Sunday, December 18, 2016

Starbucks Barista Espresso Maker – Disassembling procedure – How to remove the heater and pump


Remove the six Phillips screws securing the chrome rear panel to the Barista.
Once the chrome panel is gone, you get a pretty comprehensive look at what makes the Barista boil. Major components include:
A reciprocating pump.
A pressure release valve
A boiler (with an internal heating coil).
A steam valve which, as you guessed it, allows steam into the steam wand for making frothy milk.

A bird's nest of wiring supplying power to everything.
Remove all the Phillips screws holding the AC power cord and distribution block to the frame.
The pump is responsible for drawing water up from the reservoir to keep the boiler supplied with water to boil.
First, remove the two clear plastic hoses from the barb fittings on either end of the pump.
When removing hoses from barb fittings, it is helpful to use a probe  to separate the hose from the metal fitting before pulling it off.
One hose is responsible for drawing water up from the reservoir and the other returns excess water if the boiler is filled to capacity and reaches the preset pressure of the pressure release valve.
Use a wrench to remove the boiler hose from the pressure release valve.
Remove the two slotted screws securing the pump brackets to the frame of the Barista.
The simple angled rubber pump brackets are designed to absorb vibration from the reciprocating pump.
Disconnect the two female AC power spade connectors from the pump and slip the thermal fuse out from its holder on the body of the pump.
The thermal fuse is a normally closed protective switch that opens the circuit once the pump has reached a critical temperature, thus shutting it down before the coil melts.
Remove the two Phillips screws from the pump manifold and lift it off the end of the pump, minding the two locking tabs near its base.
The pump used in the Barista utilizes the electromechanical properties of a solenoid to pump water up from the reservoir.
An iron core placed in the center of a cylindrical coil of wire is reciprocated back and forth through the coil when AC voltage is applied to it. Springs on either end of the core absorb its kinetic energy.
The core is attached to a plunger (outlined in green) that fits tightly into a cylinder on the pump manifold which creates the pumping action when the core moves back and forth.
The pressure difference between the inside of the cylinder and the water tank causes water to be drawn up from the reservoir into the pump, whenever the steam valve is opened, to assure the boiler is supplied with water.
Disconnect the spade connectors from the digital switch near the steam valve knob.
When you open the steam valve knob (to steam your milk), a cam attached to its shaft presses the digital switch, closing the circuit. This either starts the pump, gives power to the heater, or both, to produce steam.
Disconnect the two large connector blocks.
Several power leads connect to the three switches on the front face of the Barista for different operating modes. They include:
Device Power (On/Off)
Brew
Steam
Use an 8 mm bit driver to remove the four hex bolts from around the perimeter of the boiler (only two are shown).
Remove the 2 mm hex set screw from the steam valve knob and pull it away from the piping to remove it from the Barista.
At this point, the boiler is free from the Barista and can be removed
Opening the heart of the Barista: the boiler.
Remove the four hex bolts securing the brew head to the boiler assembly.
Lift the brew head off the boiler.
Remove the single Phillips screw securing the brew screen and gasket to the boiler housing.
The brew screen helps to evenly disperse water across the grounds in the basket.
Use a large standard screwdriver to remove the one-way valve spring retainer from the bottom of the boiler.

The one-way valve spring is tuned to only allow the valve to open when the pump is running.
This prevents the brew head from dripping while warming up.
Use a flat blade screwdriver to separate the two halves of the boiler. Inside the boiler, you can see the main components:
Boiler housing (to contain water and steam).
Heater coil.
Dual thermal sensors, presumably one to maintain steam temperature and one for max temperature shut down.
The bottom portion of the boiler housing has a rigid hose reaching toward the top of the boiler to draw water from the top to keep the heater coil immersed in water.
There are also two Klixon thermal sensors. The numbers stamped around their bases are:
1NT01L-0036 L95-10 9910 M 10/250~T200
1NT01L-0499 L127-15 9912 M 10/250~T200