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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


    Dynaco st-35 95 Ohm resister got very in seconds

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    patrick279

    Posts : 2
    Join date : 2019-02-09

    Dynaco st-35  95 Ohm resister got very in seconds Empty Dynaco st-35 95 Ohm resister got very in seconds

    Post by patrick279 on Thu Jun 18, 2020 1:34 pm

    I just finished installing new driver boards from Dynaco Parts and new gold plated rca inputs; in a working St-35. After doing my safety checks I turned the amp on and put some music through the amp. I noticed within seconds that the 95 ohm smelled hot. I double checked my wiring, it was right so I searched on line for the answer, I founded the solution on an other forum. The gold plated rca inputs that I used were not grounded to the chassis like the original. I grounded the rca inputs and turned the amp back on ,now every thing is fine.
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    Mark Korda

    Posts : 43
    Join date : 2009-12-29

    Dynaco st-35  95 Ohm resister got very in seconds Empty Re: Dynaco st-35 95 Ohm resister got very in seconds

    Post by Mark Korda on Sat Jul 04, 2020 11:04 pm

    Hi Patrick, I did the same mistake you did.I didn't ground the shiny new gold jacks.I did a complete rebuild and when I did my first test Pat Boone's April Love came thru my speakers but there was nothing hooked up that was a music source.It took a ride to Frank VanAlstines to find that out.I won't mention the cost.He found out another important thing.The guy on ebay from who I bought the ST-35 had shoved some different tubes in the sockets of the power tubes.The lettering had worn and I assumed they were correct.They were not.The amp sings now and I am forever experimenting with active,passive,transformer,preamps that like the amp I rebuild myself.Everything seems to work great with that amp. Im listening to a Heathkit AA-32 tonight a 10 watt stereo tube amp with a preamp section. I'm always trying to compare that with my ST-35 and a passive preamp.In a small room like mine and adding a Parts Express Titantic 12 inch woofer using a Y cable I get my own Magico sound for pennies. Take care Pat, Mark Korda
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    patrick279

    Posts : 2
    Join date : 2019-02-09

    Dynaco st-35  95 Ohm resister got very in seconds Empty Re: Dynaco st-35 95 Ohm resister got very in seconds

    Post by patrick279 on Sun Jul 05, 2020 11:06 pm

    Mark, thanks for the reply. It was a silly mistake looking back on it. The original rca inputs were clearly mechanical grounded to the chassis, plus there is a ground from the power supply to the chassis, however, I have replaced the rca inputs on two Dynaco st-70S and a Hammond ao-58 which is pretty much a copy of a st-70. So this was my first time working on a St- 35.
    I think the st-35 is a great little amp, I had a chance to borrow an AA-32 years ago and really liked it, but I did not have a st-35 at the time to compare the two, so good for you Mark.
    I made some slight changes to my st-35 , I installed an on and off switch and added a choke to the power supply. Plus as I said above I built and installed new driver boards from Dynaco Parts. These boards are much better then the original, plus everything it labeled and all the parts are numbered. I also rebuilt the power supply and bias circuit. The amp always sound good to me. Hopefully now I now have a reliable amp for the long term. Happy listening.

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