Knowing no end to my suffering, I realized I enjoyed repairing a friends Fluke 8021B so much, that I bought my own off eBay for $20 and decided to repair it. Checking the meter out before the repair, everything seemed to work just fine, including the historically amazing continuity beeper ((the whole reason I bought it, since it has a trigger time of 50µs (that’s 50 micro-seconds, or 0.00005 seconds). Meaning it only has to see continuity for that long before the beeper sounds. So you can quite literally sweep along an IC pretty fast to find which pin may/may not have continuity to your test point. Thankfully, there’s also a pulse stretcher that means even if you only have continuity for those 50µs, the beeper will sound for at least 200ms.)) ((And yes, theoretically the 8060a has a faster beeper, but… okay, fine, I’m a meter collector, and I couldn’t turn down an 8021B for $20.)).
Fender Frontman Reverb Repair
Ages and ages ago, a coworker brought me his Fender Frontman Reverb amp saying it didn’t work. He had a second one that did work, so there wasn’t any rush to get it working, so I took the unit home, and went to work on it. Disassembly was easy enough, and finding the schematics showed that the unit was identical to the Fender Frontman 15R, which has schematics (in the service manual) here. The US Fender site SAYS it has schematics for the 15G-15R, but only the 15G is shown, meaning the whole reverb section is left out. =/
Repair of Nikon SB-600 Speedlight
While loading the car for a shoot several weekends ago, I proceeded to drop my Nikon SB-600 from about 2 feet high onto the tile of my mudroom. I thought “crap, hope that survived”, and finished packing. I set up at the shoot, and my wife (who’s the actual photographer) started shooting, but complained the flash wasn’t working. Looking at it, the screen was misbehaving, it would flash inconsistently, and then after trying to power cycle it, it wouldn’t come back on. Uh oh. Shaking the flash, I heard rattling. Crap.
While the shoot was going on, I started looking online, and as it turns out, this is extremely common. It appears that the battery compartment rests on top of a large SMD inductor, that when the unit is dropped, with batteries installed, the impact crushes that inductor, which usually takes out the diode above it. See the ifixit article. Anyway, after the shoot (one flash down) a got the unit apart, and found that indeed, those two components were damaged. Also, while sifting through the rubble of the crushed inductor core, I found a 3 pin SOT-23 device. After looking, it came from the ZD301 spot. A zener diode. Huh. It’s marked 431, but it doesn’t appear to be a TI LM431. Some searching got me to a Russian site that indicated the unit was an RD43B-M, or a 43V zener! Apparently it’s some protection for signals coming in from the hot shoe (I think). No idea why it’s 43 volts, but…