The block diagram of the power supply unit is shown
above. It adopts the self-excitation ON/ON control
method. First, the source supply is rectified through the
noise filter and converted into direct current. As the dc
current is applied to the switching transistor, it causes
the transistor to start repeating ON and OFF. After the
dc voltage is converted into high frequency pulse, it is
added to the primary side of the main transformer
which causes to induce voltage on the secondary side.
This high frequency pulse is then rectified and filtered to
obtain the dc voltage of +5 volts. For control of output
voltage, the output voltage is compared with the refer-
ence voltage and its error is detected in the control
section. While the switching transistor is in the OFF
cycle, it makes the photo cuppler PC1 active by the
detecting signal of the control section for given period.
By adjusting control current of the drive circuit, it makes
the out put stabilized.
Dust deposit inside the power supply unit may becomes
the cause for overheat as it prevent heat dispersion,
which results in damage in component. Stains on the
fuse contact and connector contact may lead to contact
failure. So, it has to be cleaned using soft cloth dam-
pened with alcohol or dry soft cloth.
5-4. Problem determination and sequence
Follow the next procedure to find the cause of trouble.
(1) Avoid removing the board to check. But visually
observe the board to check for open circuit line,
burnt resistor, fuse, and semiconductor chips in the
(2) If a defective item were found, it has to be replaced
with the new one. But. care must also taken as
there are possible defects in mUltiple number of
The MZ-1 P16 is the external installation 4-color plot
printer designed for use with the MZ-800 series person-
al computer. It can be fixed on the MZ-800 when the
table is used.
1, Black; 2, Blue; 3,
Green; 4, Red
10 characters average
+5 V supplied from the
MZ-800 via the DC jack
162(W) x 133(D) x 59(H),
1 kg (MZ-1P16)
Roll paper (1), ball point pen (one
each of black, blue, green, red).
paper holder (one each on side),
paper shaft (1), paper guide (1)
0 to +35 centigrades
-20 to +70 centigrades