dumb question #53647 - scope probes

I don't know the answer to this one, but I'd think a little bitty tweaker could fit through that hole - like one of those plastic TV tools.

That's what makes it specific to the TDS300 (and possibly others - I've seen that type of thing before), is that there's a contact ring around the outside of the BNC on the scope, that that pin contacts, and tells the scope "I'm a 10X probe."

Hope This Helps! Rich

There should be a compensation adjustment screw under that tiny hole in the "box" at the base, adjustable with the usual tweaker. If it's missing, that could be why it was on eBay...

The spring-loaded pin on the connector allows the probe to tell the scope what its impedance ratio is, i.e., 10:1. IIRC, you can't "lie" to the TDS400 scopes by manually setting the ratio for a given channel; they "know" based on the coding that comes back from the probe via that pin.

The coding pin fits into a recessed collar around the base of the BNC connection on the scope. The limitation on "for use only with" *may* be because the depth of the pin interferes with connecting the probe to some scopes.

Rich Webb wrote in news: snipped-for-privacy@4ax.com:

what's the charts on TEK's website say for that model probe? There may be a bandwidth limitation.

The required tweaker may not be the usual straight screwdriver-style bit;it may be one of those ultra-miniature square drive types.

The TDS scope BNCs also have probe power contacts for active probes,I believe.

Sounds like a perfect description of this probe's adjustment! I guess I can't use the tiny steel watchmaker's screwdrivers I have for this purpose as they'll introduce their own capacitance. What is the proper tool to use for this?

Hi,

next in this series of Dumb Questions:

I've been offered a 1000Mz FET active probe for my 350Mhz analogue Tek scope. I like the super-low loading feature of these probes for delicate RF circuits, but will I have a problem compensating it? The probe's input capacitance is just under 2pf whereas the scope's is

I have a 6139 probe which looks similar, only has a single pin to notify the scope of 10:1.

The compensation adjustment is a long way inside - only just visible and requires a crosspoint (philips) tools.

---Paul

Paul Burridge wrote:

Definitely no power connection; not sure about the plug. The sockets on the scope are the usual bnc female type.

The first question is: Does your scope have a power connector for the probe, and does it match the plug on the probe?

The second question: Does your scope have the ability to switch its input impedance from 1Mohm to 50ohm? Active probes usually expect a

Regards, Allan

The FET probe is useless without power, and the only source I ever found for the power connected was from a junked TEK scope.

Tek makes FET probe power supplies too (1101A is one for the P6201 probes).

no, in fact it sounds like the exact setup i have ! :) i have a set of P6201 active fet probe kit. to be used on my Tek 350 Mhz scope. it works very good. i have a 1.5 Pf tip for mine. :)

you don't have a 485 ? the power is not in the bnc., is little half moon looking thing. small round hole with a half moon key.

The scope in question is the 2465A; it has no such facility, I'm afraid...

The company I worked for wouldn't buy it, and they had plenty of junk scopes. They even swiped a few from the rear of working scopes that were too far away from the BNC input connector to use the FET probe.

If you have a phillips jeweler's screwdriver, I'd say, go ahead and try it. The adjustment screw on those things is _supposed to be_ at ground potential. Give it a shot, and if, when you pull the tool out, the waveform changes, then stick the tool back in, and overadjust it the other way - it may take a few minutes to get it spot-on, but it could be both instructive and possibly, fun. :-)

Good Luck! Rich