Levels Of Channels A And B; Sensitivity Of Channels A And B; Ac-Dc Switch; Check Zero; Square-Wave Response - Philips Pm 3342 Manual

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2. Channel B
R313 (Fig. 6)
- Set "MODE" (SKS) to "B" and turn "D.C. BAL."
(R8) to its mid-position.
During this adjustment, keep the time-base line on
the screen with "SHIFT" (R7).
- Adjust the coarse control "D.C. BAL." (R313) so,
that the time-base line hardly moves when "V/cm"
(RS) is turned fully clockwise or anti- clockwise.
- With the fine control "D.C. BAL." (R8), adjust for a
stationary display.
3. Trigger amplifier
R605, R623 (Fig. 6)
The d.c. balance and the output level of the trigger am-
plifier are adjustable with "BAL." (R605) and choice
resistor R623.
These adjusting elements are accessible if the unit to
be measured is connected to the basic oscilloscope via
the extension plug.
Short-circuit the input of the trigger amplifier by
interconnecting the bases of transistors TS602 and
TS 603 (See Fig. 6).
Measure the voltage on the output of the amplifier
between the emitters of transistors TS608 and TS609.
(See Fig. 6).
Adjust this voltage to minimum with "BAL" (605R).
Check the voltage level of both points with respect
to earth; this should amount to -~ 18 V, tolerance
-~ or — 2 V.
If necessary select a different value for R623.
Remove the interconnection.
C. LEVELS OF CHANNELS A AND B
- Set "MODE" (SKS) to "A" and adjust "SHIFT"
(R1) so that the trace does not jump when "POLA-
RITY" (SK2) is switched-over.
- Set "MODE" (SKS) to "B" and adjust "SHIFT" (R7)
so that the trace does not jump when "POLARITY"
(SK8) is switched-over.
- In both cases, the vertical position of the time-base
line should not diviate more than 1 cm from the
centre of the screen.
D. SENSITIVITY OF CHANNEL A AND
CHANNEL B
- Set the below mentioned knobs to the following
positions:
"V/cm" (SK4) and "V/cm" (SK10) to ".O1"
"MODE" (SKS) and "TRIGG." (SK6) to "A"
"V/cm" (R3) and "V/cm" (RS) to "CAL".
Adjust the calibration voltage of the basic oscil-
loscope to 40 mV and apply this voltage to channel A.
- With "GAIN" (R4), adjust the sensitivity so, that
the trace height of the reproduced square-wave
voltage is 40 mm.
Set "MODE" (SKS) to "ADDED" and "POLARI-
TY" (SK2 and SK8) to "NORMAL" and "INVERT"
respectively.
Also apply the 40-m V calibration voltage to channel
B by interconnecting the inputs of both channels.
With "GAIN" (R6), adjust the sensitivity of channel
B so, that it is equal to that of channel A; in this
case no vertical deflection is visible.
- Set "MODE" (SKS) to position "A".
- Check that the sensitivity of channel A can be con-
tinuously controlled with "V/cm" (R3).
- With R3 fully anti-clockwise, the sensitivity should
be so reduced that the trace heigth does not exceed
16 mm.
- Set "MODE" (SKS) to position "B".
- Set "TRIGG." (SK6) to position "B".
Check that the sensitivity of channel B can be con-
tinuously controlled with "V/cm" (RS).
With RS fully anti-clockwise, the sensitivity should
be so reduced that the trace height does noet exceed
16 mm.
E. A.C./D.C. SWITCH; CHECK ZERO
- Set the below mentioned knobs to the following
positions:
"POLARITY" (SK2-SK8) to "NORMAL"
"A.C./D.C." (SK3-SK9) to "D.C."
"MODE" (SKS) to "A" and "B" respectively
"TRIGG." (SK6) to "A" and "B" respectively
"V/cm" (SK4 and SK10) to ".O1 V"
Adjust the calibration voltage of the basic oscillo-
scope to 40 mV and apply this voltage to channel A
(channel B).
Adjust "SHIFT" (R1) (R7) so, that the lower side
of the trace coincides with the centre line of the
screen.
Set SK3 (SK9) to "A.C."
In both channels the DC-components should be
blocked, as a result of which the trace is written
approximately symmetrically around the centre line
of the screen.
If "CHECK ZERO" is depressed, the trace should
no longer be visible.
F. SQUARE-WAVE RESPONSE
To avoid extra capacitive load on the output of the
amplifier, this adjustment should be carried out without
using the extension plug. To check the rise time and the
overschoot, a square-wave voltage with a value of 40
mVp_p and a rise time of 1.5 nsec. is required.
This voltage can be obtained with the aid of a pulser