Commodore 64: No video or audio

[adamh9700]

I recently purchased a Commodore 64, with a monitor and drive. The seller told me everything works, but it wouldn't work for me. When it's all plugged in and turned on, the screen just stays grey. Shows nothing, has no audio. All the chips are secure and everything is soldered properly. Can't understand why it won't work. Any advice?

[adamh9700]

Photos of the machine.

[ChildOfCv]

What are the voltage readings from the power brick?

[carlsson]

That monitor has two inputs: one on the back side for luma + chroma (more or less S-video) and one on the front for composite. Both inputs have their own mono audio. You probably have a toggle button on the front panel or in the back to select input source. Depending on whether your cable has two or three RCA connectors, use the matching input and try to toggle it.