Keithley 2015 Service Manual

4-8 Troubleshooting
Display board
Display board components are shown in the digital circuitry block diagram in Figure 4-2.
Figure 4-2
Digital circuitry block diagram
Microcontroller
U401 is the display board microcontroller that controls the display and interprets key data.
The microcontroller uses three internal peripheral I/O ports for the various control and read
functions.
Display data is serially transmitted to the microcontroller from the digital section via the TXB
line to the microcontroller RDI terminal. In a similar manner, key data is serially sent back to
the digital section through the RXB line via TDO. The 4MHz clock for the microcontroller is
generated by crystal Y401.
Distortion
Digital Circuit
(See Figure 4-4)
Keypad
RS-232
U159
RS-232
Port
IEEE-488
Bus
GPIB
U158, U160,
U161
TDTX
TRIG IN
XADTX
TDCLK
TRIG OUT
XADCLK
TDTS
XADTS
XTDRX
XADRX
Scan Control
XTAL
Y101
Display
DS401
ROM
U156, U157
68306
U135
ROM
U156, U157
Display Board
Controller
U401
NVRAM
U136
Trigger
U146, U164
Trigger
Link
Analog
Circuitry
(See Figure 4-3)
O
P
T
O
I
S
O
AT101
U150
U155
µP
ADTX
ADCLK
ADTS
ADRXB
IN
OUT
IN
OUT

Keithley 2015 Specifications

General

Model	Keithley 2015
Category	Multimeter
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Frequency Range	3 Hz to 300 kHz
Resistance Range	100 MΩ
DC Current Range	3 A
DC Current Accuracy	0.05%
AC Current Range	3 A
Display	5.5 digit
Connectivity	GPIB
Power Supply	100 V to 240 V AC, 50 Hz to 60 Hz