Tubes Have Character With A Tek 570

When tubes were king, you could go to a drugstore with a box full of them from your TV. There would be a tester that would tell you what tubes were bad and, of course, you could buy the replacements for them. That kind of tube tester was pretty simple. If you wanted to really know how to design with a tube or test its parameters, you were much better off with a curve tracer like the Tektronix 570 that [tomtektest] shows off in two recent videos that you can see below.

That piece of kit fell into [Tom’s] lap thanks to an observant delivery driver. The 1955 instrument is very similar to a semiconductor curve tracer but, of course, has the ability to provide much higher voltage for the tubes. The basic idea is that the X axis sweeps from a few volts up to 100s of volts. The vertical scale will show the plate, screen, or grid current. From those curves you can learn a lot about the characteristics of the tube.

Accommodating the various tube pinouts takes a patch panel that would be at home on an old-style computer. You might wonder why you’d need all this data on a commercial tube. Like transistors, tubes had published data, but no two tubes would be exactly alike. It was very common in certain circuits to hand sort tubes of the same type to find tubes that closely matched.

[Tom] does a nice job of taking us through the device’s block diagram, shows us some of the schematic, and — of course — demonstrates the operation. He even shares some hacks to fix some oscillations in the tester’s circuits. While we don’t miss lugging those heavy beasts around, but somehow using an instrument with a screen that weighs more than 25 pounds makes you feel like you accomplished something.

If you want to build out your own tracer for solid-state instead of hollow state, it isn’t that expensive. Of course, one of these old 570s would be just the ticket if you were building your own tubes.


12 thoughts on “Tubes Have Character With A Tek 570

  1. This does bring back some memories. I was schooled decidedly during the semiconductor age, but was, literally, the last year where tubes were in the curriculum, and we did a couple labs with tubes. I never used a 570, but there was one in the lab. The radio station transmitter was tubebased (mostly), and I did do some work with that. It has actually been a number of decades since I professionally used a tracer of any kind- when I left the semiconductor fab side of the world, several carrers ago.

  2. We have a Tek 576 at work, in part because it can get to 1500V and for very quick pulses can produce 200A, which is useful for our design verification.
    The environmental safety and health people _hate_ it, and for good reason. That thing could kill you so dead even your children’s hair would rise up.
    High voltage curve tracers are still quite useful even in some semiconductor design areas.

    1. Damn. That is some impressive wattage. That goes through a little patch cable panel like on the 570? I could see why it would raise some eyebrows safety-wise to say the least! What components would one test with that kind of power? Some kind of very heavy-duty vacuum rectifier maybe? Just curious.

      1. Not both at once: I think at 1500V it’s limited to 350mA, which is still enough to kill an elephant. The 200A pulse involves a big cap bank discharge, and I don’t know the voltage limitations on that. (I’ve been trained on how to use it but I don’t because it’s terrifying and I can avoid it.)
        We use it for characterizing electrostatic discharge structures on pins in our IC’s, because for various reasons we have another group in the company who designs standardized ESD for each silicon process we use, and sometimes what they do and what we do interacts poorly. Like, the chip fails a standard body model ESD characterization and we suspect it’s because the ESD structure has shorted to the underlying substrate, rather than the problem being in our design. Those tests often require 1 or 1.5KV, albeit at way less current, and sometimes we have to do them a couple hundred times and see if the threshold is shifting.

      2. It’s useful for repeatedly stressing the electrostatic discharge protection structure on a pin and seeing if its threshold changes over time. I think the 576 is limited to “only” 350mA or so at 1500V. The 200A is a big cap bank, and I don’t know what voltage it fires at.

  3. “While we don’t miss lugging those heavy beasts around, but somehow using an instrument with a screen that weighs more than 25 pounds makes you feel like you accomplished something.”

    Mechanical adding machine, and I’m glad those days are over.

    1. The common phrase in today’s job ads is “Must be able to stand and lift at least 50 pounds.” Time to get working on that Ironman suit.

      “While we don’t miss lugging those heavy beasts around, but somehow using an instrument with a screen…”

      “While” or “but” but not both, m’kay? That’d be great.

  4. i´dlove to see a decent, micro-controller based, open source tool like this where i can characterize and sort my big box of tubes accumulated from childhood. All what i found is that a few good, 50-70 tube testers are worth a lot of money. Out of budget !
    And it´s too much a niche market that China would step up and produce decent, affordable tube testers.

    Is there any solution ?
    I could use my networked lab tools, all controlled by Python Script, unfortunately I have to Power Supply that can reach that needed high voltage, and it is also limited to DC …

      1. I built mine and it is awesome. He’s now working on version 6 (having dropped versions 4 and 5 due to less than stellar results by his own requirements). It does the job of multi-thousand dollar tracers out there and has a huge community behind it. If you want to get into tubes, and want to be serious, this is the first piece of kit to buy and build.

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