SERVICING
7-4
Revised January 1995
Part No. 001-9750-003
divide number is correct, continue the checks which
follow.
Phase Detector - When the VCO is not locked on
frequency, the fR and fV inputs to the phase detector
are probably not the same frequency. Measure the
frequency at fR (pin 13) and fV (pin 3) and then check
the phase detector outputs (DOWN and UP pins). If
the phase detector is operating properly, these outputs
should be as follows:
fV greater than fR - The negative-going pulses on
the DOWN output (pin 15) should be much wider
than the negative-going pulses on the UP output
(pin 16). The DC voltage on pin 12 of the VCO
module should be near 1 volt.
fV less than fR - The negative-going pulses on the
UP output (pin 16) should be much wider than the
negative-going pulses on the DOWN output (pin
15). The DC voltage on pin 12 of the VCO should
be near 20 volts.
If the preceding phase detector output signals are
not measured when the VCO is out of lock, U801 or
the charge pump circuit may be defective. If the phase
detector and charge pump are operating properly,
check the lock detector and prescaler as described in
the following information.
When the VCO is locked on frequency, the
following waveforms should be observed at the points
indicated (all pulses should occur simultaneously).
Lock Detector -
When the VCO is locked on
frequency, the waveform at U801, pin 7 should be as
follows. The lock detect signal on the collector of
Q809 should then be low. When the VCO is unlocked,
the negative-going pulses should be much wider than
those shown and the signal on the collector of Q809
should be high (5V).
Modulus Control Signal -
The frequency of the
modulus control output on U801, pin 12 should be
equal to the N counter output frequency on pin 3
(either in or out of lock). When the VCO is in lock,
this frequency should be the fR frequency (12.5 kHz).
The duty cycle of the modulus control signal
determines the divide number of the prescaler. The
duty cycle should be as follows:
If the modulus control signal is not correct, U801
may be defective or the logic may not be programming
the correct divide number.
T1
T2
=
A counter divide number
N counter divide number
Содержание Summit DM 975x
Страница 105: ...MULTI NET SYSTEM OVERVIEW 5 10 Revised February 1997 Part No 001 9750 005 ...
Страница 108: ...CIRCUIT DESCRIPTION 6 3 August 1993 Part No 001 9750 001 Figure 6 1 Transceiver Block Diagram ...
Страница 123: ...CIRCUIT DESCRIPTION 6 18 August 1993 Part No 001 9750 001 ...
Страница 131: ...SERVICING 7 8 Revised January 1995 Part No 001 9750 003 ...
Страница 156: ...9 19 Revised December 2000 Part No 001 9750 007 TRANSCEIVER EXPLODED VIEW PART 1 ...
Страница 157: ...Revised January 1995 Part No 001 9750 003 9 20 TRANSCEIVER EXPLODED VIEW PART 2 Remote Control Parts ...
Страница 168: ...Revised January 1995 Part No 001 9750 003 10 11 INTERCONNECT SCHEMATIC ...
Страница 169: ...Revised January 1995 Part No 001 9750 003 10 12 DISPLAY BOARD SCHEMATIC ...
Страница 170: ...Revised January 1995 Part No 001 9750 003 10 13 DISPLAY BOARD TOP VIEW DISPLAY BOARD BOTTOM VIEW ...
Страница 171: ...Revised January 1995 Part No 001 9750 003 10 14 RF BOARD SCHEMATIC REVISED 800 MHZ ...
Страница 172: ...Revised January 1995 Part No 001 9750 003 10 15 RF BOARD BOARD LAYOUT ALL 800 900 MHZ ...
Страница 173: ...Revised January 1995 Part No 001 9750 003 10 16 RF BOARD BOARD SCHEMATIC 900 MHZ ...
Страница 174: ...Revised January 1995 Part No 001 9750 003 10 17 RF BOARD BOARD SCHEMATIC UNREVISED 800 MHZ ...
Страница 178: ...Revised January 1995 Part No 001 9750 003 10 21 PA BOARD SCHEMATIC 900 MHZ 30W ...
Страница 179: ...Revised January 1995 Part No 001 9750 003 10 22 PA BOARD SCHEMATIC 900 MHZ 15W ...
Страница 180: ...Revised January 1995 Part No 001 9750 003 10 23 PA BOARD BOARD LAYOUT 900 MHZ UNREVISED 800 MHZ 15W 30W 35W 15W MODELS ...
Страница 181: ...Revised January 1995 Part No 001 9750 003 10 24 PA BOARD SCHEMATIC UNREVISED 800 MHZ 35W ...
Страница 182: ...Revised January 1995 Part No 001 9750 003 10 25 PA BOARD SCHEMATIC UNREVISED 800 MHZ 15W ...
Страница 183: ...Revised January 1995 Part No 001 9750 003 10 26 AUDIO LOGIC BOARD SCHEMATIC PART 1 OF 2 ...
Страница 184: ...Revised January 1995 Part No 001 9750 003 10 27 AUDIO LOGIC BOARD SCHEMATIC PART 2 OF 2 ...
Страница 185: ...Revised January 1995 Part No 001 9750 003 10 28 AUDIO LOGIC BOARD LAYOUT TOP VIEW ...
Страница 186: ...Revised January 1995 Part No 001 9750 003 10 29 AUDIO LOGIC BOARD LAYOUT BOTTOM VIEW ...
Страница 188: ...Revised January 1995 Part No 001 9750 003 10 31 REMOTE TRANSCEIVER INTERCONNECT SCHEMATIC ...
Страница 189: ...Revised January 1995 Part No 001 9750 003 10 32 REMOTE CONTROL UNIT INTERFACE BOARD SCHEMATIC ...
Страница 216: ...Part Number 001 9750 007 12 00 hph Printed in U S A ...