For almost a year, I’ve had a CDJ-100s that my brother inlaw gave me to repair. He picked it up second hand from his employer as broken, and was hoping I could fix it. Basic troubleshooting showed it wouldn’t read disks. You’d put a disk in, it would spin up, but then never show track info, or start playing. I did find the Service Manual online several places (linked here), but beyond basic troubleshooting, it required the “YEDS-7” disk, which is also called the Sony Test Disk 3. Which costs, from everything I can find, at least $150 (and has also been discontinued). So, it sat in my repair pile.
Fluke 12 repair
Another meter repair everyone! Anyway, as usual, I purchased a Fluke 12 off eBay listed as the buttons not working, but the meter itself worked as long as you were measuring diodes, or VDC. After a quick search online, this appeared to be due to the elastomeric strip between the buttons PCB and the main PCB being dirty, or failing. I contacted the seller to make sure the case wasn’t broken (as this meter seems to be on Fluke’s “Repair by Replace” list, I didn’t want to fall into that trap again), and after he said it was all intact, I ordered the unit for $30 + $6 shipping.
The meter arrived, and indeed, the buttons didn’t work. Nice “click” when pushing, but no registration. I pulled the screews from the back of the unit, and the main PCB clips into the case in a rather awkward way (really Fluke?). After getting that out, there’s a plastic/metal shield that holds the LCD and button board in place, and a cutout for the two elastomer strips to pass through. I cleaned the main PCB real well hoping that would help, but sadly, it still doesn’t work. I grabbed my meter, and checked the strip it came with, and it registered in 5 mega-ohms. Well, that’s not right. Online I found some references to stealing the elastomer strips out of a Harbor Freight cheapo multimeter. As luck would have it, I had one of those I got for free a while back. Indeed, it has two strips between the board and the screen, and while the height of them is right, the thickness is off (they’re just over 1/2 as thick is the stock strip). So, I cut two to the right length, and measured their resistance: about 5-10 kilo-ohms. Much better. I doubled them up and managed to shove them into the space where the old strip was, and closed the unit up. Once the screws were in (and therefore pressure applied to the strips), it worked! Total repair time, less than 10 minutes. Cost, free!
The story of the mis-wired XT60 connector and the DJI Phantom
I was recently handed a malfunctioning DJI Phantom Quadcopter that anytime the owner tried to lift off, it would just flip backward and crash. So, I went about recalibrating, and figuring out how to actually fly a Quadcopter. Anyway, I figured it out ((The “front” of the Phantom is determined by which end you point “down” during the compass calibration. According to their rather lackluster drawings, the “front” is the battery door side)). Anyway, I flew the unit around for a bit, then when the battery got low, the unit landed and showed me it’s wonderful flashing red light.
So, I brought it in, and plugged in the dead battery. As “luck” would have it, though, the place the unit was ordered from sent a free extra battery (RC-2220C3S) made by some other company (WATSON). So, I figured I’d try that. I checked the unit with a multimeter based on lead coloring, and saw it was at 11.2V, which is fine. So, I plugged the battery into the Quad, and was immediately greeted with flames, and a huge amount of “blue” smoke. I quickly unplugged the battery to figure out what the heck went wrong. An XT60 connector is polarized, so there’s no way to plug in backward. But, if you’re eagle-eye’d, you’ll notice the picture for this post, and something I didn’t even think about prior to plugging in the battery. The pos/neg (red/black) are wired backward! So basically 11.1V and all but unlimited amps (Lithium Poly battery) went up the ground plane, and anything that didn’t have polarity protection was fried (or at least the first thing to short was fried).