I’ve repaired a couple of Hitachi HA-5300 amplifiers so I’m familiar with how they work. Faults I’ve repaired on them include distorted sound, a failed speaker relay, and a blown bulb that illuminates the numbers around the volume control.
If you have one that needs repairing please contact me for a repair quote. Amplifiers can be sent to me or dropped off.
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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. 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.
If you need some electronics or a vintage amplifier repaired please contact me.