How to make checked box value as true in reactive forms using angular8

I have binded the checkbox values dynamically. So now based on check and uncheck, i need to pass the same array of data, with values as true/ false.. But now, even the value is checked it is showing false only and based on check and uncheck values, if i uncheck anyone of the checkbox, the select/Unselect is still checked.

DEMO: DEMO

TS:

 checkAll(ev) {
    if (!this.all) {
      this.PrintList.forEach(x => x.value =  true)
      this.isAllChecked()
    } else {
      this.PrintList.forEach(x => x.value =  false)
      this.isAllChecked()
    }
  }

isAllChecked() {
    this.all = !this.all
}

onChange(event, item) {
 if(event){
    this.printLists.push(item);
    } else {
      this.printLists.splice(this.printLists.indexOf(item), 1)
    }
  }