In most cases, the RAM chip on a hard drive PCB is not a replaceable component, as it is integrated into the main controller chip. If the RAM chip is damaged or malfunctioning, the entire PCB will need to be replaced. It is important to ensure that the replacement PCB is an exact match for the original PCB, with the same model number and revision number, to ensure compatibility with the hard drive. Additionally, it is important to note that replacing the PCB should only be done by a professional data recovery technician or someone with experience in PCB repair, as this is a delicate and complex process that requires specialized tools and expertise.