Commodore CASSIOPEI, User Manual

Page: 61 / 76

Fortunately, you are not alone. And in practice there isn't a special calibration tape required. All
you need is a tape with a signal on it written in a time where the calibration was still OK. Or written
on another device that has a good/perfect alignment. The best you could do is using the tape you
intend to load, that way you would get optimal alignment for that tape, which could be better (for
that situation) then the perfect azimuth. Regarding a tape to use to adjust your tapehead to the
perfect azimuth, you can use most commercial games tapes. Because these tapes were written on
machines with a good/perfect head alignment.
On the right, a screenshot is shown of a program for
the C64, it is called “recorder justage” (it can be
found on the internet on many places, for instance on
CommodoreScenDataBase (CSDB.dk)). This tool is
perhaps the most used tool for tape adjustment,
simply because it was released for free in a
magazine, the same program can be found under
various names as it has been slightly modified by
some or translated. But the essence of all is the same,
make sure the shown lines are as thin/clear as
possible. The location of the lines may vary,
depending on the type speedloaders the tape uses.
Although it is not required to use a tape that has a
speed loader, in fact the actual data on the tape doesn't really matter, as long as it is there long
enough for you to calibrate the tapeheads. If the tape is too short, you'll be constantly rewinding the
tape, which could be a bit unpractical.
The story behind the program “recorder justage” (according to people on CSDB) goes as follows:
Recorder justage by Harald Diebek, from Input64 06/1985.
Harald owned a computer store, one of the top seller was the C64. He had a lot of returns and
complaints from customers who had problems loading tapes (which they obviously copied from a
neighbour or friend). Harald got tired of all the complaints and grabbed a "C64 intern" and coded
this little tool. Some time later he eventually sold it to the "heise verlag" for publishing on "input
64" for 3000DM. For that money he bought himself a PC-XT. Harald never had his own c64 (at
home that is), and he never programmed any c64 stuff again.
How to use the program? All you need to do is play the tape back and observe the signals as a
function of the time (you could call it a spectrum of the audio signal or you could call it a waterfall
display). But what's important is that the screen showing the signals must show lines that are as
sharp as possible which is only the case when head alignment is optimal. Insert a tape into the
datasette, fully rewind it and press play, then insert the screwdriver. Therefore watch the screen
while gently tightening the screw by turning the screwdriver clock wise until the signals get worse.
Mark this position. Turn your screwdriver counter clockwise until the signals get better and keep
turning until they get worse. Mark this position, now turn your screwdriver to the position exactly
in the middle of the two marked points. This should be the most optimal position. Remove the
screwdriver and stop the tape, you are ready to load.
2019-10-27 Page 61 of 76 CASSIOPEI v2.0