Mtb Trigger Pre-Amplifier - Philips PM3055 Service Manual

5-2
This stage comprises the following functions:
^
R7006 on D2201-1
for ch. A
and POS
B R7008
D2201-8
for ch,
B.
-
Channel
B normal/invert
(high
is INVERT) on D2201-7.
(The
balance between normal/invert can
be
adjusted with R2212)
-
Trigger view
invert (high
is INVERT) on D2202-2.
-
Trace separation control with R7013 on D2202-8.
*
on
|ta£e3(D22^
serves
as delay line driver where
the output
current
Hnf."
converted into voltage signal applied
to the delay
R2231
^d
R224r"
The current
regulation
for the
common-mode circuit
transistor D2203
(12, 13, 14).
is
achieved by
5.2 MTB TRIGGER PRE-AMPLIFIER
Trigger possibilities
are:
name
ch. A
TRAM+,
ch.
B
TRBM+,
EXTERNAL
EXT-,
line
LINE
Signal
routed
to
TRAM-
D2302(3,4)
TRBM-
D2302(5,6)
EXT+
D2303(3,4)
D2303(5)
Selected
by:
name
routed
to
AM
D2302(10)
BM
D2302(ll)
EXTM
D2303(10)
LNM
D2303(ll)
inverted
by:
name
routed
to
INVAM D2302(2)
INVBM D2302(7)
INVAM 02303(2)
INVAM 02303(7)
02301 serves
as
a
signal splitter and receives
the attenuator
unit. This input current signal
identical differential output current
signals
-
EXT MTB signal (pin
6
and
11)
its input
signal from
is copied into two
for
:
-
EXT 0TB signal (pin
7
and
10),
(see
Section
5.3).
The
symmetrical output currents from 02302
(13, 14) and
02303
(13 14)
commol\aL'
V232r
nI^!
r
followed by
a shunt feedback circuit V2318 and
if
110 mV/DIV
sensitivity
at
the
collectors of V2318
and V2321
At this point the signal path
is divided
into:
-
a trigger
path, fed
to
both V2333
and V2334, where depending on
the
current
to the
base, levelling of the trigger signal
is
obtain^
Two
separate series feedback circuits take
care of
voltage-to-cu^rent
conversion:
*
'-urrenc
V2341
and V2342
for main time—base triggering,
trigger output signal, TRIGM- and TRIGM+
are fed
to
the time-
base unit
A4,
•--•-iuc
*
V2347
and
V2349
for trigger view,
(^fg^^iefBA^)!
balanced by potentiometer R2407
The TRIGV+ and TRIGV- signals are
fed
to
D2202
(3~4).