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Thread: Loud vibe pump problem

  1. #1
    Senior Member
    Join Date
    Apr 2005
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    1,176

    Loud vibe pump problem

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    My BZ35e has been plagued with a screaming LOUD vibe pump. I knew this wasnt right because a mate has the same machine with a much quiet(er) vibe pump. The pumps are Fluid-o-tech units and are usually found in the more expensive machines (as these pumps are slightly more expensive). They are advertised as "quiet" pumps. Well mine wasnt.

    So I bought a new pump and refitted it. I also paid attention to pipe routing and replaced the rubber pump mounts.... but no change....

    I cant emphasise how loud this thing was running. I was almost considering putting it on ebay, or retrofitting a rotary pump.

    Anyway, the clue was my mate saying that he thought my pump had a much higher pitch. When I listened to his I agreed. Id estimate about twice the frequency (ie rather than 50 Hz, more like 100 Hz).

    Vibe pumps are basically all the same design and they all use a diode to rectify the mains ac power, meaning they only use half an ac cycle. The difference with the fluid-o-tech pump is that the diode is found in the plug, not in the pump body, like an Ulka or Eaton pump. So the other night, I put my coffee craving on hold and dismantled the plug attached to the pump and checked the diode with a multimeter. Sure enough, the diode had shorted. Viola! So scratching around in some old circuit boards I found a nice big diode with a similar rating, removed it and fitted it to the plug.....

    Now the pump works like it was supposed to.

    Im not sure how common this fault is. Diodes dont tend to blow very often. But just in case someone else has a very loud vibe pump, then this just might be the cause of the problem. Even if its an Ulka or Eaton pump, if the diode has shorted, then just adding another diode in series (eg a 1N4008 or equivalent) should fix the problem.

    BTW: the coffees actually tasting better now as well.

    Cheers,

    Mark.


  2. #2
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    Join Date
    Aug 2004
    Posts
    2,312

    Re: Loud vibe pump problem

    Mark,

    the clue to "blown diode syndrome" is usually *that the pump vibrates, but wont pump properly when the extra resistance of the puk is added to the group. It kind of looks at first, as if the grinds have choked the flow. So Im surprised the machine was able to brew coffee (in the normal sense) at all! No wonder the coffee now tastes better *:D

    Fortunately, blown diodes in this application are not really a common occurence, this being therefore a good example for the CS forum.

    Your BZ35E must be an "early/er" model. Theyve had rotary impeller pumps fitted atleast 2 years now that I know of.

    Regardz,
    FC.

  3. #3
    Senior Member
    Join Date
    Apr 2005
    Posts
    1,176

    Re: Loud vibe pump problem

    Behmor Brazen - $249 - Free Freight
    I was quite surprised that it could pump as well. But sure enough it had more than enough pressure to brew coffee. In fact it could easily hit 16 bar stall pressure. I had to lower the OPV setting to brew a ristretto at 9 bar once Id fixed the pump.... If it had failed to reach brew pressure Id have looked at it a lot sooner. Still the noise of the faulty pump nearly precipitated a divorce, so it was time to act.

    For a few months now I was getting really frustrated that the local cafe could produce a better cappuccino than I could at home (using the same beans). As soon as I fixed the pump, I was rewarded with a cappuccino of... well comparable quality. Now its time to work on technique.

    The BZ35e that both my friend and I have both use the fluid-o-tech vibe pump. Im not certain of the age but are at least 6 years old. It is set up to be plumbed in though, so Im not sure why the original purchaser decided on a vibe pump, rather thana rotary. Apparently there was an option for either pump with both versions retailing at the same pricepoint.

    regards,

    Mark.



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