Power Board Assembly - North Star MDS-A Manual

POWER BOARD ASSEMBLY
There are three different ways that power can be supplied
to a disk drive.
a. Direct hook-up of regulated +5 volts and +12 volts from an
existing regulated power supply. In this case the Power PC
Board is not used and the four conductor power cable should be
connected directly to the power plug as described in Step 5
below. The other end of the power cable should be connected
to the corresponding outputs of the regulating power supply.
b. Use the Power PC Board to regulate power from an existing
unregulated power supply. Under most circumstances the power
supplies in the following computers provide adequate power to
supply one drive: IMSAI 1-8080, Altair 8000b, and POLY-88. In
general, compare the disk drive power requirements against the
power supply capacity to see if this arrangement will work.
If this power supply option is to be used then follow the
instructions below starting at step 1.
c. Use the North Star Power Supply option (MDS-PS). The MDS-PS
provides all the comp6nents needed to obtain unregulated power
from a 115 volt AC line. Some of the MDS-PS parts mount on
the Power PC Board and some mount to the North Star MICRO-DISK
Cabinet (MDS-CAB) or elsewhere. If this option is used then
start assembly with Step 1 below and continue with the MDS-PS
assembly instructions.
The silk screen legend is on the component side of the PC board
and the traces are on the solder side.
1. Install and solder the two 1% precision resistors in the
locations indicated by the silk screen legend.
Rl 232 ohms
R2 1.96 K
2. Bolt the +5 .volt regulator (7805 or 340T-5) to the inside of
the 295-2 heat sink so that the following sequence results
from outside in: 6-32 bolt head, heat sink, regulator, lock
washer, and nut. The regulator leads should point the same
direction as the heat sink mounting posts.
3. Install the regulator heat sink assembly by inserting the
regulator leads in the correct holes on the PC board and then
inserting the heat sink mounting posts in their holes. Now
solder the regulator leads-.
The heat sink mounting holes may require a slight amount of
reaming. Do not over ream as the heat sink should fit snugly
into the holes for mechanical support.
North Star MICRO-DISK System 20