Yaesu FT-7900R/E - User Manual

FT-7900R/E Technical Supplement
Dual Band FM Transceiver
FT-7900R/E
Technical Supplement
Introduction
This manual provides technical information necessary for servicing the FT-7900R/E Transceiver.
Servicing this equipment requires expertise in handling surface-mount chip components. Attempts by non-qualified
persons to service this equipment may result in permanent damage not covered by the warranty, and may be illegal in
some countries.
Two PCB layout diagrams are provided for each double-sided circuit board in the transceiver. Each side of thr board is
referred to by the type of the majority of components installed on that side (“leaded” or “chip-only”). In most cases one
side has only chip components, and the other has either a mixture of both chip and leaded components (trimmers, coils,
electrolytic capacitors, ICs, etc.), or leaded components only.
While we believe the technical information in this manual to be correct, Vertex Standard assumes no liability for dam-
age that may occur as a result of typographical or other errors that may be present. Your cooperation in pointing out any
inconsistencies in the technical information would be appreciated.
Specifications ................................................ A-1
Exploded View & Miscellaneous Parts ..... B-1
Block Diagram................................................C-1
Circuit Description ....................................... D-1
Alignment ....................................................... E-1
Contents
Board Unit (Schematics, Layouts & Parts)
MAIN Unit ................................................. F-1
PANEL Unit ............................................. G-1
CH Unit ..................................................... H-1
©
2011 VERTEX STANDARD CO., LTD. EH016M93B
Important Note
The transceiver was assembled using Pb (lead) free solder, based on the RoHS specification.
Only lead-free solder (Alloy Composition: Sn-3.0Ag-0.5Cu) should be used for repairs performed on this appara-
tus. The solder stated above utilizes the alloy composition required for compliance with the lead-free specifica-
tion, and any solder with the above alloy composition may be used.
VERTEX STANDARD CO., LTD.
4-8-8 Nakameguro, Meguro-Ku, Tokyo 153-8644, Japan
VERTEX STANDARD
US Headquarters
10900 Walker Street, Cypress, CA 90630, U.S.A.
YAESU UK LTD.
Unit 12, Sun Valley Business Park, Winnall Close
Winchester, Hampshire, SO23 0LB, U.K.
VERTEX STANDARD HK LTD.
Unit 1306-1308, 13F., Millennium City 2, 378 Kwun Tong Road,
Kwun Tong, Kowloon, Hong Kong
VERTEX STANDARD
(
AUSTRALIA
)
PTY., LTD.
Tally Ho Business Park, 10 Wesley Court, East Burwood, VIC, 3151

Summary

Specifications

Block Diagram Overview

MAIN Unit Block Diagram

Circuit Description

Reception Circuits

Details VHF and UHF reception paths, IF, audio processing, and squelch control.

Transmit Signal Path

Describes signal flow for VHF/UHF transmission, including APC, PTT, and PLL circuits.

Alignment Procedures

Alignment Introduction and Precautions

Guidelines and warnings for performing transceiver alignment procedures.

Required Test Equipment

List of essential test equipment needed for accurate alignment.

Alignment Mode Entry and Preparation

Steps to enter alignment mode and prepare the transceiver for adjustments.

PLL Reference Frequency Alignment

Procedure to set the PLL reference frequency accurately.

RF Front-end Tuning

Steps for tuning the RF front-end for optimal signal reception.

TX Power Output Alignment

Procedure to set and verify transmit power levels across different bands.

TX Deviation Alignment

Procedure to set and verify transmit frequency deviation.

DCS and CTCSS TX Deviation

Meter Sensitivity and DC Voltmeter Alignment

Closing Alignment Mode

MAIN Unit Details

MAIN Unit Circuit Diagram

PANEL Unit Details

PANEL Unit Circuit Diagram

Yaesu FT-7900R/E Specifications

General

Power Output	50W (VHF), 35W (UHF)
Modes	FM
Power Supply Voltage	13.8V DC ±15%
Antenna Impedance	50 Ω
Operating Temperature	-20°C to +60°C
Receiver Sensitivity	0.2 µV (12 dB SINAD)
Channel Steps	5/10/12.5/15/20/25 kHz