Recently mother obtained a second-hand off-brand compact camera about which the seller didn't know pretty much anything. Surprise-surprise, the camera is broken. Everything works, except the preview image (of bright day scene) is almost completely black, with only extreme highlights appearing as deep purples and violets. Shooting a photo takes a long time and still results in a photo that is completely black.
Thing is, mother bought a pretty much identical camera from a different seller a couple years ago, and it worked fine until last summer, when electronics (probably on power side; it was plagued with charging problems) died - the camera won't switch on. So, I can cannibalize it for spare parts and attempt to repair the new one - if I know what is to be replaced.
Can you help me identify this kind of fault, and possibly tell me how to approach repairing it?
Edit: The camera with these weird images is Vivitar ViviCam 5105s, the one with shot power is Premier DS-5080, but they seem like rebranding of the same product - slight differences in plastic case, different branding of the firmware but exactly the same construction details (button layout, battery, sockets layout, lens, menu layout, even the same plastic shield on the LCD screen.
Attaching one of the photos that didn't turn out all black. Unlike the photo, the preview on the screen does have some focus.
Photo of the camera LCD screen preview:
The scene it was taking:
I tried tuning the settings to max brightness (maximum ISO and EV), to no avail. Nothing apparent to obstruct the lens can be seen.