TM 11-6625-3145-14
Theory of Operation-318/338 Service
+ 5 Volt Supply. The + 5 volt regulator is similar to the -5 volt regulator described in detail above. Transistor A12Q1 is a
switching transistor. The inverter controller is A12U1; A12R4 is the over-current sensing resistor and A12R10, A12R11,
and A12R9 are the voltage-sensing resistors.
FAN CIRCUIT AND FAN <16>
The fan used in the instrument has a brushless motor. Fan speed is controlled by the emitter voltage of A12Q65, which is
determined by the voltage dividing ratio of A12R66, A12R68, A12R67, and A12RT65. When the temperature rises, the
voltage drop across thermistor A12RT65 decreases, and this increases the base-emitter voltage of Al 2065. As a result,
the fan is accelerated.
DETAILED CIRCUIT DESCRIPTIONS FOR THE 338
The following paragraphs contain theory of operation information for the 338 Logic Analyzer. For information on the theory
of operation for the 318 Logic Analyzer, refer to the Table of Contents and preceding sections of this chapter.
338 A01 INPUT A BOARD <19> <20>
A02 INPUT B BOARD <21> <22>
The Input section consists of the Input A (A01) and the Input B (A02) boards. The block diagram for these boards is
shown in Figure 4-15. Since both of these boards share the same function, they are discussed as a unit in this description.
OVERVIEW
Refer to schematics <19>, <20>, <21>, and <-22,>. Data from Pod A (channels 0-7) flows to the internal buffers of the
M218s on the A02 Input B board < 21 >, and their outputs are supplied to the first latches and glitch recognizers (also in
the M218s) through delay lines. Only data supplied by Pod A is processed through the glitch detection circuitry. Data from
Pods B, C, and D is routed to the data buffers on the A02 Input B board <22>, and their output goes to the first latch
through delay lines. The word recognizers work with the latched data from all four pods, and their outputs are wire-ORed
on the A02 and A08 boards.
Qualifier data from each probe goes through qualifier buffer A02U250 <22> and then reaches the A03 acquisition control
board. The address decoder on the A01 board A01U112 and A01U114 <19> generates signals to set up the word
recognizers, select the clock, and enable the glitch trigger circuitry. When selected, an external clock signal enters the
FET buffer, A02Q108 <22>, and is compared with the external clock threshold; the resulting signal is distributed through
the clock selector to the first latches. When the internal clock is selected by the clock selector, the signal is processed in
the same manner as the external clock.
The threshold-level shifter converts threshold-level signals from the A05 ROM/Threshold board to fit the P6451 threshold
requirements.
ADDRESS DECODER <20>
The address decoder circuit consists of A01U112 and A01U114. A01U112 decodes 1/0 addresses 00, 01, 02, and 03.
A01U114 is a TTL-to-ECL-level converter. I/O address 00 (A01U114 pin 2) is for writing trigger word data into the word
recognezer (WR) for channels 0 through 15. I/O address 01(A01U114 pin 1) is used to write trigger word data into the
4-40
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 ...