Hi-tech test gear.

The process of fixing my 40yr old amplifier continues:

I replaced the shorted power transistors and a dodgy looking capacitor. Then I built this ‘soft power on’ device to test it under power. Basically the power for the amp is all passed through an old filament light bulb, to limit the current so the amp should only just be ticking over.

It works! Switch on the amp and the bulb lights briefly as the power capacitors fill, but then goes out as the amp draws very little power on standby.

Next step is to meter the output, check it is biased correctly, and then we are good for a first full power switch on.