Angular 4 Subscribing to observable is not updating after change

I have a service with an observable which is being subscribed to via a component. This seems to work as the subscriber is showing the initial value. I have another component which is then updating the observable however the new value does not get shown.

Service:

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of'; 

@Injectable()

export class BannerService {

    banners$: Observable<any[]> = Observable.of([]);

    getBanners(): Observable<any[]> {
        return this.banners$;
    }

    setBanners(banners: any[]): void {
        this.banners$ = Observable.of(banners);
    }

}

Component with subscriber:

import { Component, ViewEncapsulation, OnInit } from '@angular/core';

import { BannerService } from './../banner/banner.service';

@Component({
    selector: '.banner',
    templateUrl: './banner.component.html',
    styleUrls: ['./banner.component.sass'],
    encapsulation: ViewEncapsulation.None
})

export class BannerComponent implements OnInit {

    constructor(private bannerService: BannerService){}

    ngOnInit() {
        this.bannerService.banners$.subscribe(banners => {
            console.log(banners);
        });

    }
}

Component with setter:

import { Component, ViewEncapsulation, OnInit } from '@angular/core';

import { BannerService } from './../banner/banner.service';

@Component({
    selector: '.home-component',
    templateUrl: './home.component.html',
    styleUrls: ['./home.component.sass'],
    encapsulation: ViewEncapsulation.None
})

export class HomeComponent implements OnInit {

    data = {
        banners: [
            {
                title: 'Title 1',
                image: '../images/image1.jpg'
            },
            {
                title: 'Title 2',
                image: '../images/image2.jpg'
            },
            {
                title: 'Title 3',
                image: '../images/image3.jpg'
            }
        ]
    }

    constructor(private bannerService: BannerService){}

    ngOnInit(): void {
        this.bannerService.setBanners(this.data.banners);
    }

}

Any help would be really appreciated, I've tried a bunch of different things and can't get it working.