Wahl Heat-Prober 392AHP, Руководство пользователя

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Heat-Prober
®
Platinum-RTD Thermometers User Manual
28
392 SERIES TROUBLE SHOOTING PROCEDURE
Step Problem Action to be Performed If Correct If Incorrect
1.
Blank
Display*
Measure voltage at U6-19 with DVM.
It should be at +4.3 ±.2V.
Proceed to Step 3.
Proceed
to Step 2.
2.
*
Repeat above measurement, but with
(+) lead at Q4 emitter.
Check for open
trace between Q4
emitter and U6-19.
Go to Step 4.
3.
Check U4-25 with an oscilloscope. It
should be a 3.58MHz square wave with
levels from 0 to 5 volts.
Replace U6. If still no
display, go to Step 9.
Replace U4.
If still no dis-
play, go to
Step 7.
4.
*
Check voltage at Q4 collector. It
should be equal to the battery voltage
or applied voltage from test power
supply.
Proceed to next
step.
Check for
open
trace from
Pin
5 to Q4 (C).
5.
Check voltage on junction of R30 and
CR5 cathode. Should be
+5.000 ± .005V.
Proceed to next
step.
Go to Step 8.
6.
*
Check voltage on junction of R30 and
Q4 base. It should be between
+4.7 and +4.9 volts.
Replace Q4.
Replace
R30.
7.
Replace Yl crystal and repeat Step 3. Done.
Go to Step
16.
8.
No +5000
volts or
incorrect
Measure voltage at U2-2. It should be
+2.5 volts ± 0.1V.
Go to Step 11.
Proceed
to next
step.
9.
Measure voltage at pin 5 of wire
harness. It should be equal to the
battery or power supply voltage.
Proceed to next
step.
Check wire
harness for
broken
wires.
10.
Check voltage at U7-2. It should be
+2.5 volts ± 0.1V.
Proceed to next
step.
Replace U7.
11.
Check voltage at Q2 between base and
emitter, there should be approx. a 0.7V
drop.
Replace Q2. If still
incorrect go to Step
16.
Replace
U2 and
check
CR3, CR4,
R19, R20
& R22.
12.
Unit
constantly
reads - OL-
Measure voltage at U4-28 with DVM.
It should be -4.3 ± 0.1V.
Proceed to next
step.
Proceed
to Step
14.