Yeah if you’re down to put the effort into fault tracing, you’ll need an oscope. Something like this: ebay.io/m/PDLGdu will work fine.

It will take some time, but if you’re lucky you’ll find it’s just a capacitor that you can replace cheaply. If you’re unlucky you might find that it’s a faulty IC, in which case you might have to replace an entire circuit board from a donor unit anyway.