question about oscilloscope probe

[lokeycmos]

i picked up a scope probe today at a flea market. it is a 100mhz switchable between x1 and x10 with a compensation trimmer built in. I have attached some pictures. before I got this probe I was simply using a piece of coax stripped back for my probe with a ground clip soldered on. when I connect my function generator to the scope using my homemade probe and set to 10v/division I get a proper square wave signal. but when I connected the new probe set to x1, the only way I get a reading on the scope with everything else the same is to turn it all the way down to .01v/division. expectedly its is even less when I switch to x10. so my question is, if it is at x1, why is it so attenuated compared to just a straight piece of coax? is it possible I got a bad probe? ty

one more thing, why are the edges so round with x1?

 

[lokeycmos]

more pics of probe

 

[ronsimpson]

Is your scope 1meg or 50 ohms? Input impedance

 

[crutschow]

Looks like you may have a bad probe. Apparently all your are seeing is the signal through the compensation capacitance.

Measure the resistance from the tip to output. It should be less than an ohm on the X1 setting and around 9 megohm on the X10 setting.

 

[JimB]

I would say that something is open circuit in the probe.

Is the hook which you have on the probe tip making proper contact with the probe body?

Is the probe used or is it new?
If it is used, I think that you may have a dud.

JimB

 

[ronv]

Looks like 1 meg and 47pf.

 

[Dean Huster]

Measure the resistance from the tip to output. It should be less than an ohm on the X1 setting and around 9 megohm on the X10 setting.

Not necessarily true. I think that most of us consider Tektronix to be the historical acme of oscilloscopes and probes. Because Tek uses resistance wire as the center conductor of their probes (even the 1X variety), don't expect less than one ohm tip to BNC. You might find more like 100 ohms. This resistance is negligible compared to the 1M ohm scope input impedance, but does wonders for making a probe with better HF response and step response.

It does sound like you have an open probe, but it's likely not the center conductor if it works in the 10X position -- it may be the switch. But taking the probe apart is likely to result in total disaster as many probes are now made modular and not designed for repair as we normally define repair. The Tek P61xx-series probes are modular and designed to be repaired by replacing either the probe head, the cable or the compensation box.

Pomona is known for good products and they're not a fly-by-night company by any means, making some of the highest-quality adaptors and other products that are available on the market. Contact them. They may prove to be more help than you may realize even if you didn't buy your probe directly from them.

 

[lokeycmos]

thanks for the help guys! the probe does work. for some reason the component lead clip was not making connection to the probe. when I switched tips it works great!

 

[crutschow]

thanks for the help guys! the probe does work. for some reason the component lead clip was not making connection to the probe. when I switched tips it works great!

Sometimes you have to firmly push the tip onto the probe to make contact.

 

[JimB]

As I suspected.
The Hook does not appear to be sitting correctly on the probe.

It is difficult to tell from the picture, but is item 4 of the "Probe Accessories" fitted to the body of the probe while you are trying to fit the hook?

Or, looking at the picture by the list, should item 3 be removed from the probe before fitting the hook?

JimB