MRAM

In the assembly/operation manual I just purchased there is a second schematic and wiring pictorial which addresses the shock hazard posed by the transformerless power supply.

In the assembly/operation manual I just purchased there is a second schematic and wiring pictorial which addresses the shock hazard posed by the transformerless power supply.

The chassi never was connected directly to the AC line. Rather there are bypass caps connected between the AC line (floating ground) and the chassi. This would allow a minor shock sensation but very limited current between the chassi and ground if plugged in backward.

However, the ground side of the RCA audio input jacks ARE connected to the AC line (floating ground) even though they are isolated from the chassi. This is where the shock hazard exists. When the AC cord is plugged in backward, the audio ground connection is connected directly to the AC hot.

The modified wiring disconnects the audio jack grounds from the AC line (floating ground) and connects them directly to the chassi. The audio ground return to the circuit uses the bypass cap connected between the AC line (floating ground) and the chassi. This restricts the 60 Hz AC current at the audio jack ground to a safe value. You may still feel a buzz but not enough current to electrocute.