Archive for February, 2011

Fixing a DLP rear projection TV.

A few years ago, my uncle had a big screen TV that was starting to go bad. The color wheel was misbehaving, resulting in distorted colors, and sometimes an unstable image. He had an estimate for repairs, and since Sharp doesn’t sell just the color wheel, the whole projection assembly would have to be replaced, from something like $1400. Definitely not worth it, so my uncle got a new TV and gave me the old one. I used it as it was for a short while, but it slowly got worse, and I grew tired of dealing with it.

I decided to take it apart and have a look, to see if I could replace just the color wheel if I could find a source for one (same model TV on Ebay, broken, but with a different issue). I took the back off, pulled out the light engine (the projection assembly) and opened the chamber containing the color wheel. I didn’t feel any problems with the spindle; there was no sticking at all. I saw that there was a thin whitish film on the color wheel, so I took the wheel out and cleaned it with Windex¬†(probably not the best idea, but it hasn’t been a problem so far). I then noticed that the outside of the motor had the same film on it. The outside of the motor case what shiny reflective silver, and it had a black sticker on it, and there is an optical sensor to make sure the wheel is spinning at the correct speed (10800 rpm I think). I figured that the film came from the chamber getting too hot, and when it got hot after a couple of hours of use, the optical sensor would misread the speed and the TV would try to compensate, resulting in all the problems I was having. I cleaned off the motor housing with Windex and put it back together, and it worked.

I still wanted to get a spare color wheel, just in case, so I contacted a seller on Ebay who agreed to send me just the color wheel. I had offered to make him a guide to take it out of the TV, and he said he would want that. So I took the TV apart again, but this time I took lots of pictures. Once I had it apart, I thought why not make a guide on how to fix the TV like I fixed mine, so others with the same problem can fix it themselves. I documented the whole process, and wrote it up on Instructables. Before this guide, I couldn’t find any info on repairing this TV, only others with the same problem. I’ve gotten comments from a few people saying they were able to fix their TV with my guide. The Instructable is here:¬†http://www.instructables.com/id/How-to-fix-your-Sharp-56DR650-with-color-wheel-iss/

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Keyboard Light

Over the summer a couple of years ago, I started to use my (quite old) desktop to play some computer games. I was playing in the dark, and couldn’t see the keyboard to type anything, so I decided I wanted to make a keyboard light. I didn’t want to ruin the night vision I had gained from being in the dark, nor to distract from the game, so I decided I wanted the light to be red, or as close as possible. I went scrounging for LEDs I could salvage, but all I could really find was a hard drive mounting cage from a server that had orange surface mount LEDs (1206 I think).

Hard drives mounted in a similar unit:

The board I removed the LEDs from, it still has 2 green LEDs for each drive:

I removed all 6 orange LEDs, but since they were SMD, I couldn’t easily just solder wires directly to them, so I cut up a protoboard and soldered the LEDs to those pieces, and soldered the wires to that:

I then cut a long thin strip of cardboard and mounted the LEDs on that, equally spaced:

I wanted the LEDs to have a standalone power supply, but because most of the wall warts I have are unregulated and not switched mode, they can fluctuate voltage with current quite a bit. I was playing with lasers a bit at this point, and had an LM317 constant current driver (I think the design is attributed to someone called Daedal on laserpointerforums.com) that was good enough to drive a laser diode. Laser diodes are much more sensitive than LEDs, so it was overkill for the LEDs, I probably could’ve just used a resistor, but since I had it, I figured why not use it. The driver is fed right form a 12v wall wart (I think 300mA). Here’s a closer picture of the driver:

Lights on:

I have the lights on their own switch on my power strip, so I can control them¬†independently from everything else and only have them on when I need them. Here’s what it looks like from a user’s point of view:

It works quite well; I use it whenever I use this computer in the dark.

