Harmon Kardon ST-8

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I have a pristine ST-8 just pulled from storage and it seems the dreaded Hall Effect is Sensor might have gone bad.

Can anyone provide expected Voltages at the motor.

Thank You Peter

Comments

  • F1nut
    F1nut Posts: 52,294
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    You might try asking that question at AudioKarma.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • SeleniumFalcon
    SeleniumFalcon Posts: 4,358
    edited January 2024
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    The service manual is available at the vinylengine site, here is a tabulation of the voltages present at transistors:

    cn0s802px8o9.png

  • mhardy6647
    mhardy6647 Posts: 35,513
    edited January 2024
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    @SeleniumFalcon beat me to it.
    https://www.vinylengine.com/library/harman-kardon/st8.shtml

    yv20aozsuf8u.png

    EDIT: It's a really comprehensive and intelligible service manual, too! B)
  • SCompRacer
    SCompRacer Posts: 9,271
    edited January 2024
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    I repaired an ST-8 for a friend. The motor had a bad hall effect sensor. I used a motor out of a donor ST-7. In my copy and paste notes, a post from diyaudio said a Dual CS 701 or 721 might be able to donate a hall effect sensor. I have no idea if there are substitute sensors that could be used.

    It's common for the base of the cueing air pot to deteriorate and crumble. I came up with a fix in the link below. Airpot would still made them at the time though it was a pricey replacement ($97 US in 2022).

    https://forum.polkaudio.com/discussion/197116/harmon-kardon-st-8-turntable-on-the-bench
    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
  • SeleniumFalcon
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    The designer of the Hall effect motor:

    4m75q5z3ez1v.png
  • mhardy6647
    mhardy6647 Posts: 35,513
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    very effective.