Cimbali D/1 circuit hack

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
User avatar

#1: Post by civ »


My year 2000 Cimbali D/1 (1800W, vibe pump, plumb-in, auto-fill, dosing device and sight-glass) has, like most other espresso machines, a button you press to start a shot.

Once started, should you want/need to stop the shot for whatever motive, pressing it again (this being the intuitive thing to do, really) will get you nowhere, unlike most other espresso machines.

This is because, by design, the pump will stop only if the volume set by the four position selector switch has been reached. Notwithstanding, it will also stop if:

a) you move the aforementioned switch to another setting.
b) switch the machine off ... =^ °

Here's the circuit diagram scanned from the D/1's manual:

From what I think I understand, pressing 'Pc' (brew button) sets it 'closed' momentarily, sending power to 'Ec' (group solenoid), 'P' (pump) and 'A' (relay coil) which sets 'a' (relay contact) to 'closed'. This sends power to 'Ce' (electronics box) where other relay/s take over, maintaining power to 'Ec' (group solenoid), 'P' (pump) and 'A' (relay coil) after 'Pc' returns to 'open' when you let it go.

Pressing 'Pc' (brew button) again while the pump is working will not do anything as 'a' (relay contact) will remain 'closed' till the water level set by 'Cd' (coffee dose selector) is met.

Does any forum member know if there's a way to get the brew button to work as in any other machine?

push --> to start brew till the level set is met or push --> to stop brew

Any corrections/suggestions/ideas will be welcome.

Thanks in advance,



#2: Post by movnmik »

My M30 Dosatron operates in the same way. Each group has 5 buttons - 4 dosing and one off/on. In order to stop a preset dose you have to press the off/on button and not the dose button you pressed to initiate it. My La Spaziale Rapid EK operates differently. You can start and stop any dose with the same button or the off/on button. I'm not sure why Cimbali opted this route but if there is a way to modify it to operate like the LaSpaz then I would love to try it out.

Cerini Coffee & Gifts: official US importer for Olympia Express
Sponsored by Cerini Coffee & Gifts
User avatar
civ (original poster)

#3: Post by civ (original poster) »

movnmik wrote: I'm not sure why Cimbali opted this route ...
It does not make much sense to me ...
To the extent of, when I first installed it, automatically and without a second thought insisting on stopping the brew by hitting the brew button a second time as I saw it go blonde.

Until I managed to get it into my hard head that it was not the way to go about it. =^/
movnmik wrote: ... if there is a way to modify it to operate like the LaSpaz ...
I'm sure there is.
The thing is how much work (change a relay? rewire?) it entails while not sacrificing any other functionality.
movnmik wrote: ... then I would love to try it out.
That would make at least two (or even three) of us.
There was a post last year about this same Cimbali feature:

Cimbali Junior D/1 vibe pump shot interruption

The only solution found was to use either the on/off or shot volume switches.
But it is rather counter-intuitive, isn't it?




#4: Post by Pim »

Hi Civ,

indeed that would make three of us. The quoted thread about shot interruption was mine. ;-)

Still haven't found another solution for the problem. But have encountered another problem. According to the manual (one sent to me through mail by Jorgen) backflushing has to be done by switching of the machine during a shot. This of course because there is no shot interruption.

The second time I did this my boiler would not stop filling. A problem I still haven't managed to solve. The solenoid valve is not stuck because once I disconnect it the boiler stops filling. The water is also hard enough for the probe to detect the water level. Only thing I can think of is the electronics, regulating the solenoid of the boiler fill. There lies the problem: I am not familiar enough with the electronics.. Now only on special occasions have I used this beautiful refurbished machine by disabling the auto fill.

Any suggestions? Also, could you (civ) send me the file with the electronic diagram, my copy is so poorly scanned that it is illegible. I'll PM you with my e-mail address.

Kind regards,



#5: Post by t3steve »

They have it hidden in this directory:


User avatar
civ (original poster)

#6: Post by civ (original poster) »

Hello Pim:
Pim wrote: Still haven't found another solution for the problem.
Neither have I ...
But it's on the short list.

I find it rather annoying (used to less expensive/elaborate home machines) that I cannot just turn on/off the pump, be it to make a ristretto on the fly or clean the screen/pf with 'just' a squirt of water.
Pim wrote: But have encountered another problem. According to the manual (one sent to me through mail by Jorgen) backflushing ...
I do my backflushing by putting a blind filter or equivalent and brewing a shot, which I cut short (as per the manual's instructions) by turning the machine off after a few seconds and repeat this a couple of times, waiting a few moments between each time. No problems ...
Pim wrote: Any suggestions?
I think you should try and make sure that all the connections to the boiler level probe are intact and that the probe is clean. It the autofill does not stop, it's as if the probe were disconnected.
I don't think it has anything to do with the backflush, but what do I know? =-/

I have only once encountered a 'similar' (in a way) problem: one day, for unknown reasons, the doser deposit would not fill up.

