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Thread: VBM Jnr Temp/Pressure Adjustment?

  1. #1
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    VBM Jnr Temp/Pressure Adjustment?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hey Guys,

    Got a VBM Junior delivered from Coffee-A-Roma after an upgrade from Silvia. Wow - what machine.

    After a couple of weeks I am still struggling to get the honey like consistency I was getting with Silvia, 30 min warmup, fresh beans, VBM stock double basket, approx 19g of grind, flattened flush with ridge (very top of the basket), tamped etc as per Silvia routine

    Wondering if I may need to adjust the pressure? I noticed that during extraction the pressure guage starts around 1.1 bar and slowly moves down to around .9 bar - my understanding is that the result of that may be water that is not quite in the 90s (degree C). Do these things come from stores already adjusted? Did other owners have to tinker?

    Maybe I am overdosing as well? Do others find that with the stock double you need to level below the basked ridge (top)?

    In terms of crema levels, what kind of crema % should I be chasing?

    Open to other suggestions/tips etc

    Thanks Guys,

    PP

  2. #2
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    Hi PP,

    You should not have to adjust the pressure settings. Coffee-A-Roma should have checked it out before shipping. The pressure gauge should hit 9-10 bar during the extraction.

    I would suggest weighing coffee grounds in the basket and the espresso in the cup. Aim for a 1:2 extraction in 25-30 seconds. So, 19gm of ground coffee should give you 38gm espresso.

    The only variable you need to change is the grind of the coffee.

    To check if you are overdosing, place the tamped coffee in the group head, remove, and look for coffee on the shower screen.

    Crema will depend on the age of your beans, I would not be too concerned about the quantity of crema.

    Cheers,

    Sam

  3. #3
    Mal Dimal's Avatar
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    Think you might be looking at the wrong pressure gauge there PP...

    Brew Pressure should be within the range of 9.0-11.0 Bar as indicated on the gauge.
    What you're reading seems to be the Boiler Pressure Gauge, which typically operates within the range you typed in your post.

    As Sam suggests, I doubt that the VBM would have left the premises improperly calibrated and set up. You could always contact Coffee-A-Roma and seek advice from them, that's what I'd be doing...

    Mal.

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    Thanks Sam - I'll take a look at the shower screen. I know that my pucks have a clear impression left on them, and the 10c piece test leaves a 1 or 2 mm indentation.

    Mal - Yep sorry I meant the boiler pressure. Randy's domobar guide shows:

    Boiler Boiler Approximate
    BAR temp brew temp
    1.0 - - - - 253 F. (123 C.) - - - - 196 F. (91 C.)
    1.1 - - - - 255 F. (124 C.) - - - - 199 F. (93 C.)
    1.2 - - - - 257 F. (125 C.) - - - - 201 F. (94 C.)
    1.3 - - - - 259 F. (126 C.) - - - - 203 F. (95 C.)

    which makes me wonder if I am running it through a little cool at the basket. A bit of sourness also raises my suspicion.

    Thanks for your advice!

  5. #5
    TOK
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    Hi there.
    Owners, especially new owners, are not qualified to start second guessing the set up of the machines they haven't yet got to know, and HX machines are not really tunable to the nth degree as the table would appear to suggest (especially by the owner after doing only a little light reading).

    These machines cycle up and down, the table is too definitive, suggest not to take too much notice of it

    You should also note that most smaller HX machines in this market have actually been set to run in the cooler end of the range deliberately, because discussions in forums have dictated that cooling flushes are "bad". This shows how the level of understanding of how HX machines work does not match up with the amount of technical data and client expectation (from reading too much but no understanding enough), that is out there...

    If you want something that responds much more responsively to "tuning", you will need to trade your machine on a dual boiler PID machine (and accept that experience shows that most people that buy these, actually leave them set on the originally delivered setting forever instead of using the capability that has been provided...ergo wasted money...).

    Your machine is set the way it is set and works the way it is intended, and it seems you are trying to read too much into what you are....reading. Suggest stop reading diagnostic stuff because it only just serves to confuse new equipment owners at a time when they are trying to work out the new equipment.

    Any problem with brewed coffee will likely go straight back to operator technique which = operator understanding of the new equipment.

    That said, these types of E61 Heat Exchanger (HX) machines are very very forgiving compared to something like a Silvia, so anyone that worked out a Silvia to get the great results they are capable of when used expertly, should have no problem with the object of this thread.

    Reading between the lines in the first post, I can see that something is amiss. From the comments made concerning the volume and weight of the grinds, off the cuff it would seem that the grind is way too coarse. Also it seems you may be over dosing. But very difficult to know unless standing with you in front of the machine.

