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    Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

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    maninmac771

    Posts: 28
    Join date: 2011-03-07

    Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

    Post by maninmac771 on Tue Mar 08, 2011 7:08 pm

    Hi. I'm new to this forum and hope to get some help to do some minor upgrades to my ST70.
    Firstly, I'd like to replace the old screw-type speaker terminal connector with 5-way binding posts (as shown in picture A) for use of 8-ohm speaker. I plan to go about doing this by (a)de-soldering all the wires (wires 1 to 6 as shown in picture B) from the back of the connector, (ii)solder wires 1 & 2 (from amp's chasis and transformer's common) to tip of black binding post, (iii)solder wire 4 (the 8-ohm wire from transformer) to tip of red binding post, (iv)re-join wires 5 & 6 (I've been told that the 2 wires need to be joined to form a negative return to the circuit), and (v)cover the exposed leads of wires 3 and 5/6 with electrical tape to prevent touching of the chasis accidentally. Are these the right way to do?
    Secondly, I'd like to know whether replacing the present 2-core thin power cord would improve sonic performance of the amp. If it does, can I replace it with a 3-core cable and hence is the connection going to be black wire to fuse ('b' in picture C), white wire to on/off switch ('a' in picture C), and green wire to chasis?
    Thirdly, is there any good to re-wire all internal wiring with single-core of copper or silver wires? and what gauge of wire is suitable?
    Thanks for any advice.
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    j beede

    Posts: 222
    Join date: 2011-02-07
    Location: California

    Re: Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

    Post by j beede on Tue Mar 08, 2011 10:00 pm

    Good questions. I prefer to leave the speaker terminal strip intact and use adapters like the one I built--see it pictured below. Some people report ground loop hum problems after converting to 3-wire cords (myself included). Why do you want to rewire your amp? If you choose to use silver wire you should probably use silver solder too. Have you already replaced your slenium stack and inserted forward diodes in front of your rectifier? How old is your quad cap? You might consider replacing that "time bomb" with an under chassis cap board--something like the Stokes SDS board.
    ...j

    Sal

    Posts: 217
    Join date: 2009-02-05
    Location: Central New Jersey Dynaco-ST70.com

    Re: Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

    Post by Sal on Wed Mar 09, 2011 3:45 am

    You are correct with the speaker terminal wiring. I would purchase a dual binding post speaker terminal kit from Dynakitparts.com as the outcome will look more professional. You will receive a phenolic board, dual binding post, terminal strip and screws. Much better than using electric tape on wires.

    You can install a 3 wire line cord but be aware you might encounter a ground loop hum, depending on your input source.

    I have no opinion on silver wire. I would leave well enough alone.

    Sal

    maninmac
    Guest

    Re: Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

    Post by maninmac on Wed Mar 09, 2011 1:40 pm

    Thanks Sal. I'd think about getting the kit from Dynakitparts instead of a diy job and take note of the possible ground loop hum following a 3-wire line cord replacement. As for re-wiring, this is in fact not of priority. Rather, I agree with j beede's suggestion about replacement of quad cap and rectifier. By the way, his self-built adapter certainly looks cool. I was wondering what that red plastic part of the adapter could be?

    Luddite

    Posts: 234
    Join date: 2009-02-04
    Age: 63
    Location: Texas

    Re: Dynaco ST70 - upgrade speaker terminal connector, power cord & internal wiring

    Post by Luddite on Wed Mar 09, 2011 4:17 pm

    maninmac wrote:Thanks Sal. I'd think about getting the kit from Dynakitparts instead of a diy job and take note of the possible ground loop hum following a 3-wire line cord replacement. As for re-wiring, this is in fact not of priority. Rather, I agree with j beede's suggestion about replacement of quad cap and rectifier. By the way, his self-built adapter certainly looks cool. I was wondering what that red plastic part of the adapter could be?


    Looks like a banana jack.

    Charlie

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