7
place so the ribbon is routed inside the tensioner and looped around the guides
on both sides of the platten. The ribbon is self-reversing so it doesn't matter
which spool is placed where. After installing the ribbon, be sure that each
ribbon spool will turn freely on its respective shaft. If a spool is excessively
tight on a shaft sanding the shaft slightly with sandpaper should help. If the
binding is being caused by the two springs on the spindle that hold the spool in
place a small washer can be placed between the bottom of the spindle and the
mechanism that it is attached to. This will allow the spool to ride lower on the
spindle.
You are now in a position to test and set the line length and print
intensity adjustments on the printer. By having everything exposed as you do now,
adjustments and troubleshooting will be considerably easier. Once the unit has
been calibrated and thoroughly tested, as described later in the instructions,
the print mechanism can be disconnected and reinstalled and secured on the top of
the printer chassis using #6-32 nuts and lockwashers. All of the wires for the
print mechanism are then run thru the large bushing on the top of the printer
chassis. The I/0 cable feeding the printer is also run out of this large bushing
so that the bottom of the printer may be closed with the perforated cover
supplied with the kit. The cover is secured with #6-32 screws and tinnerman nuts
which are also supplied with the kit. The four rubber feet should be attached to
the outside of the cover about 1" in from each corner.
Wiring the Printer's Input Data Connector
The actual ASCII data fed to the printer is input thru connector J4 on the
PR-40A board. In order to test and set the calibration controls on the printer,
it will be necessary to load a diagnostic program into your computer system to
feed data to the printer. The program should feed the printer continual,
printable ASCII data. This will force the printer to print full 40 character
lines which are necessary to set the line length trimmer resistor, R17 for
symmetrical margins. Trimmer resistor R25 sets the print intensity and may be
adjusted when printing any line length.
If you are using the PR-40 printer with the SWTPC 6800 Computer System you
should use the PRNTST-1 diagnostic contained within this instruction set,
otherwise you will need to write a program for your own specific computer system
which performs similar functions. You may even feed the printer directly from an
ASCII keyboard if you can live with not being able to read the line until a
carriage return is entered. The keyboard must output a negative going
"keypressed" strobe for direct compatibility with the PR-40 Printer.
The data connections to J4 on the PR-40A board should be made as follows:
J4 Pin # Data
Connection
1 ground
2
"data accepted" output - from printer
3
"data ready" from computer
4 ground
5
ASCII bit 5
6
ASCII bit 6
7 no
connection
8
ASCII bit 3
9
ASCII bit 4