If I recall there are 2 MMIC chips, the large one you mention (U105) and a smaller black plastic one (U100) to the left of the big one and to the right of the 15 Mhz crystal filter. Just above the chips you will see 2 inductors marked L101 and L102 that supply the d.c. power to the chips. The larger U105 chip on the right feeds its output through the PLP-18-11 low pass filter to the 15 Mhz output connector. If you don’t need 15 Mhz,you may be able to remove U105 rather than try to replace it and connect the output of the oscillator through a capacitor to the input of the LPF and use the 15 Mhz SMA connector as a 10 Mhz sine output. I haven’t tried this but it might work. -Arthur