Philips PM32671 Service Manual page 85

5-1 4
5.5.3.3. Final Y amplifier balance
- Interconnect both inputs of the delay line.
- Adjust R1213 (fig. 5.2.) on the final Y amplifier unit so that the trace is just in the vertical mid of the
screen. Disconnect both inputs of the delay-line.
0 of S17 and S18.
- Depress
-
Put the AMPL/DIV switches in position 20mV/div.
- Turn the channel A position control R1 fully counter clockwise.
-
Turn the channel B position control R2 fully clockwise.
- Depress ADD of S1.
-
Position the trace in the vertical mid of the screen by means of R660 (fig. 5.2.).
- Depress ALT of S1.
- Position the channel
- Depress ADD of S1 and read out the vertical distance between the trace and the vertical mid of the screen.
- Depress B of S1 and adjust R660 (fig. 5.2.) so that a vertical distance is obtained equal to the one measured
in the previous step.
- Check the adjustment as follows: depress ALT of S1 and position the channel A and B traces in the vertical
mid of the screen.
- Depress ADD and check if the trace is s t i l l in the vertical mid of the screen.
LF
5.5.4. corrections and sensitivities
The LF corrections and sensitivity adjustments of channel A and B are identical.
The knobs, sockets and adjustments for channel B are shown in brackets behind those of channel A.
5.5.4.1. Continuous control of channel A (B)
- Depress A (B) of S1.
- Depress A (B) of S23.
- Set the AMPL/DIV switch
- Apply a square-wave signal, freq. IOkHz, ampl. 100mV approx. to input A (B), giving 5 div. deflection on
screen.
- Turn the continuous control CAL R7 (R8) 15' counter clockwise out of i t s CAL position.
- Check that the continuous attenuation starts a t this position of the continuous control; if necessary readjust
R622 (R8221, fig. 5.2.
-
Turn the continuous control CAL R7 (R8) fully counter clockwise.
- Check that the trace height i s
5.5.4.2. LF correction of channel A (B)
- Set the controls as indicated in fig. 4.1.
-
Set the MTB TIME/DIV switch S15 to 20ms.
-
Set the AMPL/DIV switch S9 (S11) to 20mV.
- Apply a square-wave signal, frequency IOOHz, ampl. 100mV to input A (B).
- Check that the pulse top is as straight as possible; if necessary readjust R538 (R738). fig. 5.2.
NOTE: Check if the AMPL/DIV balance, the normal/invert balance and the final Y amplifier balance are still
within tolerance. If not repeat paragraphs 5.5.3.
XI
5.5.4.3. Gain
(sensitivity) channel A (B)
- Set the MTB TIME/DIV switch to 0.2ms.
- Apply a square-wave signal, freq. IOkHz, ampl. 100mV to input A (B).
- Set the AMPL/DIV switch
-
Depress A (B) of S1.
- Depress A (B) of S23.
-
Check that the trace height is 5 div.
A and B traces in the vertical mid of the screen by means of R1 and R2.
2 div., if necessary readjust R617 (R8171, fig. 5.2.
+
or - 3%
and 5.5.3.3.
if necessary readjust R1256 (R779), fig. 5.1. (fig. 5.2.).
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