Problem with wandering pressurestat on Cimbali Junior DT1

[Scan_cimbali]

I bought my La Cimbali Junior DT 1 last summer and after it was plugged in to the mains it has given me (and my girlfriend) many a good espresso moment. Due to the water hardness here in Denmark I installed a serious descaling filter as I installed the machine - so there shouldn't be any scaling issue. I have also, in my opinion anyway, given the machine tender loving care regularly..
Recently I noticed that the pressurestat which, when idle, used to hover around 1,0 bar has started to vary between 0,6 -1,2 bar. It is not oscillating wildly between these two extremes when it is idle, but rather it falls slowly down to about 0,6 bar and then brings the pressure up to about 1,2 bar before the cycle starts over. Again, this happens slowly and takes several minutes.

Otherwise the machine works just fine and I haven't noticed any other problems. I just want to nip this in the bud if this is the first sign of trouble with my beloved machine!
Seems to me that there must be a problem with how the machine reads and/or responds to pressure in the boiler..?
I'd be really grateful if there is someone out there with some ideas on this!

[Ken Fox]

Most probably your Cimbali OEM pressurestat will need to be replaced. In my (not very humble) opinion the pressurestat Cimbali now uses is a POS; mine needed replacement just before the warranty on the machine ran out. The good news is that you can replace it with a Mater, for a lot less money than the Cimbali. The Mater is also a POS but it should last a couple of years.

If you really want to resolve this issue on a long term basis, I suggest you consider putting in electronic temperature control, most probably via what is called a "PID" controller. This will require some research on your part and some fabrication and installation skills to get done. After doing this I have been able to attain tight temperature control on my machine, rivaling the temperature control one finds on the newest double boiler machines.

Here are some links on this website to what I have done with my Junior DT 1 that may be of interest.

Should I PID my Heat Exchanger?
Pictures Of Modified Cimbali Juniors

(note that I own both a DT1 and also a 10 year old vibratory pump pourover; both have been modified)


If you should become interested in further "hacking" your DT1, these threads may also be of interest.

The Impact of Preinfusion on the Taste of Espresso Shots
How to Preinfuse; Extraction Pressure Redux

There is a lot of material on the internet and on usenet about PIDing espresso machines; you basically just have to start looking and the more you look the more you will find!

Good luck.

ken

[Scan_cimbali]

First of all, thanks for the advice! In addition I read some of the replies to the post: Pressurestat surgery on Cimbali Junior.
I thought I could hear the switch in the pressurestat clicking when the pressure went way down and concluded that though the deadband is way too large, the switch itself must work. Therefore I thought that maybe, as the above post suggests, the mechanical lever in the pressurestat device is operating with too much friction. I opened the machine (after disconnecting everything) and tried to carefully move the lever up against the spring. Sure enough, I think the lever grated a little bit against the rod inside the spring. One drop of sewing machine oil on the rod and I could feel the lever moving with much less friction. Reassembled the machine, turned it on, and waited.
I've now had it on for 12 hours and the pressure gauge is rock-steady, back where it used to be!
Problem solved!

Jarle

[Ken Fox]

First of all, thanks for the advice! In addition I read some of the replies to the post: Pressurestat surgery on Cimbali Junior.
I thought I could hear the switch in the pressurestat clicking when the pressure went way down and concluded that though the deadband is way too large, the switch itself must work. Therefore I thought that maybe, as the above post suggests, the mechanical lever in the pressurestat device is operating with too much friction. I opened the machine (after disconnecting everything) and tried to carefully move the lever up against the spring. Sure enough, I think the lever grated a little bit against the rod inside the spring. One drop of sewing machine oil on the rod and I could feel the lever moving with much less friction. Reassembled the machine, turned it on, and waited.
I've now had it on for 12 hours and the pressure gauge is rock-steady, back where it used to be!
Problem solved!

Jarle

Glad to hear it worked out for you. My impression of the Cimbali OEM pstat is that although the electronic parts seem fine, the mechanical lever portion looks to have been produced by an Italian teenager with a couple of pairs of pliers and a tinsnip. The second one I received was basically unusable until I manipulated it, not unlike what you did with yours.

The ultimate solution, however, is to just bypass the thing by putting in electronic temperature control (PID).

ken