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    Stereo ST-35 rebuild(new pics) and ST-70-PIO's

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    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Sat Jan 01, 2011 9:14 am

    Hello everybody.

    I am new here and since 2 months a proud owner of a ST-70 series II.
    There is only one little problem.
    The amp board is not that good anymore. Everything is fully working and the sound is very good.
    Especially with my fully restored Quad ESL 57 speakers.
    My Question is........can somebody help me to get a new or a good used one?
    I already bought some new capacitors to replace the damaged ones.
    Here are some photos of the damaged amp board and the rest of my set as it is now.

    [URL=http://img262.imageshack.us/i/img2839t.jpg/]



    [URL=http://img602.imageshack.us/i/img2840.jpg/]



    [URL=http://img694.imageshack.us/i/img2734jr.jpg/]



    [URL=http://img716.imageshack.us/i/img2811u.jpg/]

    My set now.

    A Blue Amp fully restored/modified Thorens TD 125 with SME 3009 and a EMT TSD 15. (the Shelter 501 mkII on the photo is sold)
    A double mono transformer volume control by Promitheus with in the middle a fully balanced Blue Amp model 42 phonostage.
    The Dynaco ST-70 series II with plays much better on the Quad ESL 57 speakers then my recently sold Audio Note Soro SE tube amp.(more control)
    A Marantz CD-80.

    Maybe sometime this or next year I want to buy a new kit or a restored original of the ST-70. Do you think its better then the series II ?

    Greetings from the Netherlands: symfo





    Last edited by symfo on Tue Feb 22, 2011 12:52 pm; edited 4 times in total

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by Bob Latino on Sat Jan 01, 2011 11:11 am

    Hi,

    That bad looking cap (C1) is a 68 uF @ 450 volt capacitor as is C2, the cap next to it. C3 and C4 are 100 uF @ 400 volt caps. These 4 separate caps replace the quad cap that was on the original ST-70's. Yes - It is more capacitance than on the original ST-70 but the VOLTAGE RATINGS ARE LOWER and these caps were a weak spot on the Dynaco ST-70 Series II. The original quad cap on the ST-70 was a 30, 20, 20, 20 uF cap but it was rated at 525 volts for all four sections. The caps on your amp have higher capacitance ratings. (100 + 100 + 68 + 68 = 336 uF) but lower voltage ratings.

    The circuit on the Series II was similar to the original ST-70. Some differences were that the Series II use solid state rectification, 6GH8A driver tubes instead of 7199's, LED's to set the bias and a capacitor in the input to limit bandwidth. They claimed that the bandwith was "limited to 20 Hz to 20,000 Hz" BUT personally I don't like the idea of having an extra .018 uF cap directly in the signal path. The other downside of the Series II ST-70 is that no one (to my knowlege) makes replacement boards for the Series II. If I had my choice I would always take an original ST-70 over the Series II due to the fact of greater availability of replacement parts.

    Bob

    merlot

    Posts : 22
    Join date : 2008-12-22

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by merlot on Sun Jan 02, 2011 11:35 am

    I too have a TD 125 MkII with SME 3009 that I bought in 1974. Didn't get used for a lot of years. Got a new belt, dustcover, changed the bearing oil and cartridge. Runs great. Can I ask what modifications have been made to yours? Have you done anything to the SME 3009?

    Thanks.

    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Mon Jan 31, 2011 8:13 am

    Sorry it took this long.
    Thanks for this answer Bob. I am saving money for a new kit.
    Done some work on the Series II. Sounds great.
    Some PIO's, Allen Bradley's and JJ capacitors.
    It is playing now. On the picture it not finished yet.
    And yesterday I bought a Stereo 35. My new project. Laughing
    I think it is a early one.

    [URL=http://img508.imageshack.us/i/img2882i.jpg/]

    [URL=http://img88.imageshack.us/i/img2913w.jpg/]

    [URL=http://img253.imageshack.us/i/img2906g.jpg/]

    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Fri Feb 11, 2011 11:17 am

    Beginning of restoring the ST-35

    [URL=http://img710.imageshack.us/i/img2927sx.jpg/]

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by tubes4hifi on Fri Feb 11, 2011 10:51 pm

    NICE JOB putting those PIOs and JJs in !!

