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Rebuilding Michaelson&Austin M100 -schematic needed

Discussion in 'classic' started by finkaudio, Sep 17, 2018.

  1. Anthony Gibbs

    Anthony Gibbs New Member

    Hi, I'm a new member here and have been surching for help with my Papworth Burgundy TVA-8 stereo amp, one of my output trannies has gone low resistance, I need a new one and need to try to match it with the other, I have emailed Eddie but suspect it's an old email on the Papworth site, any help or assistance would fantastic, ideally a schematic and need to know if there are any new old stock or where the original transistors were sourced, many thanks Tony
     
  2. Mullardman

    Mullardman Moderately extreme...

    Hi Anthony and welcome.
    I've not worked with Eddy for many years and TVA-8 came after my time, but I just tried to call him, as we've kept intermittent contact. Unfortunately his number came up 'Not recognised'.
    I will try a few other possibilities and get back to you.
     
  3. Anthony Gibbs

    Anthony Gibbs New Member

    Thank you, really appreciate your time, if all else fails and I have to buy an off the shelf el34 25w transistor, I assume I'll need two, also would I need to change any components?
     
  4. Arkless Electronics

    Arkless Electronics Trade: Arkless

    Erm I think you mean "transformer"! If like any of the other TdP designed Papworth amps the OPT (output transformer) is anything but standard and you will not be able to obtain any suitable replacements.

    What makes you sure that the OPT is faulty?
     
  5. Mullardman

    Mullardman Moderately extreme...

    Eddy Fincham designed the TVA-8 as a single ended pure class A amp. As such it differs from other (Tim DcPVC designed) Papworth products which are all push pull as far as I know. All of the Papworth production of original M&A TDePVC models has improved build quality.
     
  6. Arkless Electronics

    Arkless Electronics Trade: Arkless

    As it happens I just looked this up about 20 mins ago Mull! 15WPC single ended yep... It says Walrus Systems were the UK distributors so maybe they have some spares... or maybe long defunct...
     
  7. Mullardman

    Mullardman Moderately extreme...

    Sadly it looks like Walrus have gone. I visited a couple of times. Nice shop. Les Wong IIRC.
     
  8. Anthony Gibbs

    Anthony Gibbs New Member

    Yes sorry transformer, it’s a stereo amp, with I believe push pull type transformers, 6 wires 3 for 0 4 and 8ohms and 3 wires centre taped for the plates, the left channel was thin tested against the right one of the centre to valve is 20ohms almost half the other and across both valve taps measures 41ohms compared to the rights 73ohms, can I replace both with a 20w pp one
     
  9. Mullardman

    Mullardman Moderately extreme...

    I have managed to contact Eddy, but not had a conversation yet. Anthony, you have a PM.

    For the benefit of all, I should state that my electronics knowledge is minimal. My association with Papworth was more sales/distribution based. So, whilst familiar with the history and product range, I am next to useless on the technical front.
     
  10. Mullardman

    Mullardman Moderately extreme...

    P.S. I should think that if you can't get a transformer from 'stock', you could get it re-wound, especially if you can find out who made it. Have no idea what that might cost though.
     

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