Circuit Description—221 Service
BRIDGE
RECTIFIER
CR612
CR613
CR614
CR615
POWER INVERTER
RFI
FILTER
P610
LINE
INPUT
LINE
INVERTER
0622
Q626
T623
RECTIFIERS
T633
CR633
CR632
REGULATOR
+5
-5
SECONDARY
INVERTER
Gl
REFEF
Af
U6
4D
=IENCE
rfP
54
I
ON
I
S738
+48 V
+76 V
Fig. 4-4. Simplified block diagram of the Power Supply circuit.
The c irc u it from the pow er line to the prim ary o f
T633 is floating at line potential. Any signal
measurem ent in this c irc u it m ust be referenced to
pin 1 of T633, and should be measured only if an
Isolation transform er is used on the pow er line.
Power Supply
The 221 Power Supply circuit is divided into three
sections; the Power Inverter, the +5 V - 5 V Regulator, and
the HV Inverter. A block diagram of the Power Supply is
shown on Fig. 4-4. The schematic of the Power Supply is
shown on diagram 4.
When the instrument is connected to a power source,
C612, R612, C613, R613, R614, L610, and C614 function as
a RFI filter to minimize RFI interference. The line voltage is
rectified by diode bridge CR612, CR613, and CR615,
which supplies the dc voltage for the Line Inverter circuit.
Transistors Q622 and Q626 convert the dc voltage into a
square-wave voltage. The square-wave voltage is applied
to an LC resonant circuit consisting of C623 and T633.
Feedback is provided from T633, through R626, back to
the base drive transformer T623, to sustain the oscillation.
As the output power changes, the frequency of the square-
wave changes with respect to the resonance of L (T633)
and C (C623), permitting the Power Inverter to remain
constant. In this way a correct output level is maintanined
over the specified line voltage range and operating
conditions.
4-6
REV. B, AUG 1974
Содержание 221
Страница 4: ...Fig 1 1 The Tektronix 221 Oscilloscope 221 Service http manoman sqhill com ...
Страница 54: ...REV B j JU L Y 19 7 4 BLOCK DIAGRAM ...
Страница 70: ...1573 34 REV C FE S 5 7 9 C R T C I e c u IT S W E 2 Z i O S C IL L O S C O P E ...
Страница 76: ......
Страница 77: ...221 OSCILLOSCOPE ...