Saturday, March 29, 2014

Minima - AUDIO Board - Work In Progress

The SMD Caps were received, and therefore layout of my Minima AUDIO and Power Board has resumed.

This initial layout still has a few problems, and it has far too many vias (32) to my liking. I can build vias using the Homebrew Toner Transfer Method, but they are not fun, or at least at the size (40x15 mil) that I want.

This board contains (left to right, top to bottom): On the top row; TxRx Relay and Control, SideTone/CW, Audo PreAmp, Main Power Connector and Regulator (a little lower). On the next row; the KEY Jack, PTT Jack and Mic Amplifier, and the Audio Amplifier and Phone Jack.

My Minima AUDIO and Power Board
Proposed Configuration
If all goes well, the board size will be as shown at 2 x 4 inch. There is still room for additions or modification, but any additions will more than likely mean more vias. :-(

The circuit is a slight modification of the original Farhan Minima Transceiver circuit, I added; the Power Supply with Headers for the other Modules, I included the KEY and PTT circuits on this board because I wanted their Jacks near the Mic and Phone Jacks on the same board. A CPU signal and its Power Header is also included.

I still have to find a suitable Large Cap (500uF - Lower Right), I think the footprint as shown will work.

I just checked, and I need to order more Toner Transfer Paper, I may not have enough to build this board, especially if I make a mistake, Dang !

UPDATE: Mar 29, 2014 12:16

With a little digging, I found a stash of nice 35V 330uF Caps in my part bins, two of which I will use to replace the single 500uF cap as per the original schematic. The caps that I found are stand-up through-hole mount. I moved the connecting traces to the back side so that they could be soldered without the need for front-side solder (underneath the cap).

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  1. I'm guessing you have considered using some through hole parts to be able to remove some vias. Or using larger SM resistors (1206 or so) to bridge some traces and yet have big enough traces to DIY etch it.

    Very cool project. I've been following all of your posts.

    Scott, KB0KFX

  2. Zesty,

    Thanks for the comment/input.

    Yes, sometimes larger SMD can help with cross circuit trace layout and therefore helps avoid vias. Due to my goal of making my projects "as small as I can", I sometimes forget to use this option.

    Within Modules, I can normally find a optimum layout (similar to that of the schematic) that avoids the dreaded crossed traces.

    In my projects, most traces (with vias) on the backside are used for; supply power, input, or output to each module. By using this strategy the integrity of the front side ground plane (copper pour) is maintained. The backside ground plane also remains simple.

    Another strategy that I used, is to arrange parts so that "ground" ends of components always point away from the center of the module (toward the ground plane). This strategy helps a lot during overall layout.