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Build CobaltFlux control box

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Cobalt FluxEver since my first CobaltFlux control box died, I’ve wanted to have a plan in place for a replacement should the current one die. Sadly, CF is out of business, so options are rather limited. But, the internet is a resourceful place, so I was able to quickly find a place to find plans for making a replacement.

It involves buying a generic USB to game stick adapter, and then soldering on the connections from a DB-25 (VGA) connector. In this case, I bought two of these. I removed most of the connectors, and just soldered wires directly to the pads for each “direction”. I then used a Hammond 1591BBU (blue) project box. Cutting a hole for the DB-25 connector is a pain in the but since it’s not square, but it turned out okay. I used a “dremel” cutting bit for my Proxxon to cut the hole just big enough to pressfit the DB25 connector, and cut a relief for the USB cable, and holes for the top “Start” and “Select” buttons. Mounting the board in the box was just a little hot glue on the bottom of the board.

Total cost for the parts were about $20. The soldering is simple, it’s mainly just doing the drilling on the enclosure. Total build time was about an hour, including testing. It’s a very easy build, and it thankfully works. =)

Good luck if you build one. I think I’ll build at least one more as a spare. This one described here was for a friend. =)

Tektronix 2465 300Mhz 4-channel oscilloscope repair

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Tektronix 2465On a recent trip to Portland, I stopped by Surplus Gizmos, and found a used, as-is, Tektronix 2465 scope that had a calibration sticker on it saying “unit smoked while calibrating”. The scope was listed as $100, but I was able to get it for $60. I know the unit isn’t worth a ton, but it is a 300Mhz scope, and is seemingly considered one of the best Tektronix scopes ever (it’s also considered the last repairable Tek scope, as after this, most scope manufacturers stopped including schematics and other information with the scope). Also, the unit showed to have been manufactured around 1984, which is when my grandfather still worked at Tektronix writing manuals for scopes. So he may have very well worked on the manual for this scope.

Opening the scope up, I figured the issue was going to be the power supply, as that seems to be the common failure in this scope, and really any device of this age. The capacitors dry out, change ESR, overheat, blow, etc. Getting the fan off was really the hardest part of getting the power supply out, but once I figured that out (and broke the mandril holding the fan. =/) I got the PSU out, and quickly found the failure points ((Note, to remove the fan, you loosen the nut, then holding the fan “cage”, PUSH on the nut-screw toward the scope. That will push out the mandril and release it from the shaft. If it won’t release, please be careful. I got lucky and my mandril broke in a repairable way. I’ve seen pictures where they completely shatter, and there don’t seem to be any replacements available)). One of the caps on the low voltage side had ruptured, and also R1016 and C1016 on the mains input were both blown. There are plenty of online guides about re-capping this scope, but the only one I found with actual part numbers and quantities was here. His list is for the 2465B, but the 2465 is very similar as far as the PSU, the main difference is the lack of the SMD caps that everyone says to replace. Instead, there are three through-hole caps on the Digital board that you can replace.

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Fluke 8021B LCD Repair 2

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8021b-screenKnowing 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.)).

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