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    Started my first ST-70

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    Dallas

    Posts : 18
    Join date : 2015-04-16
    Location : Denver

    Started my first ST-70

    Post by Dallas on Sun May 24, 2015 10:51 pm

    So, with most of final version fleshed out, it was time to prepare the chassis, power coat and blast, and polish the coppercap and the quad cap. Then I ceramic clear-coated the exposed metals.
    Next to get done is wiring the chassis, building the board, and final assembly. After that, I'll finish the integrated chassis design that this will drop-fit into. Jumpers will run out for biasing, volume control, power, source select (including y2 DAC from AMB labs.)

    One stage at a time. Back to work.

    (That photo makes the copper cap look way more scratched than in reality. That thing is an orange mirror.)
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    Bob Latino
    Admin

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

    Re: Started my first ST-70

    Post by Bob Latino on Wed May 27, 2015 7:20 pm

    Hi Dallas,

    I am going to move your thread over to the Basket of the Forum where it will get more views .. Could you explain in more detail to the forum members how you got that unique finish on the chassis and transformers ? I have never seen a finish on a tube amp quite like what you have on your amp .. That is really nice looking ...

    Bob

    Dallas

    Posts : 18
    Join date : 2015-04-16
    Location : Denver

    Re: Started my first ST-70

    Post by Dallas on Thu May 28, 2015 10:43 am

    I used a powder coat called Silver Vein.

    [EDIT: I baked it at about 400F for half an hour then sandblasted the surface. The coating needs something to stick to. Then I blew it all off and wiped it down with a surface prep solution before powder coating. Then it got baked again and left to cool.]

    After scrubbing, it came out looking like pitted iron. I have another one that will show copper instead of silver. I may have been happier with that when building the final cabinet - being wood and all -, but this is a first run anyway. I'm having fun.
    For the transformers, I sanded then brushed off the black paint to base iron, cleaned and varnished in a high-temperature clear coat. I used the same stuff on the quad-cap and copper cap after I polished those up.

    (I must have wiped my finger across that copper cap while photographing.)


    Last edited by Dallas on Thu May 28, 2015 11:17 am; edited 1 time in total (Reason for editing : More detail added - powder coating is easy if you've got an oven, sand blaster, spray guns, racks, barrels of coating... Yeah, cheaper to go to a body shop.)

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Started my first ST-70

    Post by sKiZo on Thu May 28, 2015 5:26 pm

    Nice attention to detail ... cleaning all the leftover gunk off the plates is a lot of work, but pays off in the end.

    Nudie pic!


    Dallas

    Posts : 18
    Join date : 2015-04-16
    Location : Denver

    Re: Started my first ST-70

    Post by Dallas on Thu May 28, 2015 10:34 pm

    Thanks sKiZo!
    Yeah, it was a pain. I have a number of wire brushes that worked best for me before finishing up with ScotchBrite.
    However, now that I have done this once, I could make a quicker go of it. I had considered offering to coat anyone's chassis before mailing it back but it would be cheaper to visit your local powder coat shop: $75-$100 per chassis including bolts.


    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Started my first ST-70

    Post by sKiZo on Thu May 28, 2015 10:50 pm

    Chrome plating, anyone?



    I decided against it ... too gaudy, even for me ... clown

    Dallas

    Posts : 18
    Join date : 2015-04-16
    Location : Denver

    Re: Started my first ST-70

    Post by Dallas on Wed Jul 08, 2015 7:00 pm

    Okay, first hot run and the sound is wonderful. I am running McIntosh ML-1Cs (w/ MQ-101) and the sound is, well, most here already know.

    The wiring harness hanging out is a way to insert a DC mA meter (0-75mA Simpson) and selector switch (2P5P BBM 4-deck rotary) for the bias circuit to be monitored. It has an "off" bypass circuit, too. These will be installed in a slightly larger chassis... that I have yet to cut and fold. This will also hold the the VU meter, source select, and a big fat toggle master on/off.

    The annunciator light is an old salvage and is mounted over two LEDs from the time-delay board: flashing red for warm-up and solid amber for run.  

    Other than that, it does its job.
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    Last edited by Dallas on Wed Jul 08, 2015 10:06 pm; edited 1 time in total (Reason for editing : Added photo)

    bluemeanies

    Posts : 120
    Join date : 2015-02-09
    Age : 66
    Location : Folsom Pa.

    Re: Started my first ST-70

    Post by bluemeanies on Sat Jul 18, 2015 8:36 am

    Great job with the chassis!

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