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VBM Domobar Junior brew pressure too high?

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  • level3ninja
    replied
    Higher pressure with all other factors the same means higher extraction. The other thing it does is increase the likelihood of channelling.
    If it's not the standard 9bar it should really be included in the recipe, as pressure is one of the factors influencing extraction. Sounds like you did the right thing though, hit the recipe and when it wasn't working went back to the author.
    Last edited by level3ninja; 3 days ago.

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  • anthonypiccolo
    replied
    Hey all,

    I just thought I'd follow up on how things have progressed.

    - Grinder was recalibrated
    - Added coffee sensor, ensuring I was brewing at 92-95 degrees. A flush before brewing for around 8 seconds will usually get the grouphead to ~91C so I'm assuming at the puck it would be. around ~93-94. Didn't seem to be a temperature issue though
    - E61 grouphead completely taken apart, cleaned and new pistons added. After doing this the backflush was still not coming through the exit chamber.
    - Added a new cam lever which completely fixed the above issue.
    - Lowered the brew pressure to 9.5 BAR

    After all of this still getting source / not nice tasting coffee.

    I spoke to. my roaster Small Batch about it and they confirmed I had the right recipe, 1:2 in 27-30 seconds. They said they think my brew pressure was way too. high, they told me they bre at around 7-8 BAR. I thought that was way too low based on everything I've read here, but last night I gave it a shot.

    Once I lowered to 8, the first shot I pulled tasted so much better.

    Why does brew pressure impact the taste of coffee so much?

    Also, I'm really glad I've been able to fix the grouphead with the drain chamber functioning perfectly again.

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  • Birkin7
    replied
    Hi, 4 weeks ago you first posted your problem with the VBM, numerous posts, suggestions, ideas to fix etc the problem still exists. Time to call in the cavalry and find an experienced espresso tech to sort your machine out.
    I would well and truly be having serious caffeine withdrawal symptoms by now.
    Maurice

    Leave a comment:


  • roosterben
    commented on 's reply
    When I had the some problem in my Rocket Giotto I bought a new 2 way solenoid (still sitting in my parts box as it wasn't the problem). After pulling apart the group a few times and checking each item against the old and re-assembling exactly to the parts diagram it started flushing correctly (as below I may have had to reposition the lever handle/cam but can't remember).

    Your lever if you pulled it off and replaced the o-rings and cam when you rebuilt your group, maybe you reassembled at a different position so it is not moving the E61 valves correctly which is causing a) Drips from not sealing properly and b) Not flushing properly from the backflush due to the lever handle or cam being out of position.

    When checking the lever I find it easy if you have removed the top nut on the E61 group to loosen the top spring with the mushroom. Then is it easy to check the position of the lever cam and make sure you have attached the lever handle in the correct position.

    Per your above comments you can easily remove the lever cam and have a look at it.

  • anthonypiccolo
    replied
    It's weird, after replacing the pistons with brand new ones with new gaskets, when I backflush and put the brew lever back down, I still don't get that pressure release and water exiting the drain chamber, I remember it would almost squirt out as the pressure was released. I read this online. Perhaps it's something to do with this as I have a brand new 3 way valve in my E61...

    Also in response to your comment @roosterbean - I'm sure the few drops leaking every now and then is probably because I potentially put a valve incorrectly, but I don't think I did. But the backflushing issue has persisted before I replaced these parts and continues to.

    Could it be the operating cam is worn down and therefore it never engages properly to allow the water to go through the drain chamber to begin with and open those valves?

    My group head won't flush when I put the lever down
    • Move the lever up and down and see if resistance is felt in any direction from the cam moving between actuators (valves). If it will not drain, and not much resistance is felt, remove the bottom of the E61 group head and inspect the actuators. They may be broken, or ground down from poor maintenance that the cam does not make contact with the top of the actuator.
    • Remove cam and inspect for flat spots. If the cam is ground down it may not be making contact with the actuator.

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  • roosterben
    commented on 's reply
    Well if it is dripping while making coffee and not backflushing properly you either put it together wrong or a part is not right.

  • anthonypiccolo
    replied
    Originally posted by roosterben View Post
    Re the drip from group and backflush not working normally, did you check that each E61 valve was specific for VBM Domobar Junior. The E61 group is a general design but each manufacturer has slightly different implementations. So if you bought a CoffeeParts E61 kit, not all the components will work in every E61 machine. If you have chucked out the old valves, pull the group apart and put each valve side by side with the old ones and make sure they are 100% identical. Other possibilty is springs in the wrong spot or valves upside down.
    Yep, I bought it from Talk Coffee and got the specific VBM parts.

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  • roosterben
    replied
    Re the drip from group and backflush not working normally, did you check that each E61 valve was specific for VBM Domobar Junior. The E61 group is a general design but each manufacturer has slightly different implementations. So if you bought a CoffeeParts E61 kit, not all the components will work in every E61 machine. If you have chucked out the old valves, pull the group apart and put each valve side by side with the old ones and make sure they are 100% identical. Other possibilty is springs in the wrong spot or valves upside down.

