Okay, I know theyre not a site sponsor, but Damian Court, the Sunbeam marketing manager sent me an EM6900 thermoblock fresh from their lab. I was looking for a good thermoblock to aid me investigate a few ideas and Sunbeam were kind enough to oblige.
I got the TB today. Im impressed. It is nearly exactly what I was after. I already have a couple of thermoblocks. One from my first espresso machine, which incidentally was a Sunbeam and one from a Krups machine. The Krups TB can be seen in my Faema, being used as a preheater. The old Sunbeam TB is just lying around, so I used it to compare with the new EM6900 TB. Both the old Sunbeam TB and the Krups TB share a common design which seems to apply to most cheap TB machines on the market. They are aluminium and hence corrode. They are light weight, so dont have a great deal of thermal inertia. They also use cheap thermostats to regulate the temperature. The result is very poor thermal stability.
In contrast, the EM6900 TB is built with a verticle coil structure using stainless steel tubing. The element is also a coil of smaller diameter that follows the water pipe. All is encased in a solid aluminium block. So you get the excellent thermal conductivity of aluminium, a decent thermal reservoir (in the solid aluminium), but the water is kept in a stainless steel environment. Nice. Moreover, the EM6900 is controlled with a digital thermostat via some thermal resistive device (Im not sure what type). This gives the EM6900 a very tight deadband. In the pictures, you can also see the group area on the bottom of the TB. It is covered in a black teflon-like polymer, in order to keep the water path aluminium free. The group of the EM6900 is steel.
This TB looks like the goods. Im going to mate it to a Bezzera group (shown in the bottom picture). It may require some machining of the TB. Well see. Then Ill control it using a PID controller and have a look at how well it performs. It shoudl be interesting.
Anyway, heres the pictures for the curious.