Christmas Sign

A couple of years ago at the beginning of December, my roommates were joking around about Christmas lights, and about how we could put up a sign with a pun about our address (we lived on Mary Street) saying “917 Mary Christmas”. We put of a few Christmas lights, and we tried to spell it out just by taping the lights to the side of our house. This completely failed, so I decided I had to figure out how to make a proper sign. I went home and scrounged through my mom’s garage and found some scrap foam board insulation. I printed off some giant letters (1 letter per page) and punched holes in them for where the lights should go. Picture soon:

I measured out and taped the letters to the sign and marked where the holes would go for the lights. I then used a screwdriver to poke holes in the foam board for all the lights, and used 3 strands of lights to spell it out. It turned out a bit better than I expected:

I then had to figure out how to mount it outside the house without screwing into anything (i.e. with just tape). I made a wood frame out of scraps in the basement, then screwed the sign to the wood frame using large washers. There was a square frame, then a piece of wood in front of the bottom to keep the bottom of the sign from being pushed forward off the front. This way most of the weight of the sign as resting on the bottom, and the front wood and screws just kept it from falling over. To mount it outside, there was a small (less than 1 inch) window sill sticking out past the brick on each of the 2 front windows. With the help of my roommate, we put the sign across the two windowsills, and put tape from the lower board in the bottom of the window, again holding the sign from falling off the windowsill, but not holding any weight. We then ran tape from the top board to the tops of the windows (and in the window) to keep the top of the sign from falling over. This turned out to be quite strong, the sign showed absolutely no signs of falling, even through all the snow and rain (we left it up for quite a while out of laziness).

Here’s what our house looked like for Christmas that year:

Needless to say, our electricity bill was quite high that month, but I think it was worth it.

Rock Band Pedals

A common problem with the rock band pedals is snapping in half. When I started playing RB drums, I didn’t have any problems or worries about this, I played heel down all the time. I went through drum kits like mad (thankfully I got a decent one before they stopped replacing them), they broke quite easily; they’d either stop responding to input, or grow overly sensitive to crosstalk. Anyway, once I got to the hard or expert level and started playing songs with a fair amount of bass pedal, I switched to heel up style. Some songs are much easier, especially some of my favorites, like songs by The Who. If played heel down style, my leg usually cramps up and I can’t play at all after that.

Playing heel up style puts a lot more pressure in the middle of the pedal, where it’s unsupported and not reinforced. My pedal broke rather quickly after I started playing heel up style.

I had my pedal replaced under warranty, but the warranty was limited and the design flaw wasn’t being addressed. Rock Band 2 tried to fix this problem (but caused another) by covering the top of the plastic with a thin piece of metal. This way the pedal flexes less and is held together even if it snaps. However, this just caused the pedal to snap right above the hinge instead. I didn’t want to suffer from endless broken pedals, so I decided to make my own that wouldn’t break. I don’t have a 3d printer, or metal working tools, so I built a pedal out of what I could work with: wood. I first built a single pedal out of pine; I made it twice as thick as the stock pedal, but all the other dimensions were the same. I just had to take the pedal apart at the hinge, transfer the mounting hardware and magnet (used to trigger the reed switch that connects to the rest of the kit), and it was all set. It was a rough cut, and made rather quickly, so I didn’t like it (it also wasn’t a great piece of pine). It worked great though. I decided I should make some out of hardwood. I bought the smallest piece I could find, I think it was oak, and decided I would make some wood pedals. A family friend has a good woodworking shop in his house, so my dad and I ventured over there and made 10 pedals, 5 each for rock band 1 and rock band 2 style bases. They have nice routed edges and feel very nice. I’ve been using mine ever since and I’ve had no problems at all. The original plan was to sell them online, but I never ended up doing that (Anyone interested?).

Top and Bottom of pedals, ready for mounting hardware:

Pedal on a base:

Pedal on base showing mounting:

I eventually bought an Ion drum kit (from craigslist, it was in my price range there), but I didn’t like the pedal that came with it. Luckily, it’s just a basic open/closed switch just like these pedals, so I soldered together an adapter real quick and now use this pedal with the Ion. Adapter: