The eBay addiction starts small. One night you’re buying $3 buck-boost converters and cheap Chinese USB power packs. The next thing you know you’re spending thousands on dead instruments with no documentation. You’ve got the skills though, and if your bet that you can diagnose and repair a 14 GHz real-time spectrum analyzer is right, you’ll be putting a snazzy instrument on the bench for a fraction of the original $50,000 it cost.

Make some popcorn and get cozy before settling in to watch [Shahriar]’s video below, because it clocks in at just over an hour. But it’s pretty entertaining, and just seeing how Tektronix built the RSA 6114A spectrum analyzer is worth the time. Things are different when you’re piping microwave signals around the chassis of a beast such a this, the interior of which is densely packed with pluggable modules. Tek factory service would no doubt perform a simple module swap to get this machine running again, but [Shahriar] wasn’t having any of that on his $2,700 eBay find. After isolating the problem to the local-oscillator generator module, [Shahriar] takes us on a tour of where the signals go and what they do. We won’t reveal the eventual culprit, but suffice it to say that after a little SMD rework, [Shahriar] has a very fancy new instrument for the shop.

If this repair gives you the itch to get working on microwave circuits, maybe it’s time to build that backyard synthetic aperture radar set you’ve always wanted.

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