Keithley 196 Repair #2

KEITHLEY_196I recently acquired another Keithley 196 off eBay that was listed as not powering on, which, could be a lot of things, but hopefully was related to the power supply/rail infrastructure (thinking, most likely the digital logic 5V regulator, primary filter cap, etc).

The unit arrived, and indeed, did not power on at all. No indication that the digital side of things was getting any power at all.

So, opened the unit, and pulled the analog board/enclosure off, and didn’t see anything. So, I pulled the digital board, and wow, the PCB was all brown/burned around the transformer. Sadly, I didn’t take a picture. =( Seemingly, and this is a guess, there was a cold solder joint (either from the factory, or from vibration) on the pin in question, and it heated up over time to the point of burning the pad it was soldered to, which killed that power rail. Tracing out the adjacent pins revealed that the pin in question was related to the 5V digital rail. Viola, we have our issue. Obviously, I’m hoping that the power supply going out didn’t damage any of the digital board.

The biggest issue with the repair was getting the burned pin to take solder. It required a fair amount of sanding with some 400grit paper, then cleaning that up a bit with some 1500grit (didn’t have anything between those two). =P Then, it was just a matter of bodging a wire (in this case, a 20awg stranded wire) between the transformer pin, and the bridge rectifier for the 5V digital rail. Then just tack the wire down with some hot glue (I don’t like wires just flapping about.

Keithley 196 #2 FixI also re-flowed the solder joints for the rest of the transformer pins, as I bet the issue was just poor soldering at the factory… the PCB also flexes a bit in the enclosure, and the transformer weighs a bit (which is why they bolted it to the PCB in the first place). The picture to the left is obviously my repair. I put the unit back together again enough to test (put the digital board back in the enclosure, plugged in the front panel (display, etc)), and powered it up. Bam! Works! So, put the unit back together fully, and tested it out. It’s about 20mV off from my other 196, and my 199. So either they’re both off (which wouldn’t surprise me since I nuked the configuration on the 199 at one point), or this new one is off. One of these days I’ll actually get one of my meters calibrated, but at this point, they’re very accurate, and pretty darn close. Remember, in the 30V range, the 196′s least significant digit is measuring 10uV’s, so 20mV’s is both a lot, and not very much. =)

Job accomplished.

Personal Update — 8 Months

Sean StairsJust thought I would take a moment away from the normal geek-ness of my site, and do a personal update. About 8 months ago I posted that I had just had a baby son, and yay verily, 8 months later he’s grown up quite a bit (see picture). He has long since gotten his first tooth (Christmas day, 2013), and 3 more. He’s working now on tooth 5. About two weeks ago, he figured out crawling forward (he’d been crawling backward for at least a month prior, and was quite good at it). And shortly after figuring out forward crawling, he started finding all kinds of new things to “pull to stand” on, like the stairs (hence, the picture). =) So, that’s been fun (baby-proofing things he finds that we didn’t even think were likely to be found). =)

The only issue has been, the little guy doesn’t sleep well. At his best, he was sleeping in 2 hour chunks. Lately, this has been hour, at most, chunks. Turns out much of this was due to him having ear infections, which we’ve been fighting, and seem to have under control at this point, but lately he brought home a “wonderful” cold from daycare that both my wife and myself caught, and have been “dying” from the last several days, all the while he’s been crawling around wanting people to play with. ugh. But, we’ll all get better.

In short, parenting is interesting. It’s both exceedingly enjoyable and exceedingly frustrating, and given previous experience, as the little boy gets more able to interact with me/us, that scale will begin to tilt more and more toward the “enjoyable”, as most of the “frustrating” comes from him not being able to communicate in any real way. So, maybe it should be said parenting is all about patience…

Mac Mini 2009 SSD Upgrade

Apple Mac Mini ServerBack in July 2011 one of the stock Western Digital HD’s in my 2009 Mac Mini Server went out, so I bit the bullet and purchased two new Western Digital Scopio Blacks (both 500GB), and RAID1′d them together. Fast forward to a couple weeks ago, and my RAID goes offline. I run several days of block checking, and find that the upper drive has gone out (which, I’ll get replaced by WD, but at this point, I’m looking to replace both drives… and I generally don’t trust refurbished drives). Anyway, figuring two new 500GB drives would cost about $100, I started looking at alternatives, and quickly found the Crucial M500 240GB SSD for $140 through Amazon. I then wouldn’t RAID drives together, I would just put OS/Services on the SSD, then use the still functional 500GB Western Digital drive as storage for larger files (downloads, backups, etc).

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