A vintage Pioneer SX-450 receiver that had a loud hum on the output.
This is a receiver from the days of wooden end cheeks and brushed aluminum front panels, something manufacturers don’t do any longer.
After a bit of probing around the circuit board with an oscilloscope I found a failed capacitor in one of the power supplies that was allowing 50Hz from the mains to get onto a power rail. That affected the amplifier that put it out to the speakers as an annoying hum.
In the world of power amplifiers it’s nothing special at only 15W per channel, but it’s well made and looks far better than a lot of modern HiFi.
It doesn’t sound too bad either from its proper transistor output stage.
If need your modern or vintage amplifier repaired please email me with any photos and model numbers to: firstname.lastname@example.org
Below is a video look at the unit, showing both inside and out that I’ve put on the Orangevalley Systems YouTube channel.
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