I’m very please to have picked up an Azkoyen Bravo 1-group for only £67.
Listed as spares or repair, if has obviously been dropped in transit at some point as the legs are severely bent, and the chassis panels don’t line up. However, before wasting time on straightening it up, I wanted to see if it was working.
When testing a machine I don’t know, I assume it is full of dangerous faults and proceed carefully one step at a time. It is necessary to consider:
1. The mains wiring is incorrect and dangerous, with the possibility of incorrectly wired earth, poor earth connection to chassis, wire repairs with insulation tape, bare wires exposed inside casing, etc
2. Joints and hoses that leak and will spray water or hot steam on humans, electrical wiring, and your new flooring. This may not necessarily occur immediately, and may result from solenoid valves opening, pressure in the system increasing as it is heated, and so on.
3. Safety systems designed to protect you which are bypassed, faulty or non-operational.
First task was to check the electrical safety. This machine can operate on single or three phase, and so there is a diagram below the drip tray which shows the connections. The earth connection to the chassis was in place and well made. The mains wiring to the main isolator was in good condition.
For single phase wiring, the two live wires in the mains lead are coloured black, and the neutrals are coloured brown and blue. This wiring just fits in a British plug for testing purposes, but really a new mains cable is required corresponding the the standard UK colours of Brown (phase) and blue (live). The current draw in this configuration is 11A, so a 13A fuse is fitted to the plug. The wiring fitted the plug and it is safe for testing purposes.
The mains cable enters the coffee machine through a gland in the base plate, and connects to the main power switch. This has a protective plastic cover around it, and then has a metal protection plate above.
The switch has four positions:
1 (one element only)
2 (elements 1&2)
3 (elements 1, 2 & 3)
You can see the element here, with the three supply connections on the right. The three connections on the left are from the pressure-stat. You can see there are three element loops, allowing operation on single phase or three phase.
The output of the power switch (three switched live feeds) pass to the pressure-stat and then to the elements in the boiler. The pressure-stat has three contacts which are closed when the boiler pressure is below 1bar. The contacts open at 1bar, and then do not reclose again until the pressure is below 0.5bar. The pressure gauge can therefore be normally seen fluctuating between 0.5 and 1bar. It also means that the elements are powered whenever the supply is switched on, and the boiler pressure is less than 1 bar. If the boiler is empty, there is nothing to stop the elements coming on and burning out !
In positions 1, 2 and 3 of the mains switch, the control board is powered. This board monitors the water level in the boiler, and runs the pump and opens the fill solenoid to fill the boiler until the level probe is immersed in the water, at which point the pump and the solenoid are switched off.
In case there is a fault with the level detection in the boiler, the fill cycle only runs for 30 seconds or so. This does not normally matter, as pulling a few shots and steaming some milk will only require the pump to run for a very short time to replenish the boiler. If the boiler is empty, it is necessary to switch the mains off and on again a few times to allow the boiler to fill up to the probe level.
If the coffee machine has been sitting around for a while, the pump can seize up from under use. It can be freed-off by inserting a large screwdriver in a slot in the end of the pump shaft and turning the shaft by hand (do this with the power off).
By the way, when you turn the power on, the green led by the power switch lights after about 3 seconds (as does the red flashing one on the pcb). The pump does not start for a further 5 seconds.
After the power has been on for a minute or so, the boiler elements should be heard starting to sing. After 10 or 15 minutes, the anti-vacuum valve will start to weep a little and then should lift and seal the boiler as steam pressure starts to build.
The pressure gauge will indicate an increasing in pressure and at 1bar the pressure-stat should be heard to click open and the elements will stop singing. If left, the boiler will cool and the pressure will fall and at around 0.5bar the pressure-stat will close and bring the boiler back to 1bar.
If the pressure stat should fail to open for any reason (blocked pipe, split diaphragm, welded contacts, etc) the boiler pressure will continue to rise. At 1.5bar one or both of the pressure release valves on the top of the boiler will open to safety release the pressure before the boiler ruptures. Needless to say, if you witness this happening, switch the power off immediately and do not re-power until the coffee machine has been professionally looked at.
Opening the hot water tap draws water from the lower part of the boiler. Opening the steam tap draws steam from the top part of the boiler.
Operating any of the coffee buttons on the control panel runs the pump with the fill solenoid closed. Cold water therefore enters the boiler heat exchanger via the injector and is heated by the large body of water in the main boiler cavity.
This pressurised water, now heated, passes to the group. The solenoid on the side of the group is powered and allows the hot water to pass to through the screen and therefore through the coffee.
A flowmeter measures the quantity of water flowing, and stops the pump as soon as the required volume has passed. At the same time the group solenoid is de-powered, and allows any residual pressure above the coffee to be released to the drain.
The boiler can also be drained, before storage or transit, by opening a valve which runs to the drain (only do this when the boiler is completely cold). The group solenoid also runs to the same drain tray.