Hi,
I have installed an Amazon Echo Dot into this boombox which I think is a good addition to the already great device.
One way of making these vintage units still useful today
You can see my video here:
I use my Dot in the garden and it sounds just fine as it is. I also have a battery dock which is like a power bank so it's portable wherever you go as long as you have WiFi.I googled it and found your video.
It reminds me that I have a similar Hitachi boombox in my loft. I may get it out to use in the garden in the summer (if we have one). I will probably just plug into the Aux In though!