That looks quite complicated compared to most senders on the market.
First, don't assume the unmarked IC is faulty. It could be, but they are very reliable.
Does it have power to all parts?
Is it producing any output at all?
If it produces an unmodulated carrier, the problem is the modulator not the PLL.
If you are sure the IC is at fault, trace the circuitry around and sketch a schematic, it doesn't look very complicated. Then compare the pin-out with known similar devices to find a match. Finally, see if the matched pins are on a device that suits the frequency and supply voltage. My first guess would be it is an LMX2332U or one of that family.
Brian.