Wittman is right.
The 251 was a poor comparison to the 250.
Back in the early 80's I remember a particularly great sounding one owned by Jeff Porcaro that was parked at the studio I was working at. It sounded great, but had the annoying habit of making a very loud BANG from time to time. When I was assisting Greg Ladanyi on the Don Henley album, the machine went off once. Greg loved the sound and wanted to capture it. He wanted to use it as a primitive sampler and fly it into a song. At Greg's request I spent an evening trying to catch the sound on a 2 track. Predictably, it never made that sound when being recorded!