    Leave a comment:


  • anthonypiccolo
    replied
    Ever since I did the full e61 service, the temperature at the group gets to 105C and when I flush it's far too hot.

    I think because the group hadn't been serviced it may have been running cold, and that's when I moved boiler pressure up to 1.3 BAR from 1.2 - I guess now that the grouphead is serviced I can move the boiler pressure back down to 1.2

    Leave a comment:


  • Jackster
    replied
    Can you do a video?

    Shouldn't be leaking out the drain when making your brew, maybe a seal pinched, or something.

    Try tasting the brew water without any coffee. Wait till it cools so you can taste it properly. If it's not nice, there no way you can make a good brew.

    Are you saying your chemical backflush doesn't make froth out the drain? How can that be? Is it maybe backflowing into hx. That would likely give a gross taste after. Lol

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  • Boggas
    replied
    If your brew temperature is not way off, have you tried playing with different grind/yield? I love the science and reading aspect of the hobby, but if it isn’t working, change things up and let you mouth decide. Whenever I roast new beans I always pour 3 basic shots 1:1, 1:1.5, 1:2. Some beans are just more to my taste with a slow ristretto pour than a more traditional espresso pour. I am far from an expert, but my experience with curing sour shots is to slow the pour (grind finer). Pouring 20 grams in and 20 grams out in 45 seconds may not be typical, but if it tastes amazing I am happy.

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  • anthonypiccolo
    replied
    So did the E61 full service, all seals looked good, but replaced them anyway, and brand new pistons. Cleaned the mushroom (which was already quite clean) in a bath of descaler and then wire brushed it. Everything looked pretty good.

    Now when I brew a coffee I can see. the drain chamber drips as the coffee is brewing, is this normal? Obviously before I had 0 drips even when backflushing. Now when I backflushing I see some water dripping through as well. I don't know what would've caused any blocking. However, I do notice when I do a chemical backflush I don't see the espresso cleaner come through the drain chamber which I did a few years ago.

    Overall, there seems to be some water dripping through the drain chamber now which is good.

    I spoke to my coffee roaster (Small Batch) - they told me brew pressure for them is around 7 BAR, 95 degrees and 20 in 45 out for 27-30 seconds. So should I try adjusting my brew pressure to around 8 BAR? Seems far too low. Coffee still has sour taste no matter the brand. Maybe I just suck at this, doesn't seem to be anything inherently wrong with the machine

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  • Caffeinator
    replied
    Originally posted by anthonypiccolo View Post

    So I think the difference is absolutely no water comes out of the drain chamber when I back flush. No pressure is released so it's all at the puck and the portafilter is literally stuck there and I have to manage the situation to try and avoid an explosion there.... The shower screen has flown off before when trying to get the portafilter out. So there is clearly something wrong there.
    You have already been provided with the solution

    Originally posted by level3ninja View Post
    I wonder if that's what could be impacting the taste / sourness of my shots though.
    Nope- assuming it's clean and your technique is satisfactory, your machine is likely running cold (or the coffee is poorly roasted). Service time.

    Originally posted by anthonypiccolo View Post
    I'm in Melbourne, so can't really go get this fixed right now. I'd like to try myself
    Not so. A little research will provide info that pickup/dropoff is available in Melbourne under Stage IV restrictions, so you can easily have your machine serviced if you are not inclined to do so yourself.

    Skimp on service on the Domobar Junior and it bites....wallets. Don't say you weren't told.

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  • anthonypiccolo
    replied
    Originally posted by GaryM View Post
    There are some good diagrams out there of the e61 group. The valve will be back behind the brew head somewhere. Water flows in from the top and down when brewing. When I back flush my Junior it will release pressure when I push the lever back down, but it's not a violent purging... Water just flows out of the bottom of the group into the tray below. There is still some pressure left on the Puck.
    So I think the difference is absolutely no water comes out of the drain chamber when I back flush. No pressure is released so it's all at the puck and the portafilter is literally stuck there and I have to manage the situation to try and avoid an explosion there.... The shower screen has flown off before when trying to get the portafilter out. So there is clearly something wrong there.

    I wonder if that's what could be impacting the taste / sourness of my shots though.

    Leave a comment:


  • GaryM
    replied
    Originally posted by anthonypiccolo View Post
    What is the 3 way? Is is the bottom part where the drain chamber is? Or is it in the mushroom cap at the top? I'm in Melbourne, so can't really go get this fixed right now. I'd like to try myself
    There are some good diagrams out there of the e61 group. The valve will be back behind the brew head somewhere. Water flows in from the top and down when brewing. When I back flush my Junior it will release pressure when I push the lever back down, but it's not a violent purging... Water just flows out of the bottom of the group into the tray below. There is still some pressure left on the Puck.

    Leave a comment:

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