The Espresso Machine Restoration site
A non-commercial site for those interested in espresso equipment repair and restoration.
|La Marzocco 1 Group Linea AV
rebuild Part 3
|Some test shots
|Gicar control unit trouble
I mentioned earlier that whilst the machine had been on loan to a restaurant it had developed a problem with the
control unit. In fact when I plugged it in after the rebuild the unit died - but at least he went down in a blaze of glory.
When the autofil kicked in for the first time the relay inside blew up and was followed by that awful smell that only
burnt electronic components make.
I'll be the first to admit that my soldering skills are dreadful - but I did manage to find some suitable relays and
soldered them onto the board. I won't embarrass myself by showing a photo of my soldering efforts, but it does
work! This explains why in the previous photos the control unit was missing.
I wanted to play around with the metal finish to the back plate that covers the solenoid. I had polished it as you can
see in some previous pics, but it was still not perfect. So I though "what the heck" and gave it the circular brushed
pattern. I like it - but of course I can change it back if I get tired of it.
After I put the new panel back on the 4 panhead screws looked dull - so I just had to give them a quick polish! The
contrast of the polished screw and the brushed panel looks great.
Take your lengthened banjo tube mods and throw them out the window, there's a new group in town.
No seriously, take the best machine in the world, add an idea that has been hatching for about 4 years, a modified
solenoid valve, a brazing torch, a drill press, a day at the workbench and a lunatic Englishman. This is what you
The path the water takes from the group to the diffusor has been changed. I have eliminated any water exiting the
group and all pipes are inside the group. The head of the 3 way valve is also inside the group keeping everything
up to temp.
What are the shots like?
It appears to have stopped the initial temp. drop associated with the water exiting the group and back in again. I was
slightly concerned with the water hitting the coffee too soon (although water debit is the same as usual) since I
changed the banjo tube, but I have since added a valve between group and pump which is allowing me to come up
to 8-9 bars gradually rather than full on. When I flip the brew switch the pressure rises gradually and gets up to
around 8.5 bar after 5-6 seconds. It is too early to compare shots but visually they appear more rich and full.
|Final version I promise!.....07/02/05
Hmmmm pre-infusion. One of the benefits of having a 1 group machine is that you can adjust the water flow or
pressure or whatever and it doesn't affect any other group. I had already played around with pre-infusion on my P1
machine several months ago with a delay relay on the pump. After you hit the brew switch the group solenoid will
open and then you can adjust the time the pump comes on from 0-6 secs (you can adjust). Naturally it only works
with a plumbed in machine.
The 1G AV super machine was being run from bottled water but I wanted to play around with pre-infusion. The
valve I installed a few weeks back has been working very well but the pump pressure was still coming up too fast.
Then I started thinking about the Marzocco manual groups - the beauty is you can pre-infuse as long as you like.
Then I remembered a rocker switch I have somewhere....
So here it is, a pre-infusion isolation switch...
The left side controls the 3-way valve. Switching that on allows the coffee to pre-infuse under mains water pressure
(I have it set at 1.5bar). Then when you are happy with the pre-infusion flip the right side to switch the pump on and
it will build up slowly (my other valve) to 9 bars.
I only installed it this afternoon (and plumbed it in) and am still playing around with the time to pre-infuse. I will post
results in a week or so.
La Marzocco Linea 1Group AV
2300W 220V Single Phase
K-Type thermocouple & PID controller
Pre-heat module for brew boiler
Modified group valve
Pump pressure "ramp up" valve
Pump and Solenoid isolation valve EE Controls
Pump delay relay for AV controls
1 insane owner
|This website is created by Paul Pratt, Hong Kong 2004-5. If you would like to use any of the images or text I am sure
I will say yes, but please ask first!
Email me here.