[sdiy] My SMT projects

[mark verbos]

Why are there so many electrolytics on those boards? Is that because you 
have so many bypasses?

I've been staring at this thing wondering that.

mark

Tony Clark wrote:

>   Since the discussion of surface mount technology cropped up, I thought 
>I would share what I've been doing with it.  My idea was to make compact 
>modules that had every feature I could think of built right in.  Somewhat 
>inspired by Grant's fabulous work with the Wiard modules:  Lots of 
>functionality in a small package.
>   The first module, M101A is a classic VCO module, built around a 
>modified ASM-1 core.
>  
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m101a_01.jpg
>
>   The VCO has 9 waveform outputs:  Sine, Triangle, Tangent, Sawtooth, 
>Square, Pulse, double frequency (2x) Triangle, 2x Saw, 2x Square, and 2x 
>Pulse.
>   I ended up with this many different waveforms due in part to the 
>waveshaper circuitry I used to get the sine waveform.  I find it 
>different since it isn't necessary anymore to use two VCO's tuned one 
>octave apart!
>
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m101a_02.jpg
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m101a_03.jpg
>
>   These images show a mostly completed PCB for the VCO.  I had run out 
>of electrolytics at the time, so the bottom 2/3rds wasn't finished at the 
>time of the photograph.  The top 1/3 of the PCB contains the VCO core, 
>the other circuitry are the waveshapers.
>   As this was the first of these modules, I did some things differently 
>than I do them now.  I put all of the resistors on the bottom side of the 
>board.  If I were to do it now, I would put as much as I could on one 
>side and only resort to putting components on the bottom side if space 
>became an issue.
>   PCB statistics:  249 components, 588 connections
>
>   The second module I did was a VCA board:
>
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m201a_01.jpg
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m201b_01.jpg
>
>   I used one PCB to make two distinct modules.  M201A is a quad VCA 
>while M201B is a dual VCA with main outputs and soft-start circuitry to 
>eliminating thumping on power-on.
>
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m201a_02.jpg
>http://www.physicsenterprises.andrews.edu/~clark/diy/images/m201b_02.jpg
>
>   In the above PCB pics, you can see that M101A uses the top-half of the 
>PCB, while the lower-half is used for M101B.  On this board I was able to 
>put all of the components on one side.
>   PCB statistics: 307 components, 588 connections
>
>   I have one more module, M301, which is a variation on the Moog ladder 
>filter (variable pole) plus an onboard ring modulator.  I don't have any 
>pictures of it up currently, but I may be able to add it in the next day 
>or two.  It is the most complex board I have done to date with over 318 
>parts and 685 connections!  For that board I did have to utilize the 
>backside to put a few parts, but I limited it to the large 1210/1206 
>resistors.
>
>   All of the PCB's use 10mil traces with 10mil separation.  I think the 
>latest board uses 8mil traces with 10mil separation.  I'm really pushing 
>the limits of the PCB house that I get my boards from.  They guarantee 
>8mil/8mil, and although their boards have been great, I did have a 
>bridge that occurred on one board.
>   Building boards this complex hasn't been without it's problems.  All 
>of the boards have had at least a couple of errors (mainly due to 
>schematic entry snafus), so I learn something new each time.
>
>   Some other things of interest:  The boards are all completely CV or 
>GATE controlled.  That made it more of a challenge, but more rewarding as 
>literally everything can be modulated!
>   The connectors are VME 96-pin and are great!  I like the fact that 
>since the PCB isn't physically wired to the front panel, I can unplug the 
>PCB and put in another one (if one should ever fail) without any hassle.
>   The front panels are custom punched 1/8" anodizing grade aluminum with 
>engraved legending.  The letters are hand-painted and then the whole 
>panel is finished with a clear matte lacquer.  
>   My first panels were hand lettered and finished with a hard 
>polyurethane.  But it was extremely time consuming and frustrating.  In 
>the end that kept me from making any more modules until I had found an 
>adequate solution to my panel making problem!  I'm pretty happy now 
>about the way they look although the lacquer is a bit fragile.  I need a 
>good alternative that's more durable.  If anyone has a suggestion, let 
>me know!
>
>   Well that's about it for now! BTW, anyone who would like to see my 
>modules in person should attend the AHMW show on April 6th.  I plan to 
>bring them along with my Modcan and Fenix (plus something special...)  
>   Details can be found here:
>
>   http://www.ph.k12.in.us/~drew/ahmw2002.html
>
>   Cheers,
>
>   Tony
>
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>"We wouldn't want to ship something that doesn't work"
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>     Excerpt from EE Times April 2, 2001
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