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Thread: Oscillating brew gauge needle on VBM

  1. #1
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    Oscillating brew gauge needle on VBM

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Could any knowledgable C/Ser out there tell me why the brew pressure gauge needle oscillates so fast that it is a blur during back flushing of my VBM Levetta. This usually happens during 3rd or more back flush. I am sure it is not good for the gauge.
    Has anyone any ideas of how to recitfy this problem?
    Thanks. Herbie.

  2. #2
    Senior Member flynnaus's Avatar
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    Re: Oscillating brew gauge needle on VBM

    I never saw this happen on my Levetta. When backflushing, how long do you run the brew cycle for? If its longer than 6 seconds then maybe you are doing it too long.

    My routine was add about 1/4 tspn backflush detergent to the blind. Add small amount of hotwater to dissolve the detergent. Lock into grouphead. Lift lever until you hear the pump change tone (5 - 6 seconds. Disengage brew lever. Wait for about 20 seconds for the detergent to work then run two or three more short cycles (on for 5 seconds, wait for 5 seconds). Then I rinse the blind filter and replace it in the grouphead for cleanwater backflush - about 4 or 5 cycles running 5 seconds on, 5 seconds off.

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    Re: Oscillating brew gauge needle on VBM

    Hi Herbie with our Hydraulic gauges at work we fill the line with oil.The oil goes through the gauge and makes the needle stop vibrating

  4. #4
    TC
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    Re: Oscillating brew gauge needle on VBM

    Hi Herbie,

    It can be a sign of a sticky OPV....Might be worth checking your machine for scale and could be time to give the OPV a once over if a descale doesnt help.

    2mcm

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    Re: Oscillating brew gauge needle on VBM

    Hi flynn aus ,martybean and 2MCM,
    Sorry I have not replied before but have been very busy at work (4.45 AM start, 7.30 PM finish-no days off)
    I thought the problem had gone ,but it happened again on the 3rd backflush last night. >:(
    Machine is 17 months old and because I have always used rainwater I havnt bothered to descale, but had better pull my finger out now!!
    I havnt got any descaler, but have got some citric acid.
    I used this in my old Via Venezia and it seemed to work OK.
    What do you experts out there think of citric acid descaler?
    Thanks for all your help full advice.
    (I use 2MCMs recommended method to back flush and detergent clean )
    Herbie. :)

  6. #6
    Senior Member flynnaus's Avatar
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    Re: Oscillating brew gauge needle on VBM

    The standard advice on using citric acid for descaling higher end machines i s DONT.

    Çitric acid wont dissolve the scale but it may dislodge and relocate to somewhere that may cause even more problems. Get the proper descaler.

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    Re: Oscillating brew gauge needle on VBM

    Thanks flynn aus,
    will definitly heed your advice and get some good descaler from a sponsor pronto.

    Herbie.

  8. #8
    Senior Member GregWormald's Avatar
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    Re: Oscillating brew gauge needle on VBM

    Hi Herbie,

    Im not sure why you backflush three times in one night, or why the needle responding to the on-off cycling of the over-pressure gauge is a problem.

    How does the coffee taste?

    Greg

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    Re: Oscillating brew gauge needle on VBM

    Happy new year everone, :)
    Well ,2 months down the track and the brew pressure guage is still oscilliating as bad as ever ,despite 2 descales, detergent backwashes, and dissassembling, cleaning and relubricating the bypass valve (which was as clean as a whistle with the little red rubber piston seal looking good too).
    I am now thinking maybe the guage is faulty as the machine is working perfectly with brew pressure oscillating between 9 and 12 when brewing. :-/
    Am I right in thinking that the coil in the brew guage copper tube is meant to dampen needle vibration?
    Thanks for all your previous helpful comments C/Sers.
    Herbie

  10. #10
    Mal Dimal's Avatar
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    Re: Oscillating brew gauge needle on VBM

    Gday Herbie.... :)

    It may be that the gauges internal damping mechanism has failed mate and therefore requires replacement. Probably not a common occurrence but it does happen occasionally. Perhaps you can track down a suitable test gauge that you could connect into the same location via T-Connector and see if this replicates the oscillation? This would be the ultimate proof required, one way or the other.... 8-)

    Mal.

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    Re: Oscillating brew gauge needle on VBM

    I agree that the pressure relief valve may be in need of some maintenance. Take out the spring and piston and inspect them closely. Shine a bright light into the bore and check for corrosion, debris, etc.

    You can also pull the return line out of the reservoir and watch the flow when the gauge is oscillating. See if the water flow is in sync with the oscillating.

    I know that some Domobar Supers in the US (about three years ago or so) had the wrong spring specd for the OPV. Replacing them solved the problem. You might try that, just in case.

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    Re: Oscillating brew gauge needle on VBM

    Thanks so much Mal and Randy G for your valued advice. Just part of the wonderful comaradary from the C.S. family. Much appreciated .
    Herbie. :)

  13. #13
    Senior Member Yelta's Avatar
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    Re: Oscillating brew gauge needle on VBM

    Quote Originally Posted by 4E4354444F43260 link=1255947223/8#8 date=1262653232
    Am I right in thinking that the coil in the brew guage copper tube is meant to dampen needle vibration?
    Morning Herbie, the coil in the light weight gauge copper tubing is there to relieve stress on the tubing, helps prevent the tube from cracking due to vibration.

    Cheers,

    Jon. :)



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