EEVblog #593 – HP53670A DSA Repair Part 4 – Thermal Testing

Dave continues the investigation into repairing the HP 35670A Dynamic Signal Analyser. This time using the Flir E8 thermal camera to check for any overheating components on the suspect A5 analog board.

Part 1
Part 2
Part 3

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  1. How hot is that diode to the right and above the row of three AD845s on the left side of the board?

  2. Surely for simple components like op-amps, you could just probe the inputs, and that old favourite “op-amp action” will be trying to keep the inputs the same.. if there’s a huge difference, then there’s something amiss.

    Btw.. Why “The old dart” referring to Blighty?

    • Probing the inputs sounds like an effective and simple way to verify that an op amp is behaving sensibly – one of the best ideas I’ve seen in a while!

      If a lot of the op amps are the same, it should be an easily repeatable test, hopping from amp to amp and testing the same two pins.

      If you used a DMM with high input impedance compared to the ciruit impedance, the results ought to be reliable.

      If injected noise is an issue (i.e. a high impedance circuit), you could always add a small capacitor between the probes to kill noise and make a pure DC measurement even in high impedance circuits…

  3. I always fun to learn new phrases from Dave. First time I’ve ever heard the expression, “Extends out like a dog’s hind leg”. LOL…

  4. Well, there’s also “tiny as a bee’s dick” that I’ve never head of… 🙂

  5. Hello,
    Time to follow indication given by the display !

    Error 2 : I2C bus not receiving any response from devices. Why ?

    Page 10-11 says A7 is first probable faulty board. Hope not and try to follow page 4-24 to locate/eliminate this error 2.

    Analog is behind digital circuitry. Until digital doesn’t respond, no need to check analogs op-amps.


  6. Now as much as I like you stop dicking around with the fancy toys ,that most can’t afford.
    Your always telling us “Check voltages” so practise what you preach, stop looking for the lazy cure, there isn’t one. You should have that going by now. Get a wiggle on, cut the excuses.

    • Voltages were checked and fixed in previous parts.

      • Obliviously not well enough 😉 , if the job hangs around for more than a couple of days, then he would be on my pink slip radar,if you think I’m joking my boss is much worse. You can tell when he’s pissed off, he runs his finger a long the top checking for dust.

        • We waited so long for part IV that I thought it had gone the way of the Lecroy…
          Don’t forget it still needs to PSU to be repaired (again and properly this time), before it can run on mains.

    • Thermal checks are a proper part of troubleshooting. That’s all this video was, quick test with a thermal camera, I thought it might be useful to some people. Obviously not to you, oh well.

  7. I don’t know if you have this or not so I am leaving a link here: it is the service manual.

  8. As you have a desoldering iron gun it would be more easy to desolder the 20 op/amps (maybe 20 minutes or less) and test them in a breadboard with a test circuit (for example an opamp oscillator circuit)

  9. I am no engineer but I have to say that I love this series and I wish that I could help you fix it. I love the diag videos and I learn so much from them. Ps Dave I live in the USA but if I ever venture down to Australia I will Definately stop by.

  10. How about replacing one of the “hot” op-amps and see if there is a temp difference?

    Someone above mentioned fixing the digital issues first: might we worth a shot. If the I2C bus isn’t working right maybe the main board can’t talk to the ASIC on the analog board?

  11. I like the valuable information you supply in your articles.I’ll bookmark your blog and test again right hereregularly. I am slightly sure I will learn many new stuff proper right here!Best of luck for the following!

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