As the boiler's autofill worked properly, I knew it was not a problem of low water pressure at the mains.
I also double checked all the doser contacts and found that they were OK.

I then suspected a doser solenoid valve malfuncion, so with the machine 'unplugged' (read again: unplugged, ok?) I disconnected the lugs to the solenoid and connected them to 220v. At that point, the deposit started to fill so a solenoid malfunction (stuck or with a dead coil) was ruled out.

Not being low water pressure problem or solenoid malfunction the next thing was to follow the black cables to the electricals box under the drip tray, where you will find yet another much smaller black box labelled 'Gicar' and a large relay, among the switches, lamps, etc.

Before looking into the Gicar box which is (I think) directly related to the level sensors in the doser deposit, I wanted to look at the large relay, as it seems it is what gives power to the Gicar box and it's own relays and detectors. (any corrections to this assumption will be welcome)

My hunch was that maybe one of the relay's outer lugs was not getting current or that maybe the relay had stuck open or given up the ghost. I disconnected/connected all the lugs one by one and then gave the relay a good hard tap on the side.

Lo and behold ...
That did it. =-)

Either one of the lugs was not making a good connection (after all, they've been untouched since manufacture, this happens often with electronics) or the relay was stuck.

In any case, the routine worked.
If it was not this, I would have had to open up the 'Gicar' box to see what was up.
Pim wrote: Also, could you (civ) send me the file with the electronic diagram ...
I'll be glad to.
I have a cut down *.pdf I was making to send for storing it at HB in case anyone needed it.
It's now finished and has just what is needed to know the rig, the rest of the usual OEM stuff has been pruned for the sake of disk economy.

Hope you get the problem sorted out.



User avatar
civ (original poster)

#7: Post by civ (original poster) »

EDIT - Friday 08/17/2012 - 07:46 -03:00 GMT

The circuit modification described below worked from the start and continued to work as intended with no problem whatsoever up to late wednesday night, when a glitch developed, with no indication as to where or why it happened. 

I am presently in the process of looking into the problem and making inquiries with specialised techs in the Gicar control field to see what's up. I will post the results of my findings as soon as I get them. 

In the meantime, I strongly suggest that any intention of putting this circuit mod in practise be put on hold.

My sincere apologies to all.
I seem to have have found (at least for my particular Junior D/1) a solution for the rather annoying lack of an on/off brew switch, which made it rather cumbersome to control brewing and to backflush.

As always, YMMV as I have the idea that not all Juniors are made with the same components, but I think that the theory behind this circuit modification is sound and (with careful inspection) applicable to any of the older Juniors using this type of doser and Gicar box.

The Gicar box works in conjunction with the doser sensors and the water level sensor (SS rods) in the boiler to control the pump, the doser's water inlet valve and the boiler fill Lucifer valve.

The rods in the doser and the rod in the boiler fill well are either gounded by means of the water level (in the doser or in the boiler) or not.

In the case of the doser mechanism, depending on which rods are grounded, the pump will run or not and the doser's water intake valve will open or not. It's either one or the other, the pump does not run when the water inlet valve is open.

When the brew button is pressed, the pump starts working until the water level reaches the point where the selected rod is not gounded, then teh Gicar box stops it and opens up the water inlet valve, closing it when the water level reaches the point where ground is achieved by another sensor.

In my Junior D/1, the pump activation switch (labelled Pc in the diagramme previously posted) is a push on/release off DPST type, with only two of the poles connected to mains.

This modification uses the second (vacant) set of poles to connect/disconnect the ground that goes from the coffee dose selector (Cd) to the Gicar box.

In the original circuit, the cable that goes from the coffee dose selector to the Gicar box is gounded by whatever level (rod) is selected, letting the pump work until the water level goes below the length of the rod and ground is no longer present.

What I did was to interrupt this cable at the Gicar box, route it to the vacant pair of contacts at the switch (Pc) and then back to the Gicar box.

Once done, what happens is this:

When the Pc switch is activated, the pump starts to work (as originally intended) and ground (now intercepted by the switch when not pushed to on) is also connected and the circuit works as it had not been modified.

So as long as the button is kept pressed, the pump will work until the water reaches the level set by whatever level (rod) was selected.

But, if at any time before that level is reached the button is released, ground will be interrupted.

At this point, the Gicar will stop the pump and open the water inlet valve to refill whatever water was used from the doser. This allows full control of the pump, with only a 1.0s delay when the button is let go.

I'm sorry but I don't have any photos of this. I originally intended to take some but decided against it as it may (probably will) confuse anyone with a different configuration in their Junior. With the diagramme, a tester and the required tools, this modification can be done in 20' or less.

The usual disclaimers and warnings apply: practise this modification at your own risk and please take a minute to disconnect the machine from mains before opening it up to do any work on the electric circuits.