Service
Model
1332A
8-17. SEMICONDUCTOR REMOVAL AND REPLACE-
MENT.
Figure 8-1 is included to help identify the
leads on the common shapes and sizes of semicon-
ductor devices. When removing a semiconductor, use
long-nosed pliers as a heat sink between the device
and the soldering iron. When replacing a semiconduc-
tor, ensure sufficient lead length to dissipate the sol-
dering heat by using the same length of exposed lead
as used for the original part.
8-18.
CIRCUIT BOARDS.
8-19. The following paragraphs provide information
regarding servicing procedures for etched circuit
boards.
8-20. BOARD CONNECTIONS.
Square-pin connectors
are identified on circuit boards by the color code of the
connecting wire. Connector pins on plugs and jacks
are identified by either a numeral or a letter. The
letters
G,
I, 0, and
Q
have been omitted. Table 8-1
shows the types of board connections used in the
instrument.
8-21. SERVICING ETCHED CIRCUIT BOARDS.
This
instrument uses etched circuit boards with
plated-
through component holes. This allows components to
be removed or replaced by unsoldering from either
side of the board. When removing large components,
such as potentiometers, rotate the soldering iron tip
from lead to lead while applying pressure to the part
to lift it from the board.
HP
Service Note M-20E
contains additional information on repair of etched
circuit boards.
8-22. HEAT SINKS.
The heat sinks used on this instru-
ment are all of the friction type. They can be removed
by carefully pulling them off. When reinstalling, sup-
port the bottom of the transistor before pushing the
heat sink on. Transistor damage may result if the
transistor leads are bent.
8-23.
TROUBLESHOOTING.
WARNING
Read the Safety Summary at the front
of this manual before troubleshooting the
instrument.
8-24. The most important prerequisite for successful
troubleshooting is understanding how the instrument
is designed to operate and correct use of front-panel
controls. Suspected malfunctions may be caused by
improper control settings or circuit connections.
Before doing the test and/or troubleshooting proce-
dures, read Section
I11 (Operation) for an explanation
of controls and connectors and general operating
considerations.
8-25. If trouble is suspected, visually inspect the
instrument. Look for loose or burned components that
might suggest a source of trouble. Check to see that
all circuit board connections are making good contact.
If no obvious trouble is found, check the power supply
voltages in the unit. Prior to any extensive trouble-
shooting, check the external power sources also.
8-26. TROUBLESHOOTING THE LOW-VOLTAGE
POWER SUPPLY.
If the supply is completely in-
operative, inspect the line fuse located on the rear of
the instrument. If the line fuse is open, the power
lamps will not be lit. Check input voltage source for
proper voltage.
8-27. The voltage from each secondary winding of
input transformer
TI is rectified by a full-wave bridge
rectifier and filtered by
a
capacitor (the +lo0
V
supply
is filtered by two capacitors). In the event of diode
failure, the supply voltage will vary considerably
from the design value and filtering will be severely
affected. Loss of
a
filter capacitor will affect the volt-
age and result in excess ripple at the series regulator
input.
8-28. Fuses and adjustments for the dc voltages are
located on the mother board, Al. The fuses are con-
nected in series with the regulator transistors. In case
a fuse is open, check the series regulator and driver
transistors.
8-29. No output voltage may be the result of an open
fuse open series regulator transistor, or loss of the
+I00
V
reference voltage. When all supplies are in-
operative, check the
+I00
V
power supply first.
8-30. Too high a voltage may be caused by a shorted
series regulator transistor, shorted driver transistor,
+lo0
V
reference voltage out of regulation, or a defec-
tive sensor amplifier. If the *15
V
supplies are low,
check the output of the
+lo0
V
supply.
8-31. If the
+loo-volt supply exceeds the acceptable
range
(+I00
+5
V
-0
V),
check the resistor divider net-
work
AlR61 and AlR62 for proper values. Check for
low input line voltage.
Contact with the high-voltage power sup-
ply voltage can result in injury or death.
8-32. TROUBLESHOOTING THE HIGH-VOLTAGE
POWER SUPPLY.
Malfunction of the high-voltage
power supply will usually result in loss of beam spot
or unstable intensity. Troubleshooting may be accom-
plished by resistance checks of the high-voltage oscil-
lator, high-voltage transformer, and regulator circuits.
In the event of complete failure, check fuse
AlF4. If
fuse is all right, check -15
V
supply. Failure of the
Scans by ArtekMedia © 2008
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