Honeywell XK516D1 Maintenance Manual page 64

The RF signal is forwarded via coupling capacitor, C74, to matching network C71,
R127, and transformer, T5, or the input of the final stage. C225 is wired in parallel
to the output of transistor, T5, for compensation purposes. The RF signal is supplied
via coupling capacitors, C77 and C78, which are used for direct voltage isolation.
To optimize the frequency response, and for stabilization purposes at low frequen-
cies, the signal amplified by transistors, V38 and V41, is transformed via T4 and
looped back via the parallel connection of R123, R135, or R124, R143.
The drain/source voltage of 50V is supplied to transistors, V38 and V41, via the cen-
ter tap of transformer, T4. C63, C64, C66, C67, and C107 to C110 are used for fil-
tering purposes. Transformer, T3, combines the output signals of both amplifier
branches, and adjusts the amplifier at the output end. For compensation purposes,
the output is further wired with C97.
The gate bias is supplied to power FETs, V38 and V41, via potentiometers R141
and R145, via diodes V40 and V42, and resistors, R120 and R126. As far as direct
voltage is concerned, the transistors are referred to ground via R125 and R134;
C68 and C83 are used for filtering. The operating points of transistors, V38 and
V41, are set to permit ID = 2A to flow per transistor. The final stage has an amplifi-
cation of about 18dB, whereby an input impedance of about 5
terminal of C74.
The gate bias of final stage transistors, V38 and V41, is set in relation to the heat
sink temperature of the amplifier, or to the resistance of NTH thermistor, R155 by
voltage regulator, G2A. R156, R157, and RI58 are used to compensate the temper-
ature characteristic, while R175 and R176 have a current limiting function. The tem-
perature-compensated bias, and consequently the operating points of transistors,
V38 and V41, are switched ON and OFF by transistor, V46, depending upon the
OPOFF 5.3V logic signal (X2.45).
The +50V supply voltage of the final stage transistors is rectified by bridge-connect-
ed rectifier, V50, and filtered via choke, L14, and electrolytic capacitor, C1, before
being supplied via measuring resistor, R144 to the final stage. The falling voltage
across the measuring resistor is supplied to operational amplifier, N70-B, via the re-
sistance networks, R148, R152, R170, and R165, R149, R300, R301, R151. Here
it is amplified and passed on to X2.50 as the CSFS signal, as a measurement of the
final stage power consumption.
The +50V supply voltage is also divided by R171, RI72, and directed as the VSFS
signal to X2.49. C90 has a filtering function. In addition, the VSFS signal is conduct-
ed via R392, V300, and C300 for filtration purposes to comparator, N1-C, compared
with the VREF reference voltage (X2.52), divided by resistors, R303, R304, and fur-
ther processed as CM50V (X2.23). R305 functions as a pull-up resistor, R306 for
connecting the hysteresis of N1-C.
The reference voltage VREF (X2.52) is +4.9V
tor, G1-A, connected by R4, R24, R82, R23, and C16, C94.
The heat sink temperature of the amplifier board is measured with PTC thermistor,
R153, and converted to a voltage by N70-A. The connection of operational amplifi-
er, N70-A, serves the linearization of the PTC thermistor characteristic. Capacitors,
C58 and C59, are used to filter the supply voltages of N70. The TSFS signal (X2.47)
is about +1.55V with a cold heat sink (ambient temperature).
I.B.1516A
Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
23-12-01
Ω
is measured at the
±
0.1V, and is set by voltage regula-
Page 55 Page 35
Mar 30/01