VX-261 VHF FM Transceiver Service Manual
8
Introduction
The VX-261 is carefully aligned at the factory for the
specified performance across the frequency range speci-
fied for each version. Realignment should therefore not
be necessary except in the event of a component failure,
or altering version type. All component replacement and
service should be performed only by an authorized Vertex
Standard representative, or the warranty policy may be
void.
The following procedures cover the sometimes critical and
tedious adjustments that are not normally required once
the transceiver has left the factory. However, if damage
occurs and some parts subsequently are replaced, realign-
ment may be required. If a sudden problem occurs during
normal operation, it is likely due to component failure;
realignment should not be done until after the faulty com-
ponent has been replaced.
We recommend that servicing be performed only by au-
thorized Vertex Standard service technicians who are ex-
perienced with the circuitry and fully equipped for repair
and alignment. Therefore, if a fault is suspected, contact
the dealer from whom the transceiver was purchased for
instructions regarding repair. Authorized Vertex Standard
service technicians realign all circuits and make complete
performance checks to ensure compliance with factory
specifications after replacing any faulty components.
Those who do undertake any of the following alignments
are cautioned to proceed at their own risk. Problems
caused by unauthorized attempts at realignment are not
covered by the warranty policy. Also, Vertex Standard
reserves the right to change circuits and alignment pro-
cedures in the interest of improved performance, without
notifying owners.
Under no circumstances should any alignment be attempt-
ed unless the normal function and operation of the trans-
ceiver are clearly understood, the cause of the malfunction
has been clearly pinpointed and any faulty components
replaced, and realignment determined to be absolutely
necessary.
The following test equipment (and thorough familiarity
with its correct use) is necessary for complete realign-
ment. Correction of problems caused by misalignment
resulting from use of improper test equipment is not
covered under the warranty policy. While most steps do
not require all of the equipment listed, the interactions of
some adjustments may require that more complex adjust-
ments be performed afterwards. Do not attempt to perform
only a single step unless it is clearly isolated electrically
from all other steps. Have all test equipment ready before
beginning, and follow all of the steps in a section in the
order presented.
Required Test Equipment
RF Signal Generator with calibrated output level at
600 MHz
Oscilloscope
Deviation Meter (linear detector)
In-line Wattmeter with 5 % accuracy at 200 MHz
50 Ohm RF Dummy Load with power rating 10 W at
600 MHz
Regulated DC Power Supply (standard 7.5 V DC, 3 A)
Frequency Counter with 0.2 ppm accuracy at 200
MHz
Audio Signal Generator
AC Voltmeter
DC Voltmeter
VHF Sampling Coupler
IBM
®
PC/compatible Computer with Microsoft
®
Win-
dows
®
2000, XP, Vista or Windows7
Vertex Standard CE150 PC Programming Software
Vertex Standard FIF-12 USB Programming Interface
and CT-104A, CT-106, or CT-171 PC Programming
Cable.
Vertex Standard FRB-6 Tuning Interface Box and CT-
160 Connection Cable.
Vertex Standard CN-3 (P/N: A08760001) Antenna
Connector
Alignment Preparation & Precautions
A 50-Ohm RF Dummy Load and in-line wattmeter must
be connected to the main antenna jack in all procedures
that call for transmission, except where specified other-
wise. Correct alignment is not possible with an antenna.
Because of the BTL (Bridged Trans Less) Amplifier cir-
cuit used in the VX-261, do not connect earth side of the
speaker leads to chassis “ground”.
After completing one step, read the following step to de-
termine whether the same test equipment will be required.
If not, remove the test equipment (except dummy load and
wattmeter, if connected) before proceeding.
Correct alignment requires that the ambient temperature
be the same as that of the transceiver and test equipment,
and that this temperature be held constant between 68 and
86 °F (20 ~ 30 °C). When the transceiver is brought into
the shop from hot or cold air, it should be allowed time to
come to room temperature before alignment.
Whenever possible, alignments should be made with os-
cillator shields and circuit boards firmly affixed in place.
Also, the test equipment must be thoroughly warmed up
before beginning.
Note
: Signal levels in dB referred to in the alignment pro-
cedure are based on 0 dBµ EMF = 1 µV.
Alignment
