Thursday, November 20, 2014

The Transistor Islands

Update: See my post with details on how to make your own island pad cutting device.

Hello. Yesterday I found myself needing to build a simple Colpitts oscillator, when I discovered a technique for making 'transistor islands', for lack of a better term. I've tried prototyping using different methods but predominately built using 'ugly style' with dead bugging. I didn't like gluing pads or using high value resistor stand offs though. Eventually I developed the desire/need for more rigid mounting of components so I opted to find a method akin to making islands. Not wanting (or being able to) spend any money on fancy island pad cutting bits, I made some of my own tools to do the job.

I had these wooden handled tools that I must have picked up a decade ago and I'm not even certain what they are used for, but I believe they can be purchased from a hobby store. I used my dremel to reshape the blades of the tools and I use these to make islands. This method was developed based on others I've seen that modify a drill bit to achieve a similar result. The tool is then used to form isolated pads, or "islands", on copper clad board and your components are mounted on these pads. The tool is held in one hand, one point is pressed down and the other point is rotated around in a circuit, cutting into the copper and forming an isolated island.

All of my "island cutters" created pads that where a little larger than what I wanted for this project, so I found that by using a sharp box cutter/utility knife blade (seen wrapped in tape for an ease of use) and cutting sections in the pad, made for a perfect little "Transistor Island". This may seem like an obvious thing to do, but if it wasn't for the many pictures of different circuit building styles online, I wouldn't have figured out how to do it myself. So I share these with you.

Always wear safety glasses and a respirator mask when cutting into copper clad material. The resultant powder can be very dangerous.

The "island cutter" and box cutter used to make the "Transistor Island"
The pads are tinned with solder.

 The transistor is mounted, observing the pinout, continuity must be checked throughout the entire build process to prevent any shorts.

The completed Colpitts oscillator, with crystal socket. The 100ohm resistor with flying lead is for power and the disc ceramic the output.

The final circuit with crystal mounted. 

I should note that this method is time consuming and doesn't lend itself to easy modifications, so it is best for proven designs, rather than experimentation (which ugly style is better suited for). This is a bit more crowded than I would generally like my circuits to be, but this was also the first time I was experimenting with this idea. 

Thank you for taking time to read this. I build ugly circuits and I am proud of that. I would rather build ugly circuits than to not melt solder at all.  What methods do you use? Are you a Manhattan fan? How about veroboard / stripboard? Or do your builds look like those found on the late Jim William's desk?

The workdesk of the late great Jim Williams

Thanks again & 73 from FreestateQRP.