Philips PM32671 Service Manual page 29

2.2.6. Delay-line driver
The delay-line driver consists of the Hooper stage V633lV634 and Cherry stage V636lV637. The Hooper stage
has an additional compensation circuit with operational amplifier D636. One input of D636 measures the
divider R692lR693. In the event of voltage differences between both inputs, the output of D636 compensates
for this via R662lR663 to the bases of V663 and V664. As a result, under no signal conditions, the collector
voltages of V633 and V634 are constantly held a t 9 V. This is necessary in order to obtain equivalent dynamic
ranges for both halves of the amplifier stage.
The Cherry stage
matches the impedance of the delay line.
A signal used for composite triggering is picked off from the collectors of V 633 and V634 by Cherry stage
Final vertical amplifier
The signal from the delay line (Unit 8) is terminated by the delay line compensation circuit consisting of
Cherrry stage V1204lV1206 together with the common-current source V1203. The emitter circuit of V12041
temperature. The Cherry stage V1204lV1206 is followed by a Hooper stage V1209/V1211. This stage also
receives the trace separation control signal that gives a vertical shift between the main and delayed time-base
displays in the alternate time-base mode.
The Hooper stage is followed by another Cherry stage V1213/V1214 with common-current source V1212.
This stage incorporates a gain adjustment preset R1256 and
stage drives output amplifier
results in an increase a t the high frequency end of the bandwidth of the oscilloscope.
IC, D1201. The collector load resistors of the output amplifier are part of
square-wave adjustment C1224. The Cherry
a
2-13
stage