EEVblog #196 – Tektronix 2225 Analog Oscilloscope

30 minutes of Dave twiddling knobs on a 2nd hand 50MHz Tektronix 2225 analog oscilloscope – it’s right here!
Who else can get so excited about a 500uV/div vertical scale?

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  1. The noise on ch1 might be coming from a pulsed on/off signal to the “power on” LED just to the left.

  2. Dave,
    One of your BEST videos for the hobby crowed! Thanks!

    Are you using a new camera? This video seems much sharper, clear and focused than others. Or is that just because it is closer or better lighting?

  3. My Tek 465 took a dump on me about 3 years ago and I’ve not replaced it yet. I’ve got 2 DSOs and just didn’t feel the need to rush out and get one. I look on ebay from time to time but I’m one of those people who isn’t interested in a good deal, I want theft. So I shop. After seeing this, I took a look on Ebay this morning and I gotta tell ya Dave, if you thought these were cheap in the US, think again. These people are smok’n meth over here! Even old 465s bring brand new Rigol $, and that’s from the completed listings, not asking price. There appears to be some occasional deals too, but its amazing what variation there is in pricing.

    Then too, I picked up a trinket last night that I was the only bidder and paid <$25 incl shipping. Looked when it finished and there's another listing for the exact same item, 26 bids, $440+shipping, and still going. ????? Whatever… :shakes head in disbelief: If I could find some idiot to buy my 14402 8ch Tek for 10x what it's worth, I'd be seriously looking at a new Agilent 3k.

  4. I dearly love my Tek 485! My wife hates it because it’s huge. She even implied that I could get a Rigol soon, because it’s smaller, but I can’t bring myself to consider replacing it! 🙂 b.t.w., I got it on eBay in 2002 for $300. Worth every penny!

  5. I would suspect that the extra voltage you see is probably not due to the instrument producing the wrong output swing, but rather due to the setup. You are relying on a 12.5Ohm resistance, however I believe that the cable, BNC connectors and T-junctions probably introduce an extra Ohm. That would make the overall resistance 13.5Ohm which accounts for the extra voltage you are reading.

    • Similarly, how accurate are those termination resistors? 1%, 5%, 10%?

      Any variation in those will also affect the p-p. Would have been nice to see the waveform going straight back into the Agilent without the terminators.

  6. Dave,

    Thanks for this video! I’ve been thinking of picking up one of these cheap scopes on eBay. Your video has given me confidence that I will be able to verify its basic operation when I get it.

    Please consider a video showing how you perform the calibration of the vertical channel & timebase. (or maybe include it in your teardown video.)

  7. Dave,

    Great video, I came across one of these a while ago and it’s been sitting in my lab waiting for me to pick up some probes. I’m not familiar with this instrument, could you recommend some probes? Also why didn’t you use the CAL adjust knobs to adjust the voltage / time issues?

    • The “Cal” knobs aren’t really that!
      “Cal” is the default position of the variable
      To adjust the calibration,you need to put the control in the “Cal” position & do the internal adjustment.

      The calibration error does not preclude accurate readings,as you can adjust the variable control to match some known standard & then do whatever measurement you want to do.

      This is just a work-around,as if you return the control to “Cal”,the ‘scope will still have the original error.

      The variable controls are very useful if you want to express the amplitude of part of a signal as a percentage of another part,or to fit a waveform into a “go”-“nogo” graticule.


  8. Congratulations, Dave!

    A few years ago, I got a Tek 2232 scope on eBay for $300. I paid much higher than the average going price because at the time, many of the eBay sellers of old Tek scopes were offering them “as is”, with no guarantee of proper operation. That was too scary for me! I waited patiently, and one appeared that was sold by a used equipment dealer, described “in proper working order”, with a 30-day warranty. Perfect. And it was in good calibration, too.

    The Tek 2232 is in many ways like your 2225, but it is actually a 100 MHz DSO that also has an analog mode. I can switch from digital to true analog with the press of a button! It’s really cool. It doesn’t have the 500uV/div vertical scale mode that you love, but for me, it is the perfect model. I remember reading about introduction of the model line in Electronic Design around 1991, and I really wanted one, but it was over $5000. At $300, it was a steal!

    I really want to see the teardown of your 2225, and the calibration procedure!

  9. Hi Dave,

    thanks for another good video. I got a Hameg 1005, which has the same timebase error. So I am also interested in how to correct this error in generally.

  10. The scope can also be run on 11.8 – 30.0 VDC battery power with an internal OPTION 07 DC inverter mounted:

  11. Please show the video of you adjusting the internal pots!

    Great video, really helped me realize that I want to buy an analog oscilloscope instead of a digital one!

  12. That BNC cable you are using….Is there an ohm rating that should be used for connecting something like a scope to a function generator? And what about using just a bnc to alligator clip cable, at what frequency should you switch to real scope probes?

  13. Wouldn’t it be more probable that the 50ohm resisters are slightly off ( within the tolerances ) causing your voltage to be off by a bit?

  14. Thanks Dave!

    Seeing how to calibrate a scope would be really interesting =)

    Thanks again for all the cool vids 😀

  15. Hey if you ever get the service manual please mail it to me ^^
    I got a 2225 too and i’ve read that after some years the input filter is known to fail on this model and should be replaced with a new 3A to 5A integrated filter…..

  16. Me need TEAR DOWN VIDEO of the 2225 !
    You provide TEAR DOWN VIDEO ASAP or Borat comes down under and tear up something


  17. Hi Dave,

    Very nice video. I have been using a similar Tek 2235 for many years mainly repairing old HP calculators.

    I’d very much like to see a teardown and/or calibration video!


    — Dan W

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