Computing stuff tied to the physical world

Tektronix 475

In Hardware on Jan 26, 2012 at 00:01

Oh boy, I’ve been bitten by the collector’s bug…

Couldn’t resist an excellent offer on Marktplaats (the Dutch equivalent of eBay) for a fully operational analog scope built in the late 70’s. The Tektronix 475 is, ehm… slightly larger than the Hameg HMO2024:

DSC 2892

Then again, they are quite comparable – both are specified as 200 MHz bandwidth. Check ’em out:

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The Tek will need to be re-calibrated, but as far as I can tell all the functions work and all the switches, knobs, and indicators are in good order. The previous owner said he had used it for a long time, but not intensively.

First thing I had to try was the analog clock, of course:

DSC 2886

Apart from that? Oh, I don’t know. I’ll refurbish and re-calibrate it one day, there’s lots of info about this classic workhorse out on the web, and I really would like to learn how to diagnose and repair stuff. Even old stuff.

This is a single-beam unit, meaning it can’t show two signals at the same time. Newer and more advanced models are dual-beam, but this one has to either “alternate” between the two beam displays, or “chop” them up and draw bits of one and the other in an interleaved fashion. It’s also not a storage scope, so you’ve got to look very carefully if you want to see one-shot events – the display on the screen shows only as long as the phosphor glow lasts!

Fantastic engineering. Electronics, mechanical, operation, documentation, service – everything!

Would I have bought the Hameg if I’d had this one at the time? You bet – the “S” in DSO is a game changer, especially with microcontrollers and physical computing. But that huge Tek brick is more endearing :)

Heh, I’ve never before collected anything in my life – this is fun!

  1. Hmm, open with care, there is -18kV inside at enough current to do serious harm!

    The single beam is rarely a limitation since both options of “alternate” & “chop” (for slow waveforms) is available. The logarithmic nature of the eye’s response (and the high accelerating potential) is useful for rare events – with the brightness control high, even single events can be briefly seen. In normal use, brightness is kept as low as practical to prevent ‘phosphor burn’ where excessive excitation of the same area eventually reduces its response to the beam.

    Hence the origin of “screen savers” for old style CRT displays where a certain vendor’s logo shadow would get “burnt in” permanently. Curiously, screen savers are still used on LCD displays….

  2. “Heh, I’ve never before collected anything in my life – this is fun!” – It’s a virus, I tell you!

    Congratulations btw :)

  3. Eindelijke een echte scope :) Nice picture.

  4. “Newer and more advanced models are dual-beam”, this is not correct. Before the 475 some older models had real dual-beam capabilities but it became almost impossible to build a crt with high writing speed AND dual beam. Perhaps the Tek 7844 was produced after the 475 but I’m not sure.

  5. Ah, the memories :) When I was an electronics technician apprentice in the early 80s, we had one of those in our lab and was the “real good one” everyone tried to grab!

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