I restored a 40 year old Cimbali Junior

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Posts: 55
Joined: 1 year ago

#1: Post by Shawn- »

This is the machine

What it looked like before

There was obviously a bad group gasket and lots of hard coffee schmutz burnt on. The seller had the machine in storage for 6 years and when I went to look at it was the first time it had been used in all that time.
I brought beans and grinder and a scale. When I tested it I got a decent shot from it. I was even bold enough to taste the result and it was damned good in spite of the way the machine looked.

Next post shows during restoration.

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#2: Post by Shawn- (original poster) »

During disassembly and cleaning:

I did a thorough cleaning and descale. I had to use some pretty aggressive acids to clean the boiler and hard to reach passages inside the group since the off the retail shelf lactic acid solution wasn't touching the hard black scale. Fortunately, at work I have access to 80% Phosphoric acid. I diluted it to about 15-20% with hot water and even at that it took about 4 hours. I was cautious about this because I didn't want the acid to attack the brazing on the copper boiler. There was not much green in the pickling solution, which was reassuring since the presence of that would indicate dissolved copper.
Even with the aggressive acid pickle there was quite a bit of mechanical action (scrubbing) required.

The result:

I only had to invest about $275 Canadian. For that price I replaced safety valve, anti-vac, all copper washers, seals and o'rings and rebuilt steam and tea-water valves. Also replaced the Sirai Pressurestat with a 0.5 to 1.2 bar Mater and a 40A SSR (more on that next post).
$90 of that $275 was for paint.

Next post is upgrades.

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#3: Post by Shawn- (original poster) »

Replacing Sirai Pressurestat:

When I went to rewire the machine after plumbing and casework assembly I found the insulation to be somewhat brittle.
Out of an over abundance of caution I decided to replace all of the wiring.
I used 12ga wiring for the high current heat circuit. This wire was salvaged from a commercial dishwasher and is high- temperature and abrasion resistant insulation and the wire gauge is over-rated for the circuit ampacity (original wires were 14ga)
All the other wire used was silicone insulated (high temperature resistant) 18ga wire. Since the silicone insulation does not have the same abrasion resistance as the original pvc insulated wires, I encased most of it in woven sheathing to the lucifer valve and boiler fill solenoid.

For the pressure switch I ran a new wire from switched hot on the terminal block (TB) in the 'brain box' to common on the microswitch.
From NC on the microswitch to A1 (signal in) on the SSR (solid state relay)
From A2 (signal out) on the SSR to TB neutral.

The high current circuit is 12ga wire as described:
- TB switched hot to high limit switch,
- high limit to element,
- element to L1 on SSR,
- T1 on SSR to TB neutral

The wiring in this machine is very simple although I did find something about it that seemed out of place.

The original wiring layout had hot leads running to the components (solenoid valves, element, pump), and had the switches on the neutral return wires. I have every reason to suspect that this was original because of the labels that were on the terminal block, but it is not the safest way to wire since if the appliance were plugged in and OFF there would be live electrical conductors outside of the control box. I'm somewhat surprised that this device received electrical certification with this oversight.

I changed all that.

Now the 'line' or 'hot' connects to the switches in the control box so when the machine is plugged in with power off there are no hot wires outside of the control box.

Team HB
Posts: 5535
Joined: 16 years ago

#4: Post by ira »

Backwards wiring, "switched neutral," is common on espresso machines.

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#5: Post by Shawn- (original poster) »

More upgrades!

This machine was so basic.
- pourover with 2.5l tank
- button for manual boiler fill
- no water tank pressure switch (for low water sensing)

No electronic controls. Only 3 switches
- You turn 1 rotary switch for power on.
- Push a button to energize fill solenoid and vibe pump for boiler fill
- Turn another rotary switch to energize 3-way solenoid and vibe pump for brew on/off

The plumbing design is equally simple.

I appreciate the elegance in the simplicity of the design, but I have a few 'wants'
The simplicity does provide a good pallet for upgrades.

Obviously the already described Pressurestat replacement. The Mater has a smaller differential range so boiler pressure will be more consistent, and the SSR should address the problem of shorter lifespan of the Mater by switching the high current load and saving the tiny contacts in the microswitch from burning out.

I do not want to leave the machine with a manual fill. I think it opens up the opportunity to let the water level run too low and potentially damage the heating element.

