I’ve had this one since the 80’s:

I haven’t posted any recordings of it online although the YouTube demo of it by Nels Cline provides decent audio of the longest delay of 16 second repeats. The repeats are clear with a setting of about 1 second and get progressively lo-fi the longer the delay setting beyond 1 second.

There are two circuit boards inside stacked on top of each other and connected via a bus connector. The first board doesn’t have any trim pots and mostly covered with IC chips. I haven’t taken the second board out so I’m not sure if it has trim pots. Otherwise I’m not sure if it can be calibrated.