#892

Episode 892
$40 off eBay. Let's see how it works. Also a teardown at the end. 1960's technology still good
Specs:
230 MHz
10 Meg ohm input
4 pf input
+/-1V input
x1 attenuation
Be a Patron: / imsaiguy

[@Croccydile]

This is really cool to know for finding older ones on a budget. That gold packaged FET from 1968 must not have been cheap for the day.

[@gammaleader96]

Very nice look, I find the 93 Ohm coax that connects the probe to the box very interesting.

[@lupojacobo9892]

Thanks for sharing

[@jdmccorful]

Very nice, love the old style schematic. Thanks for the look.

[@OC35]

I love Tek circuit diagrams Remember when they used to add little cartoons ? i remember a circuit diagram that had a line going to a probe tip. An ant eater was drawn on it with its tongue out!

[@nickcaruso]

@@OC35 there’s a little guy riding a bicycle in some tek schematic someone showed me once, can’t remember what it was from tho

[@OC35]

@@nickcaruso Another one I remember is on a circuit that had a slow rise time pulse and a fast rise time pulse. They were marked by a tortoise and a jet fighter!

[@BryanByTheSea]

Very good score on Ebay, Congrats. Shudder what to think what it cost in it's day

[@IMSAIGuy]

I never had one at work. Too expensive.

[@andymouse]

So would this be used in say Phono stages of audio amps and very small signal work ?....cheers.

[@splitprissm9339]

This should be usable to explore a lot of the signals in a modern PC, without inevitably crashing it.

[@willthecat3861]

There's a lot of Tek FET probes being sold on epay ... but what you didn't mention... and what most people probably don't know is that the front end FET is blown in many/most of these probes... by careless people (the vendor?) having applied over-voltage to the probe tip. You can't get the FETs that TEK used anymore... so you can't fix these probes. Contrary to what you suggest, most people don't need these, and don't know how to properly use them either. If the probe isn't ruined already: it will soon be ruined, through careless use.

[@marka1986]

Might be fun to play with. Wouldn't pay any real money tho. If found 1 in with some junk would tinker with and try to see if could get a modern fet to work

[@splitprissm9339]

Standard 1:1/10:1 oscilloscope probe cannot even be trusted with a fast TTL signal, even it says a 10000 Mhz on the packaging. Of course, the secret alternative to active probes when dealing with that kind of circuitry is Z0 probes, which can be relatively trivially built or even integrated into a test setup, and can offer enough fidelity to be usable with 1GHz sampler - you just treat a piece of 50 or 93 ohm coax AND ITS TERMINATION AT THE SCOPE END as the lower leg of a voltage divider, and add an appropriate resistor (so, from a 50 Ohm tail, 470 ohm for a 10:1, 5000 ohm for 100:1, though 100:1 probes made that way tend to be imperfect without further compensation). 0603 resistors just tack soldered (properly!) in inline with a wire work fabulously for 10:1, it is a fragile but easily repaired setup. Don't split that off from the ground wire more than needed. Ahhhh - no more magnetic radiation pickup, no more capacitive surges, you can watch ECL and ACMOS circuitry do its thing gracefully.

[@splitprissm9339]

To wit, you haveth the scope beyond 50 Megacycles to a second, your probes passive and capacitive, they limeteth thee!