And I don't like pourover. Particularly when I have a perfectly good water filter. It's a heavy machine to move out from under a shelf to gain access to the lid to fill. And the tank does not just lift out for cleaning.

So first up is connecting to water mains and drain..,

Tinkercad to design a drain pan for under the drip tray.
3D printed with black PETG.I'm fairly confident that PETG can handle the temperature of the small amount of water and I expect the water will be cool enough by the time it hits the drain pan.
If it doesn't work out I can use the same STL file and try printing in ABS

The pan was designed with 1/2" fpt threads for a fitting to connect the drain hose.

The vibration noise was too loud. So new mounts for the vibe pump, and Quickmill pulsor. Minor modifications to tubing locations so copper does not touch the frame.

Lots of room to work. I could very easily fit a rotary vane pump in here by relocating the boiler fill solenoid.

The hardest part of this was the fittings from the pump inlet to the water supply.
The brass fitting on the pump inlet and the short stainless braided hose were purchased and then I had to cobble together the rest from a small copper plate cut out of a piece of 2" pipe, a 1/8 male BSP x 1/4" female BSP fitting and a 1/4" npt street 90, all soldered together (silver bearing solder) so that the mismatched threads don't leak.
To be honest it was harder than it needed to be and most of the work was flattening the copper and cutting and cleaning it to look pretty.

Next step is boiler auto fill.

And I've already spent too much money so I'm too cheap to buy a Gicar

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#6: Post by Shawn- (original poster) »

Before I get to installation of the automatic boiler level control...

The water mains and drain connection is AWESOME!
I'm so very happy.

Cimbali Junior has a shallow drip tray and is a HX so every time I walk up to the machine whether I'm making 1 drink or 6 I needed to empty the tray at least twice.
I don't generally flush like this...
La Cimbali Junior S Brew Temperature/Flushing Regime
...but close enough.
The concern for me is not just cooling the HX, but heating that massive F'n chunk of brass.
But regardless, there is a lot of water involved in getting the temperature right.
I would flush usually 3 times before engaging the portafilter, and once after brewing.

1.) One long flush to purge steam, and run about 30ml after I get smooth flow (about 80ml of liquid total) to pre-heat the group and cool and re-fill the HX..
2.) Weigh beans...
3.) Approximately 20ml flush...
4.) Grind, WDT and tamp...
5.) Short flush of about 20ml and install portafilter...
6.) Brew...
7.) Knock out my puck and rinse the portafilter from the group (about a 80ml flush)
Wipe the shower screen and wipe out the portafilter and replace loosely into the group OR return to #4 and do next shot.

That's a lot of water.

Having a drain and not having to refill the tank is great!
And I have noticed a flavour improvement with the filtered water.

Have I said that I'm so very happy?

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#7: Post by Shawn- (original poster) »

Oh yeah!
I forgot to mention in my last post...

The machine doesn't rattle or buzz...

It hums.

The minor changes to plumbing, new pump mounts, and pulsor made a big difference.

Before doing this I couldn't decide which was more annoying, La Cimbali or Baratza Sette.

I can conclusively state that Baratza Sette is much more annoying!

Shawn- (original poster)
Posts: 55
Joined: 1 year ago

#8: Post by Shawn- (original poster) »

I've posted the auto-fill for the boiler build here.

Auto-fill for boiler on M20 Cimbali Junior

User avatar
Posts: 101
Joined: 13 years ago

#9: Post by jknotzke »


Excellent restoration !

I did the same two years ago on an 1982 Cimbali Jr. Looks very similar to yours.

The problem I am having now, and I cannot for the life of me figure out why, is the site glass for the boiler is completely full of water and does not represent how much water is actually in the boiler. I have ran that boiler nearly dry and the site glass level was all the way to the top (to the point that I cannot actually see the water level).

Normally, I would think it's scale, but I only use demineralized water. When I first put it back together, it would correctly indicate the water level.. But gradually it would rise and then slowly come back down as it cooled.. The time it would take for it to come back down would increase and increase to the point now where it appears to be stuck.

Any ideas ? I suppose I could take it apart again and have a look..

User avatar
BaristaBoy E61
Posts: 3548
Joined: 9 years ago

#10: Post by BaristaBoy E61 »

Stunning restoration!
Thanks for posting.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"