Pwm Circuit; Randomize Circuit; Loading Software - Fluke ScopeMeter 123 Service Manual

7.5.14 PWM Circuit

1. Check the PWM control signals generated by D471. The signals must show 0...3V
pulses, with variable duty cycle, and a frequency of 100, 25, or 6 kHz:
a. CHARCURD, CONTR-D
b. SADCLEV, POS A-D, BACKBRIG, POS B-D,
TRIGLEV2D, TRIGLEV1D, HO-RNDM
c. OFFSETA-D, OFFSETB-D
2. If not correct, check:
a. TP306 (REFPWM2) for +3.3V (used for CHARCURD SADCLEV)
b. TP304 (REFPWM1) for +3.3V (used for other PWM signals).
If TP306 and TP304 are correct, D471 may be defective.

7.5.15 Randomize Circuit

1. Check TP483 for 0...+3V pulses, 25 kHz, variable duty cycle
2. Check TP482, for +3...0V pulses, variable frequency and duty cycle.

7.6 Loading Software

To load instrument software in the test tool, the Fluke-43-123-19x ScopeMeter Loader
program is required.
Power the test tool via the power adapter input using the BC190 Power Adapter.
Some units having serial numbers below DM7000000 can give the error message
Error 8: No connection possible with UHM
because they require a 20V ± 1VDC (0.5 A) voltage on the Power Adapter input (units
having an Intel FlashROM). For this purpose, a special supply cable, also advised for
calibration, can be ordered (See figure 7-2). See Section 8.7. for the ordering number.
To avoid damaging the test tool be sure to apply the polarity and
voltage level of the 20V supply voltage correctly.
-
+
CAUTION
Figure 7-2. 20V Supply Cable for Loading Software
Corrective Maintenance

7.6 Loading Software

≅ 100 kHz
≅ 25 kHz
≅ 6 kHz
+
RED
-
WHITE
7
7-17