram calls it). How does this work exactly? Why two pipes?
2) should I start by disassembling the boiler, thermoblock, and wand valve, and soaking them in something more serious like CLR? I guess then I may as well replace all the hoses.
3) if anyone can recommend books on espresso machine inner workings, that would be great. Google turned up just about nothing! I have learned the small amount I do know from this forum, for the most part. I'm unclear on some basic stuff like how pressure is built-up and kept contained in the boiler, I assume there are a few one way valves here and there …
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