Monday, October 19, 2009

TinyTrak: The Ugly Mod

When I say ugly, I mean ugly. I'm even embarrassed to post pics. Ok, so here's the problem. Once again I faced the challenge of dual-use. At the moment I have my eTrex Legend feeding the TinyTrak. However, rather than continuing to eat up AA batteries I want to replace it with a standard 5V hockey-puck GPS. However, I want to retain the ability to use the Legend or even my 60CSx. My fear is that if I did a solder blob at J7 that feeding 5V to the GPS might smoke it if it's not expecting it. I haven't looked at the Garmin pin-outs to see if they can take 5V on pin 4. What to do?

Well, ingenuity struck again and I decided to solder a common dual-pin jumper to the pads so I could add the jumper when I needed to have 5V powering the GPS or remove it otherwise. Unfortunately the solder pads are very close together. Oh well, no worries with my expert soldering skills. I quickly knocked the mod out, tested it, and went to put the case back on. That's when I realized my fatal design flaw. The pins were too tall and the case didn't fit. That's when I caused my real fatal error. While trying to jimmy the jumper block I popped it off when one of the solder pads came free. Crap! Let's say the wife had to come out to see what was going on.

I tried in vain to do a repair. I pulled out the magnifying lamp and a fine Xacto knife and started scraping away at the trace for the pad I pulled. That's when I realized it's a very short trace and only went to the pin on the IC. Brilliance struck again when I figured I could just make an ugly fix with a wire jumper. I took a piece of wire lead from a resistor and solder that first to the good pad and then to the jumper block. My does this look like the worst repair I've ever done but it works. It may be ugly but I still have 5V when jumpered.

I doubt I'll go back to clean it up later. I figure I'll use it like this until I smoke it (and hopefully not anything else) before I do it right. Of course I'm not sure what "right" is going to be now.

This is the ugliness jumpered for 5V to the GPS.

See? I'm not lying. :-)

And here it is unjumpered for no voltage on pin 4

And finally, wrapped up in the case (which now closes properly again)...

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