Dragon disk drive RPM checker

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bluearcus
Posts: 142
Joined: Wed Sep 07, 2016 4:45 pm

Dragon disk drive RPM checker

Post by bluearcus »

Here's a Dragon-ised version of Robert Gault's disk drive RPM checker that I posted on FB some time ago.

Use is obvious... load using a working drive, Gotek or drivewire, and then run with the drive for testing attached and a disk inserted.

Note... Dragons 32s have two different possible main crystal values, 14.318MHz and 14.218MHz. Divided by 16 this gives 0.89 and 0.88MHz main clock frequencies respectively. On a 32, examine the crystal and then ensure the correct CRYSTAL= assignment is comment/uncommented in the basic program, so your RPM reading will be as accurate as possible. 64s all use 14.218, so configure for 0.88Mhz.

Dragon drives should be running at 300rpm, like most other 5.25" non HighDensity floppy setups, but old drives often tend to run slow. This will indicate if you need to do some cleaning and lubrication, or adjust the RPM potentiometer on the drive itself.

Alternative approaches - use a 50Hz strobe light, if the drive has suitable markings for this. Or scope the index signal pin on the drive with it running and a disk inserted and measure the frequency from there.

Thanks to Robert Gault for the original CoCo tool which was easy to port.
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DRAGRPM.DSK
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