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Design, build, hack....zap and repeat!

New Tech Toys Pt.2

Posted on Jan 5, 2014 | Comments Off on New Tech Toys Pt.2

On to the workbench! The holidays brought an abundance of technology which I started to describe in Part 1: Overcome with technology.  Now I’m headed down to the workbench. Since I work on mobile and desktop radios, transceivers and associated equipment, many of which use 12 – 15VDC, I got a power supply dedicated to that voltage and amperage range. And since much of that equipment just plugs into the vehicle’s cigarette lighter, I chose an MFJ-4245MV which just happens to have a cigarette lighter jack built right in! While testing the transmit side of these radios, you somtimes need to measure the output power. So I got a dummy  load / wattmeter to measure the wattage while transmitting into a 50 ohm “antenna” without going out on the air. I chose the MFJ-267 since it could handle up to...

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Tracking down bad caps

Posted on Jul 29, 2013 | Comments Off on Tracking down bad caps

I just added a new tool to the workbench and I’m loving it: Atlas ESR70. I work on a lot of power supplies, computers, transceivers,  LCDs, printers (you get the drift, right?) and find that capacitors don’t always have to “leak” to be bad. Here’s a pic of some bad capacitors. Easy enough to spot the bad ones, right? After replacing the three bulging caps though, the system did not come up. The ESR meter allows me to test for the equivalent series resistance in circuit, which is often impossible with a capacitance meter or DMM. And this particular model of ESR meter discharges a capacitor before measuring. . . so no blown meter innards. An ideal capacitor has a zero equivalent series resistance, and failure of a capacitor can be seen as an increase in its ESR. Well, the...

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