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Thread: My go at externalizing the PSU, using an SPDT switch

  1. #1
    Join Date: Jan 2016

    Location: Hilversum, Netherlands

    Posts: 31
    I'm Michiel.

    Default My go at externalizing the PSU, using an SPDT switch

    Here's my story about externalizing the transformer and PSU of my SL1210mk2.

    First of all, I'd like to give the credits to Francois who inspired me to give this project a go with his excellent tutorial: http://theartofsound.net/forum/showt...chnics-SL-1200

    I decided to do the same thing, with the exception of connecting the umbilical to the PSU via a 3 point DIN connector and adding a fused (250V, 2A) IEC power inlet with a switch, so I could turn the power on and off. For me, the logical place to add the switch was right after the power inlet, so I could cut the power from the transformer. Also I used shielded cables for the umbilical and a DIY power cable. I connected the shielding of the umbilical on one end to the casing of the transformer and on the other end to the main earth point of the 1210, abduct possible EMI signals properly.

    All went relatively smooth and once I was done I gave it a go right away. The 1210 powered up very nicely and everything seemed to be working properly. Seemed? Yes! Because, when I turned on my amplifier and then the 1210 I heard a very nasty, sharp sounding pop coming out of my speakers. Even with the volume down this remained every time I would turn the 1210 on or off. Only when I turned off the speakers, the popping would disappear.

    So I did a little research to find out what could cause this problem. The answer was (of course): it was caused by EMI induced by switching off an inductive load. The solution to this would be to use a snubber network. Then I asked myself: if this problem didn't occur with the PSU inside the turntable, why is it occurring now? So I went to have a look at the schematics, and there it was: the snubber network is actually there in the PSU. However, by joining the 'thick blue and thick brown' cables and thus shorting the PSU, this snubber network is bypassed!

    So what I did is replace the switch with a 3 point SPDT type (as is used in the original design) and use the blue, brown and red (which is light blue in my case) cables to connect it. Thus placing the switch between the snubber network and the transformer, instead of right after the power inlet and bypassing the snubber network. Luckily didn't desolder the light blue yet, so the swap was made quite easily. Also, the new switch was a drop-in replacement for the old switch, so I didn't need to modify my ABS casing again.

    And lo and behold....it worked! The popping is gone and everything is working as it should.

    Hope this is of some help to you out there who might be experiencing the same problem.

    Some pics of how it turned out:

    Transformer and PSU inside the ABS casing:


    Power inlet, SPDT switch and DIN connector:


    Done:


    Inside the 1210, the shielded umbilical is a kind of rigid cable so I used several tyraps attached to the original screws as pull relief:


    Umbilical connected to the two AC poles and the shielding to the earth point:


    She powers up nicely....


    ...and spinning vinyl again! The PSU is located inside the cupboard where I can reach it easily from behind:
    Turntable Technics SL-1210mk2, Origin Live modified OL1 tonearm, Van Den Hul rewire, LDA/MCRU Step 2 PSU, Ianmac bearing, Isonoes, Achromat, Clearaudio Twister
    Cartridge Audio Technica AT33PTG II
    Tape Technics RS-AZ6
    SACD Sony SCD-XB790QS
    Ampification Accuphase E-205
    Speakers Dali Ikon 6 Special Edition
    Sub REL Strata II
    Cables Van Den Hul: MCS-150M and D-502 Hybrid (Tonearm), Integration Hybrid (SACD, Tape), CS-122 Hybrid (Speakers), The Second (currently unused). Canare: 4S8 (Sub)

  2. #2
    Join Date: Nov 2008

    Location: North Down /Northern Ireland/ UK

    Posts: 19,484
    I'm Neil.

    Default

    Nicely done
    Regards Neil

  3. #3
    Join Date: Jan 2016

    Location: Hilversum, Netherlands

    Posts: 31
    I'm Michiel.

    Default

    Thanks Neil!
    Turntable Technics SL-1210mk2, Origin Live modified OL1 tonearm, Van Den Hul rewire, LDA/MCRU Step 2 PSU, Ianmac bearing, Isonoes, Achromat, Clearaudio Twister
    Cartridge Audio Technica AT33PTG II
    Tape Technics RS-AZ6
    SACD Sony SCD-XB790QS
    Ampification Accuphase E-205
    Speakers Dali Ikon 6 Special Edition
    Sub REL Strata II
    Cables Van Den Hul: MCS-150M and D-502 Hybrid (Tonearm), Integration Hybrid (SACD, Tape), CS-122 Hybrid (Speakers), The Second (currently unused). Canare: 4S8 (Sub)

  4. #4
    Join Date: Sep 2015

    Location: Central PA, USA

    Posts: 31
    I'm Eric.

    Default

    Hi Michiel - Nice documentation of a problem AND its solution. Thanks for sharing. I created an external DC power supply for my SL1200 a while ago and removed all of the original power supply components from the PCB. Each mod makes a nice improvement

  5. #5
    Join Date: Jan 2016

    Location: Hilversum, Netherlands

    Posts: 31
    I'm Michiel.

    Default

    Thank you Eric. Maybe some day I'll try to make a decent DC PSU like you did and improve the regulator inside the deck as well. Should make a nice improvement indeed! But for that I'll have to dig up and expand my knowledge in electronics first. Has been a long time since I drew my last schematics
    Turntable Technics SL-1210mk2, Origin Live modified OL1 tonearm, Van Den Hul rewire, LDA/MCRU Step 2 PSU, Ianmac bearing, Isonoes, Achromat, Clearaudio Twister
    Cartridge Audio Technica AT33PTG II
    Tape Technics RS-AZ6
    SACD Sony SCD-XB790QS
    Ampification Accuphase E-205
    Speakers Dali Ikon 6 Special Edition
    Sub REL Strata II
    Cables Van Den Hul: MCS-150M and D-502 Hybrid (Tonearm), Integration Hybrid (SACD, Tape), CS-122 Hybrid (Speakers), The Second (currently unused). Canare: 4S8 (Sub)

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