Repairing a wireless keyboard

Last night, I sat down to use my home theater (a PC connected to a DLP projector) and had some problems typing in the name of a movie into Netflix. I thought I had mistyped the word, but I soon realized that my wireless keyboard had some non-functional keys on it. The letter 't', numbers 1 and 3 among other keys were not working. Since the failure affected more than one key, and pressing harder did not help the situation, I reasoned the problem was one of the matrix lines in the keyboard's circuit and not a bad connection in the button itself. The rest of the keys worked fine, so the microprocessor and transmitter were probably OK.

I took the keyboard apart and located the matrix lines between the microprocessor and the array of buttons. I used an oscilloscope to see which lines were pulsed (outgoing from the microprocessor) and which were switched (incoming to the microprocessor). I also compared the signals from the working "2" key to the broken "1" key. The signal was present but weak for "1". I tested the total circuit resistance for "1" and "2". "2" (working) was a couple hundred ohms, but "1" was 10k ohms. The circuit had a bad connection somewhere.
I used my meter to trace the bad connection to this spot on the flexible circuit board beneath the keys. It looks fine visually, but there is an electrical discontinuity right in the very center of this photo where the trace becomes narrow and passes above the middle rectangular cutout.

I used some conductive paint (marketed for repairing automotive defrost grids) to cover the bad area of the trace.

I was tempted to use conductive epoxy for the repair, but it can be very brittle and has low adhesion qualities. We'll see how the defroster repair product holds up.

Woodworking with a piece of raw tree trunk

My friend recently had a tree die and fall over on his property. He cut it up with a chainsaw, and offered a few of the pieces to me for use in woodworking. I have never started a project with just a raw log, so I figured it would be a fun learning experience. The tree died in the winter, and it was soaked with rain water, so I put the pieces on a few bricks to keep it off the ground and covered it with plastic on rainy days, leaving it uncovered on dry days. After the rainy season was over, I removed the plastic, and left it sitting in the sun for few months. It's dry now, but badly cracked. I have a feeling it may have been cracked even before the tree even fell over, but I would be interested in hearing from anyone who has experience drying logs.

I chose one of the smaller logs and sliced off a piece with the bandsaw.


Next, I clamped a 4x4 to the bandsaw table to act as a crude fence. It's set to a little over 1" of thickness from the blade.

I jointed the exposed log face before cutting each 1" slice with the bandsaw. I then jointed the other side of each board, and also jointed one edge. I then planed each board to exactly 1" and used a table saw to square up the other side. I now have flat, square stock ready for the project. The wood had lots of cracks, but the figure was really pretty. I think this was an almond tree.


I ended up cutting the boards into 1"x1" x 12" long strips. I decided to make a napkin holder, since it was something that I could build with a small amount of wood, and would be useful. I used standard yellow wood glue and only used tape while drying -- no clamps.


I used a 1/8" radius round-over bit in my router table to smooth the edges, then sanded with 150 grit on a random orbital sander, and also did some hand sanding. I applied a Tung oil finish (my favorite finish) in a few heavily-rubbed coats.

Improving guitar cable connections

This weekend, my band played a gig on Saturday and Sunday in Monterey. On the third-to-last song on Sunday, I started to have problems with the sound coming out of my bass guitar. The sound cut in and out and had some distortion and static. I managed to get through the last few songs by wiggling the cable and standing very still (to prevent jostling the connection). After I unpacked my gear, I set about finding and correcting the problem. I found two separate problems:

1. The bass->amp cable had an intermittent short in one end caused by a strand of the shield coming into contact with the signal conductor. I've seen this failure mode many times in guitar cables. The constant motion and bending causes the shield wires to fray and migrate around inside the connector. The fix was to cut off the stray strands, and wrap some tape around the center conductor in the connector.

