Service manual

21
Test Points
Table 3-3 lists test points that are referred to in many of the troubleshooting procedures. Each test point is identified by a
circled number (e.g.,
), the circuit point (e.g., U308-1), and signal name (e.g., CV PROG). The "Measurement and
Conditions'' column describes the signal that should be measured and the conditions (e.g. operating mode) required to make
the measurement. The circuit locations of the test points are shown on the troubleshooting diagrams (Figures 3-3 through
3-11), and on the component locations diagrams that accompany the schematic sheets.
Note: When taking measurements, make sure that you connect the DMM or oscilloscope common to the proper
circuit common as indicated in Table 3-3.
Table 3-3. Test Points
Test Point
Number
Signal Measurement and Conditions
GPIB BOARD
Connect meter or scope common to test point
when taking measurements at test points
through
- C233
Primary/Chassis ground -
+ C233
+ 5V (primary bias) + 5V (4.8 to 5.2V)
cath -D212
+ 13V (primary bias rectifiers) + 13V (13 to 17 Vdc)
J2-10
PCLR1
Held low (0V) for 80ms (approx.) at power on and then goes
high (5V).
Q201-3
PCLR Goes high for 80ms (approx.) at power on and then goes low.
Q201-12
PCLR
Held low for 80ms (approx.) at power on and then goes high.
Q201-6
EEPON
At power on, holds the EEPROM's clock off to protect against
accidental data write when power is initially applied.
CONTROL BOARD
Connect meter common to test point
when taking measurements at test points through .
+C352
Secondary common
W1
+5V secondary bias +5V (4.8 to 5.2V)
+C353
+ 15V secondary bias
+ 15V
± 1V
- C352
-15V secondary bias
- 15V
± 1V
cath -D315
+ 26V (secondary bias rectifiers) + 23V to + 29V
Q301-12
SPCLR
Held low for 80ms (approx.) at power on and then goes high.
Q301-6
EEPON
At power on, holds the EEPROM's clock off to protect against
accidental data writes when power is initially applied.
U333-7
SRX Secondary receive serial data line. Toggles between 0 and 5V.
U334-3
STX Secondary transmit serial data line. Toggles between 0 and 5V.