$2700 eBay Bet Pays off for this 14 GHz Spectrum Analyzer Repair

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.

74 thoughts on “$2700 eBay Bet Pays off for this 14 GHz Spectrum Analyzer Repair

    1. The video almost makes me want to cry. He’s got like a quarter million dollar’s worth of test equipment on his bench… It’s not just that he’s insanely better equipped than my home lab — he’s insanely better equipped than the lab we have at work!

        1. Actually, the unit had a base price of about $80,000 and the 110 MHz capture bandwidth card alone at list is about $12,300. So with some other options thrown in, (Shahriar did say it was pretty loaded) I’d say the unit msrp is about $140k. The $50k price is about what it’s worth on the used market today. Really nice job on the troubleshooting and the fix.

      1. I was thinking the same thing with an SSD. I’d probably take an image of the drive and try to toss it on an SD card that I could tape in there too. Pretty common to run into <100gb disks in instruments like that from that era.

  1. Support Shahriar’s “The Signal Path” (TSP) Site – I can’t emphasize this enough! There are too-few EE Blogs dealing with RF analysis & teardown. Don’t get me wrong, I love the likes of Dave’s EEV Blog site, but it is a virtual DESERT when it comes to serious RF stuff. EEV Blog and The Signal Path compliment each other, so support BOTH. But again I think Shahriar’s site deserves more support than it is getting. Yes the posts on the TSP site are less frequent than the EEV Blog, but look at the content and depth you get on the TSP site in comparison.

    1. Totally agree. I have watched every single video he has posted. I really appreciate people who have so much knowledge in their field and are happy to pass it on, more people like that and we might just fix the world. Education is the key. Thanks.

    2. Dave is a snowman. He does entertaining shows, but I rarely find anything really interesting in them. Shahriar does a great job not only taking on RF magic, but also explaining in detail what he’s doing and how things work. I already signed up to support him, and until he will not try to build a walled ghetto videos and posts accessible only for his supporters, I will happily put my money in the basket to help him bring more topics that nobody else has knowledge and courage to talk about.

        1. No. He had it right. Our favorite semi-hysterical Aussie performs great ‘snow jobs’ which give the impression he knows what he is talking about.

          Sadly, the reality is somewhat different…

          Even worse, as I and others have pointed out many times, there are very few alternatives.

      1. I have no intention of making my videos exclusive to my Patreon supporters. The whole idea is free and accessible knowledge for everyone. Support is voluntarily and appreciated.

      2. I think Dave’s pretty good. He’s clearly very knowledgeable though he’s often said in depth RF design isn’t his cup of tea (and in fairness it’s very few people’s cup of tea :) And the people that are into it would often be under heavy NDAs for the things they’re working on.

        But I like the way Dave makes electronics accessible. I’ve even heard some of my non-ultrageek friends taking about him.

        But I’ll definitely check Shahriar’s blog out now!

        1. Dave is very knowledgeable, but the videos he makes are addressed to less advanced part of the audience. That’s really great that he educates his viewers and helps start with the hobby; However, for more advanced hobbyists there is much less value in them.

    3. I think there’s a good reason there’s almost no content out there. It’s a REALLY expensive field to get into. Just a very basic chinese spectrum analyzer will set you back like $1500, and a basic VNA on the used market is about twice that… Add to that a bunch of other stuff (probes of all kinds, antennas, cables, attenuators and stuff) and you’re well outside the means of 99% of hobbyists. A Fluke 87 and Rigol DS100Z is already stretching most hobbyist’s budgets. It’s quite interesting but I’ll never have that much money to spare, even if I’ve started making some boards with RF stuff (using CC3100/CC2650 ICs)

    4. I completely agree with Drone. Shahrirar’s channel is one of the best RF / electronics resources on youtube. In fact, it is the best I’ve run across. I was going to support when I saw his call for it, but I couldn’t figure out how to without a Facebook account. Please add a paypal option or something like that Shariar. I will donate. You are the man.

    1. +1 for backup! Also check if the device only accepts HDD with a specific size or from a specific manufacturer or even with a specific ID or don’t no what. Seems like they are devices like that where you need to buy a genuine replacement (for $$$) from the original manufacturer (if he still sells these parts…) instead of a generic part (for $ only).

  2. This is a very interesting video by someone who is obviously extremely knowledgeable, but I don’t understand his ESD protection methodology. Grounding himself and leaving the equipment electrically floating while sitting on a towel doesn’t ensure he and the equipment are eqipotential.

    Perhaps his technique is better than nothing because I would guess a person is more likely acquire a large charge relative to earth than the equipment is, but shouldn’t there be a conductive path (through a high resistance for protection against shock, of course) between the person and the equipment for real protection?

  3. I once scored a Mortal Kombat (the first one) JAMMA board on eBay for $10.75, listed as “broken”. the board would reset constantly when tested. I just solved this problem with the Mortal Kombat JAMMA board (prototype version) I already had, and gambled on the issue being the same with the broken one on eBay.

    the board worked just fine for me. turns out the problem (for both boards) was the +5 voltage out of the power supply was set too high. quick adjustment with a small screw driver and a multimeter and everything was good to go.

  4. Have similar issue with a “sneaky” jukebox. If you take out the CMOS battery even if flat it wipes everything, causing Windows not to boot.
    Never seen this before, even resetting to default does not work.
    Little hint: sometimes they do this on purpose and use a dummy battery with no contents to force a reset on every boot, because the default is to power on with a flat battery when mains is connected.

    +1 to copy the HDD, I use Winhex ™ well worth the $79.
    Be nice and pay for the upgrades, Mr Stefan will appreciate it and he needs the money right now.

  5. Did this sort of stuff everyday when I worked as a bench tech. Probably repaired several dozen spectrum analyzers. Don’t recall any of them defeating me. I’d have taken the chance without worry.

    1. (I will admit however that I had real test equipment behind me when I repaired all those units. My home bench is far more modest, though I do have an 18GHz counter, rudimentary RF network analyzer, and RF power meter. This repair looked a bit beyond my availzble equipment.)

  6. Sometimes the gamble works out, sometimes not (which is why it’s a gamble). In the past I’ve found some gems on ebay, but not always. I once forked out over $100 on a Fluke 1061 synthesizer… had only scrambled display on power up….only to find it had been gutted of just about every board except power supply and front panel. (I still broke even on the deal because they missed the 127db output attenuator. ) Had it not been for that one useful component I would have had just an empty box.

  7. Another amazing video, I think it’s great the way you explain ur thought process! Keep em coming ! Oh, how much do u want for the wireless ESD strap? mine has become intermittent !

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