Derogatory term for electronic device

Solution 1:

Piece of junk refers to something that is cheap, shoddy, or worthless. It can be used as an oject as in "This piece of junk won't boot." or a modiying adjective as in "This piece-of-junk computer won't boot" (with or without hyphens).

Related adjectives can be used with the name of the device. These include:

"Junky", "shoddy", "trashy", "lousy", "worthless", "crappy" (oh, and, of course, "shitty").

Boat Anchor which merely means the device is only suitable for that purpose. "This computer has become a boat anchor" (Urban Dictionary, definitions 2 and 3, Ham.net shows the term used in practice.)

Doorstop similar to "boat anchor". "This computer only works as a door stop now."

Junk Box No longer suitable for anything except to be cannibalized for spare parts. (See wikipedia.) Usually this refers to just the parts themselves, already disassembled and collected into a box. But it parallels your German reference, so I thought it was worth adding.

We also refer to some things as "hangar queens", which is alludes to aircraft that spend more time in repair than they do in service. Any products that can't get through the production process may be relegated to being hangar queens, with hopes that someone will eventually figure out how to repair them.

Solution 2:

Contraption (often paired as infernal contraption) refers to any mechanical or electronic device for which the author has some contempt.

Gizmo can similarly be employed to mock some needless or useless technological contrivance, but it is not inherently negative. I can call something a gizmo to suggest I am overwhelmed by its complexity, or simply because I don't remember its name. Similarly, other generic terms like gadget or widget (for a part of a larger machine or device) are not inherently negative.

There are a variety of ways to disrespect a car or other large mechanical machine: jalopy, rust bucket, beater, or clunker.

There are also words and phrases for televisions, but these emphasize dislike for the medium of television itself as represented by the device, not the device itself: idiot box and boob tube. You could say I'm spending a mindless Saturday night in front of the boob tube, but you wouldn't say I hate my old boob tube, I need to get it replaced.

Solution 3:

Paper weight Implies that it is good for nothing other than holding paper in place.

Solution 4:

While often used to describe, as you say, jalopies, bucket of bolts can also be used to refer to machinery:

(idiomatic) A piece of machinery that is not worth more than its scrap value, often of old cars.

Other candidates that you can consider are contraption and its synonyms. However, they are not necessarily uncomplimentary. Most people would probably use something along the lines of junk or piece of [x] where x can be replaced with junk, crap, shit, etc.