Mazzer Mini-E Doserless: Distribution and Static Issues

by Mole : 3rd Dec 2007

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Problem: Shots are channelling and there are grinds sticking to the metal case and funnel of the Mazzer Mini-E Doserless.
Solution: [Tentative] Grinding too fine (possibly because of old burrs) causes clogging and static. Also, there was a possible poor mains connection (the earth) which could have caused static and poor distribution from the funnel.

For more information, read on…

History of the Problem

DaveC always advocates simplicity in the preparation of espresso-based drinks. No stirring of grinds in the portafilter after grinding; no particular distribution method above a simple rapping of the portafilter against the palm of the hand; no special tamp; etc. So, I've been trying to reduce the complexity of my process to a quick and simple routine. On the whole, this approach had been working for me, until recently when I had been noticing an increasing problem with static on our Mazzer Mini-E Doserless. Coffee grinds were leaping energetically from the basket whilst grinding and sticking to both the backplate of the grinder and the outside of the funnel. Certainly not as bad as some photos I've seen on the web: a Mini-E owner had removed the wire grid to make cleaning easier (don't do this!). However, it was getting annoying. I wouldn't have bothered trying to correct this issue of itself, but at the same time I had been having serious problems with channelling in my shots. Every shot would channel and even stirring the grinds wasn't helping as much as it should. Not only that, but the grinder chute would easily clog up after grinding coffee for a couple of shots and need clearing with a cocktail stick. Not good.

Diagnosis and Testing

My initial thought was that a thorough clean might help. So, out came the vacuum cleaner, cocktail sticks and screwdriver. I had cleaned it before, but this time I removed both burrs and cleaned the whole grinder completely. Of course, this didn't fix the problem. Within two shots being ground the static had returned and the channelling was as bad as ever. D'oh!

Fed up with my inability to pull a decent shot at home, I cried (literally) for help from DaveC: "Could I bring the Mazzer over and try it with your Alex?"

"Go on then," came the reply.

Excellent! So off I went to DaveC's place with grinder in hand. We set up the grinder next to his almost identical Mini-E Doserless and pulled successive shots from both grinders using the same coffee. Not unusually for DaveC, he found both grinders to produce identical shots with little channelling and no static. After some rather choice expletives and a rant along the lines of "Dave, you [insert expletive here], how come everything always works for you?", I calmed down and we discussed the possible causes. The distribution problems could well be related to the static issue. But why would I be getting static at home, yet none at DaveC's place? The only obvious thing we could come up with was a dodgy electrical connection (probably a bad earth). This might mean (amongst others):

  • a bad socket in our kitchen (with a poor ground),
  • a problem with the wiring or (European) plug on the grinder,
  • a problem in the European to UK plug convertor, or
  • simply a bad connection between the European plug and the convertor.

Of course, the simplest solution would be to try another socket in the kitchen ;-)

Final Solution [Tentative]

So, of course, that's what I did. Lo and behold, the Mini-E is now performing as new again! No static to be seen. No grinds floating away and sticking to the case, nor spreading over the worksurface. Most importantly, there is now much less channelling and far fewer spritzers than before, even when doing the simple grind/rap/tamp technique that I had been practicing.

This is not to say that we've truly identified the real cause of the issue. Perhaps there is a dodgy connection somewhere else that's been fixed by simply moving the plug to a different socket. However, until I next need to clean the grinder, I'm tempted to leave a working machine well alone! If I do discover the real cause then I'll update this page, but the moral of the story is that a simple problem with static can cause major and almost unrecoverable distribution and channelling problems. Weird? Most definitely! :-)

Solution Update (6th Dec 2007) [Tentative]

The problem has yet to return, so I am hopeful that it is fixed. I've now completed some basic tests of the earth connections in the electrical sockets of the kitchen. To test the socket I thought was bad, it was simply a case of testing the resistance of the earth against another socket's earth connection using a multimeter (and leaving the sockets switched off!).
[Of course, I do not advocate doing this unless you are comfortable with such tasks!]
If there is no real resistance between the earth connections then it is unlikely that the socket is bad. As it happens, there does not appear to be a problem with the socket I was using as there was virtually no resistance between the earth connections. To confirm this, I have now used the grinder with the suspect socket and the static issue did not return.

The next step was to check the convertor. Whilst taking the convertor off the European plug on the Mazzer I noticed that it felt as if the plug could possibly move and become slightly disconnected from the earth connection. This could well have been the problem, which would explain why moving the grinder to DaveC's place seemed to fix the issue. Fortunately, the earth connection is just a strip of flexible metal which could be bent easily away from the case of the convertor, making a much firmer connection with the earth on the European plug. So, I am pretty sure that this cannot cause a problem in the future (if it was indeed the issue in the first place!).

A more permanent solution would be to have the European plug replaced with a UK 3 pin plug to avoid problems with the connections altogether. Of course, an appropriate fuse would need to be used (speaking of which, I have no idea why a 13A fuse is currently in my convertor when a 3A or at worst 5A fuse would suffice).

Solution Update (14th Mar 2008) [Tentative]

Well, so much for that! After some time, the static returned, but not as badly. I still have no real idea what causes it. To make sure the plug is good, I've now swapped the convertor for a proper 13A rated UK 3 pin plug to which I fitted a 5A fuse (I see no need for a 13A one). I've also tried replacing the burrs, as I've been having some problems with channelling and spritzing even without static from the grinder. The new burrs have not helped with the channelling, but seem to need a coarser grind than the old pair, which itself improves conditions in the grinder. I think that too fine a grind causes clogging and unless the chute is nice and clean it can lead to static. But then again, who knows…

Perhaps the moral of this article is merely to help identify areas to look at if you suffer from static in your Mini-E.