Keithley Model 1201 cathode follower probe

IMG 3273.jpg

An internet friend was restoring an HP 410B and dropped and broke the bezel :-(. We arranged to swap a replacement bezel from one of my HP 400H's for his Heathkit Tunnel Dipper. When I received the package with the dipper, I was delighted to find that he had included a surprise:

IMG 3277.jpg

 a Keithley Model 1201 cathode follower probe.

The internet doesn't seem to know anything about a Keithley Model 1201. I suspect it is the primordial hollow-state ancestor of the modern FET oscilloscope probe. 

I have yet to open it up. The probe body is nicely finished aluminum. The tail of the probe unscrews, though I haven't figured out how to detach the cable. It looks like the front will come off if I remove a couple of phillips head screws.

IMG 3275.jpg

It has an input impedance of 10 Megohms ...

IMG 3276.jpg

... shunted by 15 pF. The frequency response is 10 cps to 50 Mc. The accuracy spec for the 1 mV to 30 mV ranges is ±2% for 20 cps to 20 Mc, and ±3% for 15 cps to 50 Mc. For the 100 mV to 300 mV ranges the spec is ±2% for 20 cps to 10 Mc, ±3% for 15 cps to 20 Mc, and ±3 dB for 10 cps to 50 Mc.

IMG 3278.jpg

The probe has a UHF connector, presumably for the signal, ...

IMG 3279.jpg

... and what I think is a five-pin Cannon connector, presumably for power.

IMG 3280.jpg

I at first thought the probe went with some kind of RF millivoltmeter, but now I think the only missing piece is the power supply, and that the probe UHF connector was intended to mate with a Tek vacuum tube scope.

Does anyone have access to an old Keithley catalog?

© Steve Byan 2011-2019