Fluke 123B/S Service Manual - Page 127

Reference Voltages, 5.10 Buzzer Circuit, If not correct check/replace V301, R307, C3112

Page 127 highlights

7 Corrective Maintenance 7.5 Miscellaneous Functions Press to open the SCOPE OPTIONS ... menu, and select: SCOPE MODE: I NORMAL | WAVEFORM MODE: I NORMAL 7. Supply a 15.6 kHz square wave of 20V (+10...-10V) to Input A, and Input B. 8. Check: a. TP308 (TVOUT) for 15.6 kHz, -0.8...+0.6V pulse (square wave) bursts (see figure below). 15.6 kHz ≈600 ms If not correct, N301 may be defective. b. TVSYNC, on R392/R397, for 15.6 kHz, +2.6...+3.3V pulse bursts. If not correct, V395 may be defective. c. TP311 (ALLTRIG) for 15.6 kHz, +3.3...0V pulse bursts. If not correct, N301 may be defective. d. TP433 (TRIGDT) for 0...+3.3 pulses. If not correct, TRIGQUAL may be not correct. e. TP338 (TRIGQUAL) for 0...+0.6V pulses, width 70 µs, frequency about 2 kHz. If not correct, D471 may be defective. 7.5.9 Reference Voltages 1. Check: a. TP306 for +3.3V, TP307 for +1.23V If not correct check/replace V301, R307, C3112, P-ASIC N501. b. TP301 for +2V TP303 for -1.23V TP302 for +0.4V TP304 for +3.3V TP310, see figure below (in ROLL mode TP310 is zero). If not correct, check/replace REFERENCE GAIN circuit and T-ASIC N301. +1.2V TP310 ≈ 800 ms -1.2V 7.5.10 Buzzer Circuit 1. Press and select MEASURE on A : CONT ))) 2. Short circuit Input A to COM. The buzzer is activated now. 3. Check TP496 for a 4 kHz, 0...3V square wave during beeping (0 V if not activated). 4. Check TP495 for a 4 kHz +3...-30V square wave during beeping (TP495 is -30V if the beeper is not activated). 7-15

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Corrective Maintenance
7.5 Miscellaneous Functions
7
7-15
Press
to open the
SCOPE OPTIONS ...
menu, and select:
SCOPE MODE:
NORMAL | WAVEFORM MODE:
NORMAL
7.
Supply a 15.6 kHz square wave of 20V (+10...-10V) to Input A, and Input B.
8.
Check:
a.
TP308 (TVOUT) for 15.6 kHz, -0.8...+0.6V pulse (square wave) bursts (see
figure below).
15.6 kHz
600 ms
If not correct, N301 may be defective.
b.
TVSYNC, on R392/R397, for 15.6 kHz, +2.6...+3.3V pulse bursts.
If not correct, V395 may be defective.
c.
TP311 (ALLTRIG) for 15.6 kHz, +3.3...0V pulse bursts.
If not correct, N301 may be defective.
d.
TP433 (TRIGDT) for 0...+3.3 pulses.
If not correct, TRIGQUAL may be not correct.
e.
TP338 (TRIGQUAL) for 0...+0.6V pulses, width 70
µ
s, frequency about 2 kHz.
If not correct, D471 may be defective.
7.5.9 Reference Voltages
1.
Check:
a.
TP306 for +3.3V, TP307 for +1.23V
If not correct check/replace V301, R307, C3112, P-ASIC N501.
b.
TP301 for +2V
TP303 for -1.23V
TP302 for +0.4V
TP304 for +3.3V
TP310, see figure below (in ROLL mode TP310 is zero).
If not correct, check/replace REFERENCE GAIN circuit and T-ASIC N301.
+1.2V
-1.2V
800 ms
TP310
7.5.10 Buzzer Circuit
1.
Press
and select
MEASURE on A : CONT
)
)
)
2.
Short circuit Input A to COM.
The buzzer is activated now.
3.
Check TP496 for a 4 kHz, 0...3V square wave during beeping (0 V if not activated).
4.
Check TP495 for a 4 kHz +3...-30V square wave during beeping (TP495 is -30V if
the beeper is not activated).