Ahh, if you had said "attenuator compensation" I would have known exactly what you meant. Probe compensation is something totally different.
I'm still not seeing what they're doing. Other guesses are:
- Very tight tolerance/custom value fixed capacitors
- Laser trimmed capacitors (is that even possible?)
- Capacitors built into PCB layers, with vias drilled out to disable them
- "Capacitor DAC" with FETs switching in or out caps sized in powers of two (is that what those groups of 4 caps below the EE04AB chips are?
- Varicap didoe (seems like a bad idea)
- Digital compensation inside the ADC or ASIC for not quite perfectly compensated attenuator
- Analog compensation inside the amplifier ASIC
I'm presuming the EE04AB chips are amplifiers, and the EE05AF chips are ADCs. The big ASICs also have the national semiconductor logo, they probably did the entire ASIC set for this scope.
Tek REALLY needs to retire this archetecture. Other than the sample depth, it's just so unresponsive to the controls. I really hate it whenever I have to use one of these scopes. I press a button or turn a knob, and a second later it responds. The Agilent scopes, even old ones from the 90s, respond virtually instantly, Using a 14MHz CPU no less (in the 54622 that I opened up)!