VBM Junior HX wiring diagram anyone?

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

#1: Post by Just Mike »

HI everyone
I have a Vibiemme Junior HX which has been a great machine. Ive replaced some connectors due to melting - seemingly a common problem from high resistance connections,but simple jobs. However recently it started to 'smoke' and not from the same melting connectors. Seems the issue is related to Pin 5 of the relay (pic wont load Im afraid). I replaced it (most things with scorch marks are the problem) but the new one had the same issue so I quickly turned it off. The issue is further on or further back.
Just through wire tracing this pin seems to run down to the main on off switch but its a little difficult to see further as it is so tight. I thought maybe its the heater element shorting but that measures as 7.5 ohms, lower than the 9 ohms I see on line but hopefully not enough to cause an issue.
So - anyone had a similar problem or can predict the issue? Alternately (or even preferably), does anyone have a wiring diagram? I only see domo super online and its different enough to be unhelpful.

I need coffee and my wife thinks I should get a pod machine as back up - so please help stop 2 disasters :)


#2: Post by WWWired »

Hi Just Mike :) Great progress already by the sounds of it! There are some true geniuses related to the Vibiemme Domobar Junior here and no question there will be some great information related on the way soon :) . . . here's what is hopefully a correct excerpt from page 30 of the VBM Domobar Junior HX Instruction Manual showing the Electrical Schematic (Credit: Vibiemme srl), which is found at fantastic Home-Barista sponsor 1st-line Equipment one of the best espresso equipment companies on the planet! . . .

. . . and here's a fantastic video from 1st-line Equipment showing the incredible Vibiemme Domobar Junior HX machine for anyone interested in getting a look at this brilliant high-quality espresso machine :) . . .

. . . and here's a link to another superb Home-Barista expert espresso machine & equipment supply company, <Stefano's Espresso Care>, page on the Vibiemme Jr. HX - Electric showing an internal drawing along with several electrical components for the VBM Domobar Jr. HX sourced by Stefano's Espresso Care. Note: At position #9 of the model shown there is a Power Relay ("Viebiemme Relay Relpol"). These Power Relays are designed to "Ride the Lightning" and regulate/control/take-electrical- hits for the team (espresso machine team that is) and as can be seen in the great photos posted by Stefano's Espresso Care often have a clear housing, that allow for inspection of the internal Contacts and Terminals and sometimes worth an inspection to see what state they are in. It appears many maintenance schedules for top-quality espresso machines may often recommend careful inspection and replacement as needed of any Power Relay that is showing evidence of reaching the number of rated transfers/pole flips.
Here's a bit of annotated information from Stefano's Espresso Care incredible website/source for espresso machine components and much more . . .

Just Mike (original poster)

#3: Post by Just Mike (original poster) »

Thanks very much for the schematic, its still a bit conceptual but certainly a great help. On second thought yesterday I wondered if the resistance at 7.5 ohms was still an issue - that would give a current flow of 14.7 Amps vs the expected flow of 12.2 Amps. The device isnt tripping fuses or just not working - suggesting an increased flow of current through this part of the circuit. But I dont know the effect of scale or time on heating elements. Perhaps with heating this differential in the heating element increases even more. Any thoughts on this anyone?
Once I have studied WWWireds helpful schematic, if there is no apparent issue I will pull the heating element and see.

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Team HB

#4: Post by Jeff »

Have you already checked that there isn't path from the element terminals to ground?

The upper schematic looks pretty standard for machines of this class. It doesn't show a relay for the heating element, with the pressurestat taking the full load. The miniature pressurestats (CEME, MATER, ...) don't handle that well. If yours doesn't have a relay, adding one might be a good project at some time. The lower schematic (Stefano's) shows a relay and is probably a later version.

The relays in the Gicar controllers are often not the best when used on 120 V to directly control the heating element. While they are probably suitable for 230/240 V use, 120 V doubles the current, pushing close to their rating. Some manufacturers and models either skip the Gicar relay entirely (typically pressurestat machines), or use the output to drive an external relay (especially for PID-driven machines, often an SSR).

Just Mike (original poster)

#5: Post by Just Mike (original poster) »

Thanks Jeff, again very helpful
Fortunately I do have a relay and this is the part that is struggling with the load and generating a burning contact (soot is from the plugs plastic surround deteriorating with heat it seems). See attached.
I hadnt checked leakage to earth from the heater element - I suppose you are suggesting the scale itself might be doing that (as a metal salt)? Regardless, Im getting closer to having to remove the heater element.
Maybe Im learning my lesson about hard water as well...

Team HB

#6: Post by ira »

So from the mounting location of the relay, I'm guessing it was an after thought to keep the pressurestat or the relay in the Gicar box for dying when the switched from 240 to 120. I would remove the relay socket and see if it's not turned to carbon and causing a short between the socket and frame.

