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MAINTENANCE
Table 7-6. Static Sensitive Devices
Circuit
Designation
Description
Q301
N-channel
JFET, 2N5434
Q304-Q306
N-channel
JFET, 2N4392 (Selected)
UlOl
Microprocessor,
68008LlO
u102
RAM, 8832
u103
ROM
u104
ROM
u105
ROM
U127
GPIA, 9914
U301, U302
NVRAM,
2443
u315
PIA, 6821
U316
DMA controller,
4500
U317-U320
Dynamic
RAM, 666SA
U323
VIA, 6522
u337w340
Dynamic
RAM, 6665A
U361
CMOS Shift Register, 4094
U362, U363
12.bit DAC, DAC-80
U364-U367
CMOS Decoder/Driver,
HI'-26311
U388
A/D Converter
Module
U404, U407
I'IA, 65C21
u410
VIA, 6522A
U416, U419
12-bit DAC, DAC-80
Keithley
Part No.
TG-174
TG-77
LSI-69
LSI-76
194.Sol-**
194-802-'*
194.803"*
LSI-49
IC-353
LSI-8
LSI-64
LSl-63
LSI-28
LSI-63
IC-251
IC-323
IC-327
MO-4
LSl-61
LSI-45
IC-323
**Last two digits depend on current software revision
level.
7.7 DISASSEMBLY
Removing the Top Cover
The following
paragraphs contain disassembly procedures
1. Remove
the two screws that sccuw
the
top co\.er to the
for the Models
194 and 1944. Generally,
disassembly
rear panel.
should be carried out in the order presented here unless
2. Carefully
slide the top cover to the mar of the instru-
otherwise
noted.
ment until it is free of the case sides then wmpletcl)
remove it.
WARNING
Disconnect
the line cord
and all other
equip-
ment from the instrument
before
beginning
the
disassembly
procedure.
Removing the Bottom Cover
1. Place the Model 194 upside dwvn on a soft cklth to .woid
scratchine the case.
7.7.1 Top and Bottom
Cover Removal
2. Remove the two screws that secure the cover tu the war
panel.
3. Remove the four feet located on the bottom awcr.
Refer to Figure 7-7 and remove the top or bottom cover us-
4. Slide the bottom cover to the rear of the instrument
un-
ing the corresponding
procedure below.
til it is free of
the
case and remove it complrtely.
7-13
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