TM 11-6625-3145-14
Theory of Operation-318/338 Service
MAINFRAME
ROM/THRESHOLD BOARD (A05)
The ROM/Threshold board is installed into J5 on the Mother board.
ROM. Six 16K X 8-bit mask ROMs and one 8K X 8-bit EPROM are mounted on the ROM/Threshold board. Part of the
ROMs are configured into four pages, since only 64K bytes of the 112Kbyte total can be addressed at a time.
Threshold Circuit. The threshold circuit contains two latching digital-to-analog converters. This circuit provides three
kinds of threshold levels: V1, V2, and V3 {(V1 +V2)/2} for both parallel and serial probes.
MPU/DISPLAY BOARD (A06)
The MPU board is plugged into the J06 card-edge connector on the Mother board. The MPU board contains a Z-80A
microprocessor, RAMs, a display controller, a character ROM, bus buffers, key control logic, and oscillators for the MPU
and TV timings.
Microprocessor. A Z-80A microprocessor controls all operations for diagnostics and data acquisition.
RAMs. Two 1K X 8-bit static RAMs are used by the MPU to store data and flags.
Display Controller and Character ROM. This integrated circuit, developed by Sony/Tektronix, controls the 318/338
display data stored in the display RAM. The display controller decodes control codes for inverse video, blinking, other
special display codes, and letter codes by referring to the character ROM. It then generates control signals for the CRT.
Bus Buffer. All address buses and data buses are buffered to provide sufficient fan-out to drive several boards connected
to the bus through the Mother board.
Key Control Logic. Key signals from the keyboard are encoded by a priority encoder and are sent to the MPU as a key
code with an interrupt. All keys (except the STOP key) can be masked by the MPU with the keyboard mask bit.
MOTHER BOARD (A08)
The Mother board provides interconnection for boards A01 through A07 through connectors J1 to J7. In addition, this
board routes power to all boards and has connectors for the keyboard and the CRT boards.
KEYBOARD (A09)
The keyboard serves as the operator’s interface. The operator selects the menu to be displayed and sets up the
instrument from the keyboard. All functions of the 318/338 can be controlled from this keyboard in the local mode.
Pressing any key will cause an interrupt to be sent to the MPU, along with the key code corresponding to the key pressed.
CRT BOARD (A10)
CRT. The CRT is a four-inch raster-scan type.
CRT Circuit. The CRT circuit provides z-axis voltage and the horizontal and vertical deflection-current outputs that are
used for the CRT. A flyback transformer in the horizontal deflection circuit provides the high voltage and other CRT
electrode voltages.
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Summary of Contents for 318
Page 119: ...318 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 182: ...338 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 253: ...318 ___________________ TROUBLESHOOTING TREES ...
Page 344: ...338 TROUBLESHOOTING TREES ...
Page 517: ...TM 11 6625 3145 14 318 338 4434 923 318 Block Diagram ...
Page 518: ...TM 11 6625 3145 14 318 338 4434 924 338 Block Diagram ...
Page 519: ...TM 11 6625 3145 14 318 338 4434 925 318 Acquisition Module Wiring Diagram ...
Page 520: ...TM 11 6625 3145 14 318 338 4434 926 318 338 Mainframe Wiring Diagram ...
Page 521: ...TM 11 6625 3145 14 318 338 4434 926 338 Acquisition Module Wiring Diagram ...
Page 522: ...TM 11 6625 3145 14 318 338 4434 928 Figure 9 1 318 A01 Input A Board Component Locations ...
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Page 528: ...TM 11 6625 3145 14 Figure 9 3 318 338 A03 ACQ Control Board Component Locations ...
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Page 542: ...TM 11 6625 3145 14 Figure 9 8 318 338 A10 CRT Board Component Locations ...
Page 544: ...TM 11 6625 3145 14 Figure 9 9 318 338 A11 Inverter Board component Locations ...
Page 546: ...TM 11 6625 3145 14 Figure 9 10 318 338 A12 Regulator Board Component Locations ...
Page 551: ...TM 11 6625 3145 14 Figure 9 12 338 A01 Input A Board Component Locations ...
Page 553: ...TM 11 6625 3145 14 318 338 SERVICE ...
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Page 555: ...PIN 058584 ...