Given the price tag, there is a limit to the amount of time you can spend on datasettes. Annoyingly, many of them come with minor issues like incorrect azimuth settings, dirty tape heads or defect drive belts, which mostly are easily fixed. But mostly isn’t the same as always.

What “working” should mean

In my perception, a datasette as a minimum should be able to –

• load from tape,
• save a program to an empty tape and load it again, and –
• reset the tape counter to 000 when the counter reset button is activated.

When testing the load function, I always use original games because they for the most part were recorded with factory azimuth settings. I like my test procedure to verify that the azimuth is set to factory default before listing the device.

A prefer to use test games that (a) have a short loading time and (b) display something useful on the screen during loading. At the moment, my go-to test game is Pitfall (Firebird version), which takes around 5 minutes to load and displays a nice hires picture if everyting works.

The main reason why I prefer short tapes is of course time. Further, Commodore’s datasettes were designed for short tapes. It may surprise many that the 60 and 90 minute tapes that most of used for “backup purposes” in fact were considered incompatible:

You may have a valid point in arguing that the use of short tapes in theory limits the validity of the test. I have no objection to that other than stating that I haven’t experienced any issues so far.

Further, I would like to note that there a games that just won’t load on a 1530. I have tested hundreds of original games, and I have seen cases of original games that didn’t load on a 1530 even with a new drive belt, and yet they but loaded perfectly fine on for example a Datamark datasette. Datamark made a range of clones, which were compatible with the C64 but were different mechanically.

Given the above, I don’t think you can conclude that a datasette doesn’t work, just because it doesn’t load longer tapes.