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What’s knocking on my AR ‘The Turntable’

Discussion in 'classic' started by 766fmj, Oct 30, 2017.

  1. 766fmj

    766fmj New Member

    Hi all,
    So, I’ve got my AR ‘The Turntable’ and I’m very pleased with the overall condition and it’s operation.
    I’ve given it a good clean out of any dirt and grime. It was extremely clean as it’s seen low hours then stored away. I haven’t yet got in to oiling as I need to get some sewing machine oil tomorrow. I’ve got a new turntable belt on as well.
    I have one question for everyone if I may.
    When playing on 33RPM there is a knocking sound.
    There is no knocking sound on 45RPM.
    Can anyone enlighten me as to what to do?
  2. killie99

    killie99 pfm Member

    Have you got oil in the bearing? If not DO NOT RUN THE TURNTABLE!!!!!!

    Can you tell where the knocking noise is coming from?
    Does it knock with the outer platter removed?
    Does it knock with the outer platter inverted (ie turned upside down but still sitting on the inner platter)?
  3. Mignun

    Mignun pfm Member

    As Killie says above, don't run it without oil. First make sure the bearing is OK and all there - I can't recall whether the AR Turntable runs with a captive ball, but if this is missing then you need to replace it.

    Then invert the outer platter and then see whether anything is amiss. It may be that something is out of alignment, or the is belt riding the pulley or inner platter or it could be the motor needs attention or replacement.
  4. cre009

    cre009 Member

  5. stevec67

    stevec67 pfm Member

    Posted this yesterday but it got lost in the server wobble. Itn is almost certainly the motor thrust washer or spring. The motor spindle rattles up and down under drive and knocks like this. Sometimes you have to add a thrust spring, other times(LP12 owners take note) you remove the thrust spring and it stops.

    Test for this with the belt removed. See if it still knocks with a finger lightly pushing the spindle inwards.
  6. flatpopely

    flatpopely Prog Rock/Moderator

    My Dad has one and it knocked, proved to be the pulley loose on the motor shaft.

    Bit of nail varnish solved it.
  7. Craig B

    Craig B Re:trophile

    If the platter is knocking on the pulley once per revolution then it will likely be down to suspension sag/listing causing precession, or more specifically, a change in the first Euler angle, which will be reduced at the higher 45rpm. The solution, in this case, is to accurately level the plinth and then re-level the platter via the adjustment nuts beneath each spring from below.

    Last edited: Nov 11, 2017
  8. Dark Energy

    Dark Energy pfm Member

    What do you mean "sewing machine oil"? If you're talking about 3 in one or similar don't do it! Use the correct oil.
  9. Craig B

    Craig B Re:trophile

    Agreed, Singer oil is great for motor bearings but too light for the platter bearing. After decades of conferring with the lubrication boffins at the likes of Imperial Oil/Exxon Mobil (long standing clients of mine) I've come to the conclusion that Rega have been right all along; a few drops of 90wt gear oil is the way to go, applied by letting the drops run down one side of the clean bearing well from the top before putting a drop on the ball bearing and plopping it in. As the oil is down one side only, the sub-platter spindle will easily slide straight in (without turning) letting the air escape; then simply spin the sub-platter by hand to distribute the oil and never disturb it again for the next decade or two.

    Note that this isn't necessarily the best for the likes of Linn bearings where the upper and lower polymer sleeves create a greater capacity oil 'sump'. Also, the earliest Linn bearing sleeves can swell if the appropriate oil isn't used (i.e. not the 'Black' oil).

  10. cre009

    cre009 Member

    The manual for this deck specifies No10 machine oil with lubrication applied annually. Many of the AR decks specify light oils without additives.
    Last edited: Nov 21, 2017
  11. Craig B

    Craig B Re:trophile

    And that is one of the reasons why 80/90w gear oil is superior; specifically, it won't run down the bearing shaft leaving the spindle dry along its length. It also won't break down under pressure as easily as lighter oils, however, this shouldn't be as much of an issue with The AR Turntable as it has a Delrin bearing thrust pad.
  12. 766fmj

    766fmj New Member

    Hi everyone!
    Many thanks for all of your help and useful comments on my issue with my AR Turntable. The sewing machine oil was recommended for the motor spindle.
    I also used a 80/90 year oil for the bearing shaft. So I believe I have done all of the procedures correctly.
    It seems that stevec67 is spot on. The motor spindle was the cause. It moves up and down but so minutely it was almost not detected. Because of the change of speed via change of belt height on the pulley - the higher up on the pulley - the more it knocked. The longer it was run the more it eventually knocked. Then mysteriously disappeared then came back after about five minutes.

    So, after much searching, I’ve found the company who would send me a replacement ‘like for like’ motor. As I am located in the UK this was a real big issue as nobody would send this to me in the UK.
    Hurst themeselves, would not export the motor. After communicating with a few suppliers I eventually found one that would place the order with Hurst and then send on to me.
    As it was a real bind to locate and buy, I ended up ordering two Hurst motors to be sent to the UK.
    3001-001 - 115v - 3w - 60Mz - 300RPM - $67.07 each plus $25 Shipping to the UK.
    My Turntable operates on 220v/240v but inside has a capacitor that reduces the current and has an appropriately sized pulley fitted.
    You just cannot get these motors anywhere other than Hurst and a few of their associated connections in the USA.
    I know there are other replacements available but at $250 each was too steep for me.
    There is another Hurst motor model I was thinking of which gave greater torque but after investigating on forums this motor was often humming once fitted so I kept it Stock.
    The motors are on the way to me now and I’ll post again once installed to give everyone an update.
    Once again, thank you to all who posted and helped out.
    stevec67 likes this.
  13. Craig B

    Craig B Re:trophile

    As with the Premotec/Airpax/Philips sleeve bearing models, there exists a small amount of vertical play in the motor spindle/rotator of the Hurst 3001-001 motor by design. The difference being that, with the exposed bottom end of the spindle on the Philips chassis, one can employ a motor thrust bearing to control the play. Regardless, chances are that your new motors will run trouble free for many years.
  14. stevec67

    stevec67 pfm Member

    Great news!

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