Teletype 43K001/AAA, Руководство по ремонту

Страница: 53 / 82

MANUAL 525, 4-1
PART 4- CIRCUIT DESCRIPTION AND DIAGRAMS
CONTENTS
PAGE
A. GENERAL .....................
4-1
B. CIRCUIT DESCRIPTIONS ........ 4-1
43K101 KEYBOARD ............ 4-1
1. KEYSWITCHES AND SENSE
AMPLIFIERS ............... 4-1
2. KEYSWITCH LOGIC .........
4-2
3. CLOCK GENERATION AND
DRIVERS .................. 4-2
50K122 KEYBOARD ............ 4-2
1. KEYSWITCH LOGIC ......... 4-2
2. POWER ON RESET AND POWER
DISTRIBUTION ............. 4-2
43K001 RO KEYBOARD .......
4-2
1. SEND DATA OUTPUT ........
4-2
2. START CONTROL ........... 4-3
3. START LATCH ............. 4-3
4. CLOCK DIVIDER ............
4-3
5. ADDRESS COUNTER ........ 4-3
6. ROM- STORED DATA .......
4-3
c.
CIRCUIT DIAGRAMS ............
4-4
43K101/CAA AND CAB KEYBOARD
LOGIC ........................ 4-4
50Kl22/AAE AND AAF KEYBOARD
LOGIC ........................ 4-6
43K001/AAA KEYBOARD LOGIC .. 4-8
A. GENERAL
This part provides circuit descriptions and
combined schematic and troubleshooting circuit
diagrams for the 43 Basic KSR and RO keyboards.
Wave forms and voltage levels are shown on the
diagrams wherever possible to aid in trouble­
shooting and understanding of the circuit theory.
Circuit descriptions refer to coordinates on the
schematic, ie, (C2) to locate the circuit being
described.
For additional troubleshooting information
associated with these circuit drawings, refer to
PART 2- TROUBLESHOOTING which includes:
•
Troubleshooting charts.
•
Tables for dynamic and static VOM measure­
ments.
•
Illustrated layouts of circuits and physical loca-
tion of component and connector leads.
For part number identification of components
and unit codes shown on circuit diagrams refer to
PART 5- PARTS AND UNIT CODES.
Most numbers shown on various leads, compon­
ents and connectors on the circuit drawings are
. not actually marked on the equipment. They
are required for identification purposes when
referring to other parts of the manual.
The circuit diagrams in the part (with added
information on circuit layouts and physical
location of component leads from PART 2)
are also available as a separate package of dia­
grams with each major component on a single
sheet. The package of diagrams can be ordered
from Teletype Corporation as Manual 385, 43
Teleprinter Circuit Diagrams.
B. CIRCUIT DESCRIPTIONS
43K101 KEYBOARD
1. KEYSWITCHES AND SENSE AMPLIFIERS
Each capacitive keyswitch is connected to a single
input of a sense amplifier MLAl, MLA6 or
MLB4 (F2). These sense amplifier determines the
logic state applied to an input by comparing the
charging time of the keyswitch connected to
an
input to the charging time of a reference capacitor
(C2, ClO, or Cl5). Charging current for the sense
amplifiers
is
provided by reference resistors
(R6, R27 or R3).
The keyswitch logic transmit Data Enable (DE)
pulse which advance the sense amplifiers to
their keyswitch input and places the keyswitches
under test. When a DE pulse is received by the
sense amplifiers, they will respond by transmit­
ting two data bits if a keyswitch being sensed is
depressed. Data bit 1 (1st depression) will go high
when the keyswitch being sensed is first encount­
ered as "depressed". Data bit 2 (2nd depression)
will be high as long as the keyswitch continues to
be depressed.
This action continues until the sense
amplifiers have tested all inputs (21 keyswitches).
The keyswitch logic will then retransmit the 21
DE pulses plus 22 extra Data Enable pulses (while
internal functions are being performed) and the
cycle repeats.