Products > Test Equipment
cheap tek 500MHz passive probes on ebay. can they be used on any scope?
tggzzz:
--- Quote from: KE5FX on September 18, 2016, 07:56:50 am ---
--- Quote from: tggzzz on September 18, 2016, 07:32:16 am ---
--- Quote from: KE5FX on September 18, 2016, 06:19:32 am ---Watch out with the P6139A probe. Unless they've had their cables replaced, they had a whisker- or dendrite-growth problem in the cable that will short out the signal and drive you nuts. It can be cleared by running some current through the BNC connector but only temporarily. The only fix is to order a new cable from Tektronix, which I'm not sure you can still do.
--- End quote ---
Interesting!
Have you considered adding that to http://w140.com/tekwiki/wiki/p6139 ?
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Agreed, could be worthwhile when I have time to sign up for an account on there. It's not clear how widespread the problem is, or what serial #s are affected, but the problem is real enough. It's bitten me and at least a couple of other people who got their probes from different sources at different times. Very frustrating, because they are otherwise nice probes.
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It all sounds vaguely similar to the known problem with the delay line in HP1740A scopes. There, if you notice the risetime has risen from 3.5ns to 7ns, don't bother to tweak the controls as stated in the service manual. Instead, get your hand deep into the scope, and simply fondle, massage and squeeze the delay line.
David Hess:
--- Quote from: JPortici on September 19, 2016, 05:03:02 pm ---Thanks to tolerances, the capacitance is just enough so i can compensate the probe on a 7A22 (1M, 22pF)
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The 7A22 is 1M and 47pF. My common 100 MHz x1/x10 probes are only rated to about 33pF but barely make it to 47pF. My faster 250 MHz x10 probes do not have enough range to work with a 47pF input.
--- Quote ---Unfortunately i don't have faster plugins at the moment.. and IIRC they all are 50 ohm input.
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The fastest common high impedance amplifier is the 7A26 dual trace at 200 MHz. The single trace 7A16A is 225 MHz. The four trace 7A42 is 350 MHz.
Above 200 MHz, 50 ohm inputs are not that much of a disadvantage because the capacitance at the tip of a high impedance probe is a significant limitation at high frequencies. A x10 or x100 50 ohm probe has a higher input impedance at high frequencies although not at DC.
JPortici:
7A26, sorry! i tested with a 7A26
MarkL:
These are nice probes. I have a set of 4 myself.
The only thing I would add to what's already been said is that the tips are rather delicate. I've broken several. And not the metal tip itself. The plastic that holds the tip can crack or become loose and then the tip falls out. I think I was not being careful enough putting on the sprung hook or rotating the hook too much.
The tips alone are not replaceable. They come as a cartridge along with the input resistor and are expensive (qty 1 $45 at testpath.com, for example).
JPortici:
These probes are sold for 45. Grab some :D i will if there are more
(The seller contacted me before to ask how they were going. I'm not sure how to interpret that ::D)
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