HP 6236A Operating And Service Manual page 22

Table 5-3. Initial Troubleshooting Procedure (Continued)
STEP ACTION RESPONSE NEXT ACTION
3
Check output of +6V supply a. Normal a. If the output of this supply is normal
(Model 6236A)
unloaded but its voltage falls when
or +18V supply
loaded, check the current limit adjust-
(Model 6237 A).
ment, Paragraph 5-16, steps (p) thru (s).
b. High, low, or zero
b. Proceed to Table 5-7.
output voltage.
Table 5-4. Bias and Reference Voltage Check
STEP
ACTION RESPONSE
PROBABLE CAUSE
1 Check +7.5V bias, TP1 to a. Normal
a. Proceed to step (2).
common
(+7.5V ±5%)
b. Voltage high
b. Check VR3 for open.
c. Voltage low
c. Check VR3 for short.
Note: A short within U1, U2, U3, or U4
can cause low +7.5V or -12.4V bias voltages.
2
Check -6.2V reference,
a. Normal
a. Proceed to step (3).
TP2 to common
(-6.2V ±5%)
b. Voltage high
b. Check V R1 for open.
c. Voltage low
c. Check VR1 and Q14 for short, VR2
and Q15 for open. (A short within U4
could reduce this voltage.)
3
Check -12.4 V bias,
a. Normal
a. Proceed to +20V supply troubleshooting.
TP3 to common
(-12.4V ±5%) Table 5-5.
b. High voltage b. Check Q11 for short, Q12 for open,
and Z1 for open between pins 3 and 5.
c. Low voltage
c. Check Q11 for open, Q12 for short,
and Z1 for open between pins 1 and 3.
5-8