    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Sun Feb 13, 2011 7:02 pm

    Thanks
    First I want to put these PIO's on the amp.

    [URL=http://img338.imageshack.us/i/img2865x.jpg/]
    Shocked Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy

    [URL=http://img602.imageshack.us/i/img2885.jpg/]

    But he is finished now and become like this.

    [URL=http://img189.imageshack.us/i/img2945z.jpg/]

    Put in a lot of Allan Bradley's resistors
    And these black pio's are the same as on top of the amp but with some rubber around it. Safer I think???

    [URL=http://img64.imageshack.us/i/img2880oe.jpg/]

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by mantha3 on Sun Feb 13, 2011 9:25 pm

    What is the make/model of those big green caps? Never seen ones that big. Are they subs for the ST-70 PIO coup. caps?


    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Mon Feb 14, 2011 4:11 am

    Very Happy
    No......a friend off mine wants to make a amp with these.
    He is the owner off a very beautiful, self made tube pre and power amp(photo will follow).
    And he is just finished a Hiraga Le Monstre with some old things. Only bought the PCB's.
    Just for fun and the sound is perfect on my Quads. Smile
    Here is a photo. Under the big silver can is the toroidal power transformer and the can is made of a old champagne cooler Razz
    But for my ST-70 series II it is a shame nobody has a new driver board. It is the only thing what is looking bad on my amp

    [URL=http://img844.imageshack.us/i/img0044kl.jpg/]


    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Tue Feb 22, 2011 7:30 am

    New PCB with WIMA's (PIO's and better resistors in the future)
    [URL=http://img259.imageshack.us/i/img2959y.jpg/]

    Chassis made like new (galvanise in English???) .
    [URL=http://img213.imageshack.us/i/img0039gd.jpg/]

    [URL=http://img140.imageshack.us/i/img0051uf.jpg/]

    [URL=http://img145.imageshack.us/i/img0054lw.jpg/]


    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by baddog1946 on Tue Feb 22, 2011 5:08 pm

    Any more info on that galvanizing technique? I have several FM-3 and amp chassis that would benefit from that treatment. Looks easy to do.

    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Fri Feb 25, 2011 4:36 pm

    The ST- 70 series II is finished.
    New diodes, caps, pio's and cleaned. Perfect with the Quad ESL 57.


    [URL=http://img64.imageshack.us/i/img3017w.jpg/]

    [URL=http://img10.imageshack.us/i/img3001cp.jpg/]

    [URL=http://img687.imageshack.us/i/img3011r.jpg/]

    [URL=http://img819.imageshack.us/i/img2998a.jpg/]

    And galvanizing is easy. But not easy to write it down for me in English.
    I will post pictures in a few days........



    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by mantha3 on Fri Feb 25, 2011 8:37 pm

    Nice work and well done.

    I like that place on the ST70 over the board. You could have made a couple extra and sold em for some profit I bet.

    Regardless, I dig it.

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by mantha3 on Fri Feb 25, 2011 8:41 pm

    "Plate" on the board I meant to say ;-)

    Thanks for sharing the progress. Makes me want to build more tube stuff!

    symfo

    Posts : 10
    Join date : 2011-01-01
    Age : 55
    Location : Netherlands

    Re: Stereo ST-35 rebuild(new pics) and ST-70-PIO's

    Post by symfo on Fri Mar 04, 2011 6:11 pm

    The first PCB is almost finished.
    Very Happy
    Never did this before and what you see costs me about 3 hours and I used only cheep resistors and normal Wima's.
    Only try to copy the original with new parts. Nothing more and nothing less. Do not now more about technics. Only copying. First project....
    First I want to try to let it play and then maybe a little bit of modifying.
    And bought me a quad of NOS Philips miniwatts. Can see them on the picture with the old Dynaco's. Are they any good ???????
    Hope to have some time this week to finish the second PCB.
    And if you see something funny, strange or wrong.......please let me know.

    [URL=http://img64.imageshack.us/i/img3090c.jpg/]

    [URL=http://img832.imageshack.us/i/img3088q.jpg/]

    [URL=http://img17.imageshack.us/i/img2985ry.jpg/]

    And if I am in trouble.......My two friends Hans, who build these beautiful amps below, and Martin are always willing to help.
    More pictures this week I hope....

    [URL=http://img819.imageshack.us/i/img157l.jpg/]

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