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Alphason Sonata turntable running slow, please advise

Discussion in 'audio' started by harnfield, Jul 30, 2019.

  1. harnfield

    harnfield Member

    Bought off eBay for personal use,
    will go to collect this week

    Apparently it runs slowwww,
    possibly because of ageing components in the Atlas power supply? [​IMG]

    I plan to inspect for burnt components, but likely all will seem normal.

    Probably worth changing electrolytic capacitors whatever.

    I hope isn't that one of the two motors is misbehaving [​IMG]

    Have great, great respect for Mike Knowles
    defo keeping and not swapping Atlas for alternate psu !!!

    keen to hear others' experience of this issue....
     
  2. Craig B

    Craig B Re:trophile

    Have to agree with keeping these lovely classics stock.

    As the motors are standard Philips 9904 111 31813 (110V, 50Hz, 250rpm), a bad one would be the least of your worries, and would likely as not be down to motor bearing stiction, which is easily solved.

    I'd start by measuring the output voltage at T1 with the supply set to 33. According to the Alphason Sonata PCB Schematic this should be 80V (aka the sweet spot for 31813).

    WARNING: Do not attempt service of the power supply unless qualified to do so.
     
  3. cjarchez

    cjarchez pfm Member

    You could also hope for a slack belt.
    When you pick up see if the seller has the belt fitting "hooks", makes life easier.
    I saw one where a pulley was loose on one of the motor spindles...
     
  4. linnfomaniac83

    linnfomaniac83 I bet you can’t wheelie a unicycle!

    Being a dual motor design, if a motor was at fault I’d expect there to be some vibration/belt chatter due to the two motors turning at different speeds.

    It’s probably a dropped phase on the PSU.
     
  5. Dan K

    Dan K pfm Member

    I pulled one of these apart a few years back as it was humming loudly and running slow, it was an out of spec resistor. I've got the circuit diagram if you want. Absolutely fantastic turntable. Caps were all fine.

    Just seen that you've already got the PSU circuit diagram. My Alphason has the 33/45rpm internal PSU. Think it was called 'Alcalus'. I seem to remember that the resistor in question measured differently when removed from the board.
     
  6. harnfield

    harnfield Member

    Thanks a lot for your input.

    I have another Sonata which has seen better days - when I bought it, someone had glued a plastic mat on top and it was missing the puck! (Fortunately one turned up on eBay.) The Atlas looked like it had been kicked around. Then I managed to visit Mike Knowles the designer who adjusted the springs and told me that he would respray it if it were his (I forget the black he mentioned). Mike Knowles is a genius - he founded Alphason years ago and keeps his interest in audio, but his new project '3rd Way Commonwealth' aims to tackle energy poverty. (I'm not going to ask him unless essential and I get my ideas straight, he is a busy man. And I don't want to ask about the Atlas in case he doesn't knows the circuit.)

    Anyway, this 'new' Sonata uses an IEC connector for the Atlas instead of the 5 pin DIN that my 'old' Sonata has. First I plan to inspect the 'old' Sonata and retrofit the 'new' Sonata with DIN connector - which will allow me to substitute power supplies (besides being much more elegant connection, and consistent with Sonata history).

    I'm hoping that the 'old' Atlas on the 'new' Sonata will produce correct speed... then focus on whichever part has the speed issue.

    So, first will need to obtain a DIN plug & socket!
     
  7. harnfield

    harnfield Member

    Update long overdue, sorry:

    Have fitted 4 pin 240 degree DIN plug and socket to the 'new' Atlas & 'new' Sonata. Then tried both Atlas power supplies on the 'old' Sonata. Both Atlas seemed to behave the same, with the platter running between 0 to 0.3% slow - which is OK by me.

    Next, looked at how the 'new' platter turns - at a very pedestrian slow pace, yet in the correct direction!

    With the platter removed, one motor started but the other didn't - until nudged.
    Turned off and on a few times, and sometimes the "good" motor seemed to be quivering without starting.

    Would the deck itself contain any components other than the two motors? Might there be old capacitors?

    Do the motors need replacing?

