Home Forums Help/Technical Questions EHX Small Stone not phasing- can you verify my readings pls?

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  • #83576
    jackdunwoody
    Member

    Hello everyone!

    I bought an Electro Harmonix Small Stone Phase Shifter V2 from eBay in a “not working” condition. I am an intermediate solderer so thought I’d have a go at repairing it.

    Plugged in to a guitar and amp the signal passes both bypassed and not. I can hear the colour switch changing the sound when the effect isn’t bypassed. I guess the LFO is kaput but before I go ordering some CA3094 ICs I thought I’d ask someone else for a second opinion.

    To me the board looks clean with no unwanted bridges and no components look burned out – however the 33uF electro capacitor has a bit of it’s plastic wrapping chipped off – it doesn’t look like it’s leaked though. +VE on the board reads at 8.7V and I’ve only tried running it on a battery so far.

    If someone could have a check of these readings that would be really helpful! Thanks in advance!

    Pot reading of 1.2M ohms

    All phase ICs reading the same with Rate pot fully clockwise:
    Pin 1 – 0v
    Pin 2 – 1.72v
    Pin 3 – 1.79v
    Pin 4 – 0v
    Pin 5 – 8.5v
    Pin 6 – 8.5v
    Pin 7 – 0.76v
    Pin 8 – 0.17v (this pin seemed to start with a reading of 1v or so and dropped down to 0.17v where it stayed)

    LFO IC reading with Rate pot fully clockwise:
    Pin 1 – 0.71v
    Pin 2 – 4.62v
    Pin 3 – 4.77v
    Pin 4 – 0v
    Pin 5 – 0.66v
    Pin 6 – 0.17v
    Pin 7 – 8.5v
    Pin 8 – 4.77v

    LFO IC with Rate pot at noon:
    Pin 1 – 0.5v
    Pin 2 – 6.5v
    Pin 3 – 7v
    Pin 4 – 0v
    Pin 5 – 0.66v
    Pin 6 – 0v
    Pin 7 – 8.73v
    Pin 8 – 7.05v

    LFO IC with Rate pot fully counter clockwise
    Pin 1 – 0.07v
    Pin 2 – 6.8v
    Pin 3 – 7.44v
    Pin 4 – 0v
    Pin 5 – 0.52v
    Pin 6 – 0.v
    Pin 7 – 8.74v
    Pin 8 – 7.5v

    REALLY GRATEFUL IF ANYONE CAN HELP!!!!

    #120223
    ulixeddu
    Member

    Hey ciao. I’m testing from two days my small stone. And it has your same problem.
    Did you find asolution?
    Ulisse from austria

    #120224
    jackdunwoody
    Member

    Ciao!
    I did get mine fixed.
    I figured out that it was the IC which acts as the LFO. It’s the IC nearest the potentiometer. I wasn’t getting any oscillating voltages anywhere on the board so I supposed that this IC was broken. I bought a new one fr eBay for about £6 (€5) and soldered it in- it worked!
    While I was at it I installed a 3pdt switch to make it true bypass and have an LED indicator. I also performed the volume mod with a trim pot to make the effect volume louder.
    I now have an awesome phaser that suitable for live use!
    I hope you get yours sorted!

    #120248
    ulixeddu
    Member

    Cool! Can you maybe say me,Where did you check the oscillation voltage? From the pin 6 of the lfo to the pin5 of one of the other four transistor?
    Really thanksfull for the answers.

    #120249
    jackdunwoody
    Member

    Yes that sounds correct!
    BTW I used it at a gig for the first time last night and it sounded great!

    #120250
    ulixeddu
    Member

    Damn. I’m happy for yours, but i get voltages everywhere….
    What should i do????…!!!! I dont want to give it to a doctor
    Iwhat do i have to check?

    #120295
    automa1971
    Participant
    Quote:
    Ciao!
    I did get mine fixed.
    I figured out that it was the IC which acts as the LFO. It’s the IC nearest the potentiometer. I wasn’t getting any oscillating voltages anywhere on the board so I supposed that this IC was broken. I bought a new one fr eBay for about £6 (€5) and soldered it in- it worked!
    While I was at it I installed a 3pdt switch to make it true bypass and have an LED indicator. I also performed the volume mod with a trim pot to make the effect volume louder.
    I now have an awesome phaser that suitable for live use!
    I hope you get yours sorted!

    Where did you install the trimpot for more gain? I tried the volume mod on my 70s version 2 by replacing r11 and r42 with 10k and I get a dirty sound, less volume drop granted but I don’t like the sound anymore. Also do you have a diagram for the 3PDT switch install? Thx in advance…

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