The problem is that we noticed that the 90 degree pulse widths at all frequencies on the broad-band channel suddenly doubled (or more) in length. We no longer can achieve 50 ohm match anywhere along the tunable range of the probe (20 to 210 MHz), however it still tunes properly and we can continue to make measurements albeit with lower sensitivity. Pulse power is still fine as measured at the probe, about 250 watts at the lowest frequencies. An older 10mm backup probe is still yielding good 90s. Thus, we rule out the console. These probes are quite a work. We have opened this one up and looked for obvious problems but the matching capacitor network is buried.
Have you seen this happen on any of your own probes? Is there a straightforward fix?
Can you recommend any good probe shops, individuals, organizations (including Bruker!) that can put this thing back in shape for us?
Appreciate your help.
Chris Rithner
Chemistry Department
Colorado State University