    Any observations and comments would be gratefully received.


    ps:
    I used two lengths of cotton thread to pull the belt outward and outside the motor pulleys while lowering the platter, then released the cotton (two pairs of hands required). This seemed to best method I could figure out, as don't have the metal device that some mention was supplied by Alphason.

    Next time I could try ribbon (instead of thread) to avoid cutting the thin rubber belt.
     
  8. harnfield

    harnfield Member

    The bearing looks normal, in that the phosphor-bronze sphere is still glued to the tip of the bearing pin, and there is oil.
     
  9. YNWOAN

    YNWOAN 100% Analogue

    I doubt the motors will need replacing and the fact one is quivering suggests it is a power supply issue- specifically a capacitor issue. I don't know if there is a phase capacitor in the deck but have a look. I would replace any old electrolytic capacitors in the power supply too (certainly ay leaking or bulging ones).
     
  10. colasblue

    colasblue pfm Member

  11. Dan K

    Dan K pfm Member

    There was a 0.47uF Sprague orangedrop phase cap in my deck, I replaced it with 4 off 0.1uF Blue Roederstein 1% polyprops. I measured these to make sure I had exactly 0.4uF. This did gave me a decent, although slight, reduction in motor vibration.

    You may also want to look at the thrust washers/ bearings (?) on the bottom of each of the motors, the grease may have turned solid.
     
  12. Dan K

    Dan K pfm Member

    I think the 2 spheres that run against each other are actually Tungsten. These are pressed into the phosphor bronze bearing well/ shaft.
     
  13. sq225917

    sq225917 Bit of this, bit of that

    Quivering motor means one phase is down.
     
  14. Nick E

    Nick E New Member

    You sound like a knowledgeable group! Can I pick your brains please? Which oil should I use for my Alphason Sonata spindle bearing? I'd rather not trouble MK with this! Thanks in advance. Nick
     
  15. Dan K

    Dan K pfm Member

    I'll say Linn Black, although I think they originally came with a golden coloured oil.
     
  16. JimmyB

    JimmyB pfm Member

    Compressor or sewing machine oil.....nothing special
     
  17. Nick E

    Nick E New Member

    Thank you.
     
  18. YNWOAN

    YNWOAN 100% Analogue

    I wouldn’t personally recommend sewing machine oil - too thin. Compressor oil should be fine though.
     
  19. Ian Munday

    Ian Munday New Member

    Have you fixed the Speed issue on your Sonata?
    I have one with a similar issue and hope that it is not the Atlas Power Supply.
    If it is, I was wondering about getting a couple of DC motors.

    I will take another look to see if the motors both run the same and if not I may consider replacing them, although they are way overpriced for what are cheaply made basic motors.

    The Sonata With HR100MCS is my favorite deck out of all my collection (Pink Triangle Too, Avalon, 301, 401, TD124's ) and only my Focus One comes close for musical enjoyment, although it is not in the same league for detail retrieval.
    I also have a second Sonata over in Spain (I bought them cheaply together with the 401, 301, TD124's) when nobody wanted records)

    My wish would be to get a Sonata in Wood, as both mine are in black.
     
  20. harnfield

    harnfield Member

    On assumption that these motors either work or don't, and mine do appear to turn, knowing that the Atlas power supply is working, then it is down to the bearing.

    David Knowles (son of the inventor of the Sonata) informed me that speed can depend on the oil. Ordinary car motor oil was used (ie. 20W-50) and the quantity is critical. The neck of the spindle has a narrower section part-way up, and this provides a reservoir from which oil can emerge if oil is lost. It seems that friction may increase if there is either too little oil (rubbling of spindle at the side of the bearing shaft for example) or too much oil if it extends high up the shaft. I am not sure but the quantity of oil might be as little as 10 milli-litre, two tea spoonfuls.

    Looking at my spindle after wiping away the oil, it seems to have a discoloured coating of hardened oil. I expect this may be narrowing the gap, making the bearing hrder to turn. So I will use a solvent, dry the bearing, then add fresh oil....

    I will ask my local car garage for a tiny amount, as car oil is sold only in large containers.
     

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