If I was guessing the relay has 4 or 6 wires going to it, the 2 that used to go to the heater now go to the relay coil and either 2 or 4 wires use the NO contacts to connect the heater to power.


#7: Post by fsatira »

I am a long time owner of a VBM Junior HX (~14 years) and have gone through similar issues with wiring connectors, mechanical relays and pressurestats burning out. With the help of EricS, we mapped out a schematic of the wiring. Unfortunately, I cannot seem to locate it! If i can find it I will post it.
We also used the schematic posted in one of the previous posts. This enabled me to figure out that my machine (2009) was wired with line and neutral reversed, which explained the random GFI trips. Once corrected, it has been fine. The wiring also helped me modify my machine in a few ways:
-I ran an SSR to switch the heating element and take the load off of the pressurestat. After burining through 2 expensive Jaeger stats, with the SSR (40A), I am using a Mater 110, which has not complained for the last 9 years.
-I eliminated the mechanical relay (plastic cube) entirely. The only purpose on my machine was to switch off the heating element when a boiler fill was called for. I instead placed a SPST switch under the machine to switch the boiler in case it is completely empty. For day-to-day, the water level does not go to the level of the element during a boiler fill call. The big reason to have the cube relay is during initial fill so the element does not burn out.

I still have the occasional quick connector to replace, but not nearly as frequently as before. I also have changed some of the wiring to more robust 16ga silicone, and 14ga for the heating element.

My machine has the older ProLind control box, and the heating element was originally switched by the pressurestat, there is no relay that switches the element. MY control box only has a relay to control the pump and solenoid for a boiler fill situation.

I hope this helps,




#8: Post by WWWired »

fsatira, ira, Jeff and Just Mike all raise very interesting issues about electrical termination and wiring assemblies inside quality inside highest quality espresso machines :) Vibiemme and all other top quality espresso machine companies go to extreme lengths to achieve highest specification wiring standards in all their exceptional machines. As the videos below show, these exceptional espresso companies can often be found to deploy only calibrated professional crimping equipment and undertake significant training of their staff to ensure perfect crimps and wiring assemblies. Such companies often will randomly sample Wiring Terminations/Fast-On connectors and assemblies, including taking cross-sections of crimps, to microscopically assess quality. Any wiring issues in a top quality espresso machine would likely be traceable to a new or inexperienced employee (possibly at a contractor) associated with manufacture of wiring assemblies/connectors in need of further training and mentoring to ensure terminations are perfect every time. Here's a superb YouTube video by TE Connectivity about Crimp quality in our Fast-Ons and other connectors and there is no question that all the highest quality espresso machine companies employ these practices diligently . . .
Credit: YouTube and TE Connectivity

. . . and here's the Advanced Crimp video from TE Connectivity on YouTube as well . . .Crimp Theory Fundamentals: ADVANCED

Regarding the Power Relay, many top espresso machines employ a high specification advanced Power Relay. Here's a link to a HB post showing the effects of multiple energizing cycles in a Power Relay: Replace Nuova Simonelli Oscar 1 boiler with Oscar 2 boiler

Just Mike (original poster)

#9: Post by Just Mike (original poster) »

Update - I still have not yet identified a definitive source for the issues with my VBM, but it is becoming increasingly likely that this is an issue with high current that was on the borderline before now 'tipping over' and leading to concerns. High heat in the assembly doesnt help. I havent yet removed the heater element and am waiting on a new relay socket at the old one is toast - the affected pin holder is completely degraded.
Although the VBM (and no doubt other good manufacturers) do use quality equipment, my sense is they are European, and have designed all their electrical specs around 220 V, and when adapting to the US market have made do with largely the same wiring harnesses and components. But the double current for high power elements (like the heater element, associated relays, and connectors) takes multiple items too close to their failure point - there just isnt enough headroom. A machine is tested and is fine on departure from the factory, but it doesnt take too much for a crimped connector to develop an ohm or 2 more resistance and start to heat up and create a spiral that leads to melting and failure. As an example - there is just one wiring harness for both models - yet the amperage would suggest this should not be the case - unless they engineered for worst case plus a margin of safety, and my sense is for the US market that margin of safety is minimal.
I still love my VBM and think its a great machine, but the electrical side at least would warrant a rethink. If I didnt have a background in tinkering there is little chance I could fix this this time (or the previous times). Yes I can take it to a repair shop but this is a heavy beast, not easily transported on public transport, and for a qualified tech, not a cheap job either. Especially given the lack of available accurate specifications and up to date, labelled wiring diagrams, there is a bit of guesswork involved. VBM could do better.


#10: Post by fsatira »

Hi Mike,
I completely agree with you. The parts are underspecced for the 120V we use in North America. I got rid of the Relpol cube relay since it was only rated to 10A, and found it impossible to find another rated for 15A. The current draw for the element is about 13.3A, so it will eventually fail sooner than later, with the melting of the socket as well.