This old Hitachi HA-5300 needed a repair as it had distortion on one of the channels.
An interesting old design as it uses a class E amplifier stage that Hitachi call Dynaharmony. I think back when this was on sale a lot of amplifier manufacturers were experimenting with different types of output stage and this is one of them.
The Hitachi amplifier uses proper power transistors for the output stage rather than an obsolete STK module that ended up in most amps of the time.
Some components had drifted out of value causing distortion on the output so were replaced along with resetting the output stage idle current (bias).
The oscilloscope image below shows the output distortion at 1KHz. This is classic amplifier crossover distortion.
I’ve put a repair video on my YouTube channel along with other amplifiers videos. Take a look and please subscribe to the channel.
If you need some electronics or HiFi repaired please contact me.