Professional tape delay units are great fun, but often expensive. You’d think that with so many derelict cassette decks filling the world’s dumpsters someone must have figured out a way to make a cheap tape delay… not only in the interest of saving money (sometimes quality is worth paying for) but also in the interest of re-using otherwise wasted resources.
Forosdeelectronica forum user [Dano] has made just such a device from used cassette decks and miscellaneous parts (translated). First he investigated the operation of the playback, erase, and record mechanisms and broke out the tape heads. The playback head is on a plastic rail so that the delay time can be changed, while the record head is fixed. [Dano] encountered some difficulties in ensuring good quality for the recording and erasure, which is an important consideration when working with magnetic tape.