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Leak Stereo 20 rebuild

Discussion in 'Tube Audio' started by vishalk, Jan 12, 2018.

  1. vishalk

    vishalk AK Subscriber Subscriber

    Messages:
    189
    Location:
    UK London
    Yup I got bitten by the valve bug, couldn't help myself bought a leak stereo 20 and had to rebuild it.


    Before Pics.




    Most of the components had to be replaced due to either drifting in value or being faulty (leaky caps) as this was going to be a daily runner I wanted it reliable so everything was changed.





    These amplifiers are such a pleasure to work on. Made sure all the resistors face the same way and that its all straight and tidy.
     
    soundmotor, drtool, Gruvin' and 3 others like this.

     

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  2. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
    2,713
    Location:
    Burlington, NJ
    Very nice job. I love the layout on these amps, very tidy and for the most part symmetrical. Looks like you found a very clean unit to start with.
    So how does it sound?

    BillWojo
     
  3. AlTinkster92

    AlTinkster92 AK Subscriber Subscriber

    Messages:
    3,242
    Location:
    NC
    Been looking at that Cary SE amp you have listed....:) Al
     
  4. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    I've been contemplating doing mine, which I've had for years. Pulled out of storage, threw some tubes in it, variacced it up , sounded like crap, one output tube running hot. Looks like simple project. I'd replaced c-1 with caps under chassis years ago. Noticed differences in r-13, 16, 31 & 34. Mine are 1 meg, Sams photofact info same. Yours appear to be 470k. Curious about running production changes on these, but hard to track since I don't think the factory used serial numbers (at least not on mine).
    Curious as to your total parts cost, not including tubes?
     
  5. vishalk

    vishalk AK Subscriber Subscriber

    Messages:
    189
    Location:
    UK London
    Hi Catmanboo, you should do it man, it wouldn't take you long at all. Yes unfortunately the caps always go leaky on these amps, and the resistors tend to drift if that happens then yes it would sound rubbish.

    As always when you replace parts you must always check the voltages around the circuit, it really is a simple project which is testament to leaks circuit designs and the ability to repair these amplifiers, hence why they will last many lifetimes.

    Do yourself a favour recommission your old amplifier back to how it should be, making beautiful music.

    There was changes made in the transformers used on these amplifiers,i forget the year, because of this changes were made to the values used on the resistors. All of this can be easily checked and found out.

    As for total parts cost, peanuts actually. Well depends what you want and if you believe all the hype on expensive audio specific components.

    For me i used http://www.farnell.com/

    I wanted to use a similar size resistors to the original, 1w resistors when these amps were built were bigger then today's 1W resistors. I used 2W resistors all round, plus the length of the leads are longer! This is important as it fits some of the long tags on the circuit board.

    I used TECONNECTIVITY (the larger resistors in the picture) CFR range.

    http://www.farnell.com/datasheets/1...k1H8b8TPU09pAUmNb49KtzLBbQxAGlHxoCpIQQAvD_BwE

    Very good resistors and i also used VISHAY PRO2 resistors.

    The russian PIO were bought from ebay (again search for good sellers and prices).

    Anyway cost me around £100 for the components (cheaper if you use Poloproplene capacitors instead of PIO)
     
    Last edited: Jan 13, 2018
  6. vishalk

    vishalk AK Subscriber Subscriber

    Messages:
    189
    Location:
    UK London

     

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  7. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    Gonna get on it soon, it's been sitting too long & my curiosity is up now! Appreciate your feedback & info, and yes, that thread is a big help. I'm gonna start checking each part individually to see what's out of order, but replacing coupling & the rest of the electrolytic caps, then voltage checks all around. I'll be using a proton 1100 preamp to feed it for ops check. Cheers, man! Hope it's warmer where you're at than it is here in n.e. ohio...:rockon:
     

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  8. soundmotor

    soundmotor super modified Subscriber

    I had an ST50 and that was my impression too. Although it had been worked on it was essentially stock w/ many original caps. I got rid of it before I did anything more and always wondered what it might have sounded like after a full rebuild. Then again, have always heard the ST20 is the best sounding of the Leak stereo amps.
     
  9. soundmotor

    soundmotor super modified Subscriber

    Where are the power supply resistors on it? Are they under the tag board? On the ST50 they came through the top.
     

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