I wonder if anyone is using iOS (iPad, iPhone, etc.) apps for signal generator and scope functions in aligning and troubleshooting their tape decks. Are they useful, a waste of time and money, something in between? After more than a 50-year hiatus from hands-on work with electronics, my interest has been "recharged" by the necessity to deal with some new-old recorders I've acquired and plan to acquire. So, I neither own any test equipment, beyond a multimeter, nor am I in a position to begin buying it in my old age.