This is a quick look at the internals of the Vibiemme Domobar espresso machine, the one with the single boiler which you heat up to about 90deC to make your espresso, and then switch it to steam and allow it to further heat up to 145decC for you to foam your milk.
I explain this, because there is also a version with a larger boiler and a heat-exchanger which allows the simultaneous brewing of coffee and steaming of milk. I have some internal photos of this machine also and will post them shortly.
Okay, covers off.
Beneath the top cover is the water tank. This sits on a sprung platform, and unless there is sufficient water in the tank it will not press down sufficiently on the micro-switch below the sprung platform. The prevents the element from heating up and causes much frustration.
Here is the sprung platform removed and upturned to show the screw which presses on the micro-switch lever arm.
The micro-switch sits under the water tank and sprung platform. Unfortunately, the lever arm can become bent, and this can make the machine think that the water tank is prematurely empty.
Here is a first view of the boiler, to help you get your bearings.
The group head is heated by thermo-syphonic action and has two copper tubes forming a circuit via the boiler. With the boiler up to temperature, the heated water will flow through the group head without the need for any pump, and so keep the group at the perfect temperature for brewing. The two pipes to the group connect to the boiler approximately half way down on either side.
The steam valve is fed from the centre tapping at the top of boiler, and is connected to the separate steam arm. Within the boiler is a thermostat pocket, which accepts the vial from the capillary thermostat situated at the top right. This sets the coffee brewing temperature and has an adjustment accessible from above..
There is also a bimetallic steam thermostat screwed to the top of the boiler, which opens at about 145degC.
The Vibiemme uses an Ulka EP5 water pump, which is able to provide up to 15 bar of pressure. This is reduced with an Over Pressure Valve (OPV) to around 11bar, which bleeds water back to the water tank to reduce the system pressure. It is recommended to reduce the brewing pressure to approximately 9 to 10 bar, but to do this it may be necessary to disassemble the OPV and cut a turn off the spring.
We hold stock of spare parts for the Vibiemme Domobar, including the element (1800W), brew capillary thermostat, shower screen, group gasket, Ulka EP5 pump, power switches, descaler cartridges, and bottomless portafilter.