    Without going into too much detail, I would say grind needs to be finer and dose smaller. The finished tamped dose shouldn't be any higher than the top of the groove that locates the filter circlip. Without measuring exactly, that will be approximately say 5 to 6 mm BELOW the actual top of the filter. And unless you are grinding/dosing/tamping correctly you cannot make any observations about the machine setup and operating temperatures because the resulting brew will not be representative of what the brew would be like when operator technique is spot on.

    Additionally, the party who you should be leaning on for any help that you feel is required, is the vendor. They takes yer money, so they should be delivering on the after sales service that they have obliged themselves to provide as a result.

    Hope that helps
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  6. #6
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    Thankyou TOK - great response.

    Just part of the troubleshooting process, I will focus on the dose for a while and see how I go, I also get the feeling that 19g may be a bit too much for this basket.

    Thanks again.
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  7. #7
    TOK
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    Thank you.

    Throw the scales away....the dose is volumetric at around the top of the circlip groove as stated above.

    And you will get roughly 19 grams anyway, given that if you are grinding too coarse and overdosing, as you grind down finer the puck will shrink down but still carry the same approximate weight for THAT sized filter (which should be the std Oz market commercial filter (deeper than the Italian "home" market filter so also call the Oz filter the "export" market filter). It will hold anywhere between say 18 and 20 grams depending on how fine you like to grind for the individual machine.

    Again...throw the scales away. The dose is volumetric to the same level regardless of fineness of grind and weight of tamp. There will be shock and horror from the front stalls, but that's just the way it is

    Hope that helps.
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    It does - thanks!

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    I got a Domobar Jnr about 4 months ago.
    I found I was often overdosing, I need to be tamping so that the tamped coffee is just on the line or just below the line of the ridge in the basket.
    I was overdosing and disturbing the top of the puck which caused channeling and sour underextracted coffee.

    I got the 18g double rancilio espresso parts basket from Coffee A Roma. In that basket I put 19-20g depending on the day, usually I am just below the ridge line.
    With the stock double 14g I think I was in the area of 14-16g and under the ridge line.

    Drew

  10. #10
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    Thanks Drew - so you knew you were overdosing by looking at the puck afterwards and also the taste?

    As you can see in the history of this thread, the advice I have been given is dose by volume and not weight. The trouble I am having with that is what I did with Silvia (dose till a mound, flatten over the basket filling any gaps without direct pressure) appears to be overdosing the VBM double basket (above the ridge). Interestingly, the instructional videos or here How to Make Coffee - Coffee Machine Steam Grinders Makers Commercial Domestic Italian Automatic show Scottie filling the basket with what appears to be a fair way over the ridge as well, using a similar technique.

    I guess my question is, if I don't weigh, then how can I keep a consistent dosing technique without overdosing? (as i found the silvia technique easily reproduce-able)

  11. #11
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    You can do it either way really.

    I dosed using the method in that video and found I was overdosing, that kind of thing can be quite susceptible to how you bend your finger (mounded up or down), when you bang the grinds down the first/second time,etc.

    I find using weight to be pretty reliable, basically I chose a blend of coffee to use for a few weeks, I then weighed the exact dose recommended at approx the correct grind and then used the old 5c coin on top of the puck trick to determine my dose, I found on the 18g basket I need about 19g coffee for the correct extraction.

    Now I've got my technique sorted I can change beans and very quickly know if I need to add another gram or so forth based on how far down the tamper rests in the portafilter once ive tamped. Sometimes I need to put 20g into the 18g basket for certain roasts/grinds so I just do that.

    I suggest weighing during your experimentation and getting used to a knew machine is a very good way to help get familiar with your machine. It is very very rare (perhaps once a fortnight) that I dont get a great shot out of my machine, the VBM Domo Jnr has proved to be a very reliable machine in the 4 months ive had it.

    Drew
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  12. #12
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    Thanks for your reply Drew.

    I also thought it looked like the video was overdosing. But then I thought - if it's good enough for him, then it's good enough for me!

    Might experiment with the 5c piece. I am right in thinking it should leave a slight indentation once locked and loaded yeah? No indentation = underdose. Massive intrusion = overdose???

  13. #13
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    Correct.
    Also if there is an indentation without the 5c piece then you could be in trouble.
    I found i was basically scraping the top off the puck and disturbing the surface before brewing was leading to massive channeling.
    Underdosing in my experience is less of a problem than overdosing where you destroy the pucks integrity before you begin.

  14. #14
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    Right.

    Did the 5c trick this morning and was pleased to see a small indentation, not the whole coin, but a noticeable indent. No other showerscreen mark noted.



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