2. The 1/4" phone jack in the bass guitar itself would fail if the plug was pushed in just the right direction. This bass uses active pickups and senses when the ring of the phone jack is connected to the sleeve (ie a mono plug is inserted into the jack) to supply power to the active pickups. This way, the bass will not run down the battery when it's not plugged into the amp. I am not sure which contact was failing intermittently, but it was probably the sleeve or ring. I replaced the phone jack with a 4-pin "mobile radio" connector. These connectors are very rugged and have a threaded ring to secure the plug into the socket. No amount of twisting or pushing will cause it to break contact. I used three of the pins (two are shorted inside the plug to provide the battery-saving feature). I made a special cable that converts the 4-pin connector on the guitar to a standard 1/4" phone jack on the amp. The only downside to this setup is that the plug cannot rotate, which is one benefit of the 1/4" phone jack -- it helps to get kinks and twists out of the cable while walking around or moving the bass around stage.

Anyway, I'll post about this again if it turns out to be a really bad or really great idea.

Improving Bing maps (formerly called MS Live Search)

Microsoft recently rebranded their "Live Search" maps as "Bing". The only notable feature is that it has a bird's-eye-view, which is lacking from Google Maps. I use the bird's eye feature often because online real estate sites like redfin, trulia, etc generate links to show the houses that are for sale. Recently, Bing maps became much less usable. Whenever the site loads, an obnoxious pop-up demands that I install the 3D viewer client -- complete with shady-as-hell setup.exe file. I don't see any way to permanently decline the 3D viewer. There is also a stupid list of mapped items on the righthand side of the screen. This might be a useful feature, but it should be possible to permanently disable (especially when there is only one thing in the list!). The left side of the screen is dominated by ads. Here's what it looks like:


Even after dismissing the popup with its annoying bandwidth-hogging flash movie, there is still very little map actually visible on the screen. The solution is to write a greasemonkey script for Firefox. This tool allows users to write javascript that is executed for a pre-determined set of webpages (like http://www.bing.com/*). Here is what Bing looks like after my greasemonkey script was setup:


Aahhh, that's so much better. It actually looks like a map now, and I don't have to spend at least three clicks closing stupid windows everytime that I see a Bing link somewhere on the 'Net.

Search for greasemonkey to find out more about this tool. Here is my script (note: I am a rank-beginner when it comes to javascript. I am sure there are numerous problems with this code, but it does work):




var preventlayer = document.getElementById('__preventLayer__');
if (preventlayer) {
preventlayer.className = 'boguspreventlayer';

}

var mainpopup = document.getElementById('help');
if (mainpopup) {
mainpopup.style.display = 'none';
}


var taskarea = document.getElementById('msve_taskArea');
if (taskarea) {
taskarea.style.width = '1px';
}

var mainmap = document.getElementById('msve_mapArea');
if (mainmap) {
mainmap.style.marginLeft = '0px';
mainmap.style.width = '100%';
}



document.addEventListener('DOMNodeInserted',function(){

var sidepopup = document.getElementById('msve_ScratchPad');
if (sidepopup) {
sidepopup.style.display = 'none';
}

},true);



var footer= document.getElementById('sb_foot');
if (footer) {
footer.style.height = '0px';
}


// hack to get AJAX to redraw the map after greasemonkey altered the map width
window.resizeBy(-1,0);

Drum practice and recording setup

In this post, I will describe the setup that I use to record my drums while practicing. I recently bought a Zoom H4 Handy Recorder. It works really well, and I think it is a worthwhile piece of equipment. One of its really nice features is the ability to connect two external sound sources and also supply phantom power. The device allows individual level adjustment for each source, and will also mix the two inputs into stereo. I have it setup with a Tama Rhythm Watch RW105 metronome, and an omni condenser microphone. The mic is normally used for testing the frequency response of home theaters and it has an extremely flat response from 20Hz to 20kHz. This doesn't necessarily make it a great overhead mic for drums, but it's what I have.

The output of the H4 goes into earbuds, then I wear large earmuff-style hearing protectors over the buds. This lets me adjust the volume of the metronome and drum kit (from the single condenser mic) very easily. I can also hit record on the H4, and make a quick track so that I can critique my playing very quickly. This setup has proven very useful.