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-NOTE: The 8MHz crystal is used for 4MHz operation of the
processor.
If 2MHz operation is desired, then a 4MHz
crystal (not supplied) should be used.
See the
Configuration section for details.
-ZI7. Recheck the circuits between the capacitor leads as in step
Zl and make sure they are still open circuits.
Note that
the capacitors which have been installed may cause the
ohmmeter needle to jump when first contact is made but the
indication should rapidly return to a high resistance.
-ZI8. Insert and solder the two 5-volt regulators (Q3 and Q4).
These parts will be marked "7805" or."340T-5".
Bend down
the three leads of the regulator 90 degrees so that the
leads go into the correct holes while the machine screw
holes line up.
Install the heat sink and regulator so that
the following sequence results from bottom to top: 6-32
machine screw head, PC board, heat sink, regulator, lock
washer, and nut.
Finally, make sure the leads do not touch
each other or the heat sinks and then tighten the machine
screw and solder the regulator leads.
-NOTE: Heat sink grease may be used though it is not
generally needed.
Tightening the bolts too tight can crack
the PC board.
-With the computer power off, plug the partially assembled
board into the motherboard.
Then turn on the power.
with a
DC volt meter check that both regulators are generating 5
volts output.
These voltages can be measured across the
pins of C22 and C23.
Wait a few minutes and measure again.
The regulators should not get very hot in this
configuration.
However, with all parts installed it is
normal for the regulator to feel quite hot to the touch.
Remember to turn off the power before removing the board.
-Z20. Construct a 16-pin DIP header with jumpers set up for a
starting address of E800 hex.
This is the standard HORIZON
starting address.
If some
other~tarting
address is
desired, change the header after G9mpleting the checkout
instructions.
See figure IZ for the details of the header
configuration.
Refer to the Assembly Information section
for header construction procedures.
Plug the completed
header into location 2E (the POJ ADDRESS socket) with the
correct orientation.
-Insert the 33 integrated circuits (all except the Z80A
chip).
Be sure that all IC's have pin I oriented to the
bottom left corner.
Do not insert any IC's inside the area
for the PROM option (outlined with a dashed line).
-Recheck the regulator output voltages as in step Z19.
13
-North Star Z80A PROCESSOR BOARD
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