The Counter Logic Board and LED Display Driver board are substantially different. The Corsair II manual has the correct new schematics but the text errs substantially by describing the Corsair I circuitry.
The Corsair I stock 9Mhz filter is 2.4Khz 4-pole while the Corsair II stock filter is 2.4Khz 8-pole. The Corsair II also includes a 2-pole roofing filter on the mixer board before the 2.4Khz filter.
Audio Bandpass Filter
The Corsair II introduced a variable audio bandpass filter in lieu of the iconic orange dot Ten-Tec insignia on the Corsair I.
The Corsair II introduced an internal cw keyer, with memory capability
The Corsair II added a Noise Blanker Width control
The Corsair I used 4 discrete Schottky diodes in the mixer while the Corsair II used 4 monolithic Schottky diodes in the mixer.
The Corsair I spot button turns on a sine wave oscillator to inject an audible sidetone (nominally 750hz) that's mixed with the receiver audio so the target rx signal can be tuned to have the same tone as the sidetone to accomplish zero beat. The Corsair II spot button shifts the receive frequency downward by an offset equal to the sidetone frequency (nominally 750hz) so the target rx signal can be tuned for null to accomplish zero beat.