Philips PM32671 Service Manual page 87

5-16
5.5.5.2. Input capacitance, channel A (B)
-
Apply via dummy probe (fig. 5.5.) a square-wave signal, freq. IOkHz, rise-time
a
- Check the square-wave response; check that the pulse top errors do not exceed
Channel A
2 mV
5 mV
20 mV
50 mV
v
0.1
v
0.2
0.5 V
2 v
5 v
v
Fig. 5.5. Dummy probe
- Remove input signal and dummy probe.
All HF square-wave adjustments must be carried out with
This compensates for H F square-wave response changes a t high ambient temperatures
5.5.5.3. HF square-wave response channel A
- Set the controls as indicated in fig. 4.1.
- Set the AMPL/DIV switch S9 to 20mV.
- Apply to X2 (A) a square-wave signal a t 120mV, frequency 1MHzand with a rise-time
-
Set the TIME/DIV switch S15 to 0 . 2 ~ .
- Using C1211 and C1244 (fig. 5.2.) adjust the square-wave response as straight as possible (see fig. 5.6.).
Fig. 5.6. Adjustment of HF square-wave response
Amplitude of input
signal A
24 mV
60 mV
240 mV
600 mV
v
1.2
2.4 V
6 V
v
12
24 V
30 V
30 V
2 : 1
on the final Y amplifier (unit 9).
820921
+
or - 1 % ; if necessary
Adjusting element
channel A
Adjust Cd (dummy)
C512
C504
25pF
a resistor of 215 k a switched in parallel with
Trace height
+ o r -1%
6 div.
6 div.
6 div.
6 div.
6 div.
6 div.
6 div.
6 div.
6 div.
6 div.
3 div.
1.5 div.
Ins.