Products > Test Equipment

Does old test equipment really ever become truly obsolete?

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AG6QR:
I'm on the board of directors of my local ham radio club.  Ham radio is a hobby for all ages, but it definitely skews toward the older folks, who learned on old gear and sometimes still enjoy using it.  When older members pass away, widows often donate gear to the club, and we get to figure out what to do with it.  We have a few tube testers (these used to be found in the back of any retail store that sold tubes). We have many analog multimeters.  The high-end Simpsons are still useful and sell for a pretty penny; the $7.00 Radio Shack meter from 1978 might still work as well as it did when new, but it's hard to find anyone who wants to use it, since the cheapest digital meter is better in almost every way.

Really old gear, made with vacuum tubes and point-to-point wiring, can almost always be repaired to like-new functional condition.  The circuits are usually relatively simple, and wiring can be probed relatively easily.  Tubes and inductors rarely fail. Resistors and capacitors can be replaced with modern substitutes that often work better than the originals. Schematics are surprisingly likely to be available online (if not in an envelope inside the equipment itself). Old hardware like switches can sometimes be a bit of a problem, but usually not insoluble.

But gear from the early age of integrated circuits is a lot more difficult to repair.  And when software and firmware enter the picture, good luck!

We've got quite a few CRT oscilloscopes.  Early scopes that lack triggering circuitry are like that cheap Radio Shack meter -- even if repaired to work as well as they did when new, nobody wants to use them. They're relegated to being historical curiosities only.

Tektronix scopes from the dawn of the integrated circuit age have custom chips in them, with no readily available replacement sources except other old Tektronix scopes.  Too often, the same chips have failed in several scopes, so cannibalizing is not always practical. In any case, the older CRT scopes are big, heavy, and contain lethal voltages inside, so not every tinkerer would be well-advised to tear one open and fix it.  Most problems with a scope require at least a separate working scope to diagnose and repair.

Older analog oscilloscopes have one advantage over all but the very nicest and most expensive digital scopes:  They work well in X-Y mode.  Specifically, they continuously paint the X versus Y trace, with no interruptions for moving digital data around, no pauses to repaint the screen, no frame rate issues whatsoever.  There are a few cases where that can be very useful.  It can never quite be matched with a digital scope, but a few high-end units can sometimes come close enough for some practical purposes.

G0HZU:

--- Quote from: Fungus on May 22, 2024, 10:44:25 pm ---Some does, some doesn't.

A better question is: Is it worth buying old equipment second hand instead of buying modern gear?

--- End quote ---

The alternative is to rent new test gear instead of buying it.

For example, the (24 year old) Agilent E4440A PSA spectrum analyser is listed as obsolete by Keysight. To get close to the performance of its RF converter stages with anything new you would still have to pay about $60k or more. The alternative is to rent the new $60k+ analyser whenever the high performance is needed.

The rest of the time you could buy and use a low cost Siglent spectrum analyser if you don't want the baggage that comes with maintaining older test gear like an Agilent PSA analyser.

tggzzz:

--- Quote from: G0HZU on May 22, 2024, 11:11:04 pm ---For example, the (24 year old) Agilent E4440A PSA spectrum analyser is listed as obsolete by Keysight. To get close to the performance of its RF converter stages with anything new you would still have to pay about $60k or more. The alternative is to rent the new $60k+ analyser whenever the high performance is needed.

--- End quote ---

The last time I looked, a long time ago, a rule of thumb was that if you rented something for 10 months then you paid the same as if you had bought it. I.e. monthly rental cost was 10% of the purchase price.

Is that still true?

G0HZU:

--- Quote from: tggzzz on May 22, 2024, 11:17:34 pm ---
--- Quote from: G0HZU on May 22, 2024, 11:11:04 pm ---For example, the (24 year old) Agilent E4440A PSA spectrum analyser is listed as obsolete by Keysight. To get close to the performance of its RF converter stages with anything new you would still have to pay about $60k or more. The alternative is to rent the new $60k+ analyser whenever the high performance is needed.

--- End quote ---

The last time I looked, a long time ago, a rule of thumb was that if you rented something for 10 months then you paid the same as if you had bought it. I.e. monthly rental cost was 10% of the purchase price.

Is that still true?

--- End quote ---
It probably depends on the item. On my bench at work is a rented Keysight E5080B VNA (4 port 20GHz). I think I've had it about 5 months now. Fortunately, I have no idea how much it is costing a month. Over 5 months I doubt it will amount to 50% of the purchase price though.

pdenisowski:
I've spent the last 25+ years working for two of the biggest T&M instrument manufacturers.  Based on my experience, the short answer is "it depends"

Some instruments are obsoleted by changing technology:  no one needs instruments to test Token Ring, Frame Relay, ATM, AMPS, WiMAX, etc. anymore. 

And some instruments are effectively obsoleted by advancements in measurement technology:  I can still use a grid dip meter to tune an antenna, but there are MUCH better and cheaper ways to do this now (e.g. NanoVNA).

The only gray area is where older instruments can still perform ... roughly ... the same measurements.  I can use my analog HM407 scope for a lot of basic measurements, and for some of these it is not appreciably worse than a "modern" scope.  But speaking as a hobbyist, I feel that there are much better and much more cost-effective solutions than buying a decades-old analog scope.


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