Yaesu FT-7900E - 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

Block Diagram

MAIN Unit Block Diagram

Block diagram illustrating the MAIN Unit of the transceiver.

PANEL Unit Block Diagram

Block diagram illustrating the PANEL Unit of the transceiver.

CH Unit Block Diagram

Block diagram illustrating the CH Unit of the transceiver.

Circuit Description

VHF Reception Circuit

Detailed explanation of the VHF reception signal path.

UHF Reception Circuit

Detailed explanation of the UHF reception signal path.

IF and Audio Circuits

Description of the Intermediate Frequency and audio circuits.

VHF Transmit Signal Path

Explanation of the VHF transmit signal path.

Circuit Description (Continued)

UHF Transmit Signal Path

Explanation of the UHF transmit signal path.

Alignment Procedures

Introduction and Precautions

Introduction and precautions before performing alignment.

Required Test Equipment

Alignment Procedures (Continued)

Alignment Preparation & Precautions

TX Power Output Alignment

Procedure for aligning transmit power output levels.

DCS TX Deviation Alignment

Entering the Alignment Mode

TX Deviation Alignment

Procedure for aligning transmit deviation settings.

CTCSS TX Deviation Alignment

PLL Reference Frequency Alignment

Exiting Alignment Mode

RF Front-end Tuning Alignment

Yaesu FT-7900E Specifications

General

Mode	FM
Power Output	50W (VHF), 35W (UHF)
Power Supply	13.8V DC
Antenna Impedance	50 Ohms
Memory Channels	1000
Channel Capacity	1000 channels
Channel Steps	5 kHz, 10 kHz, 12.5 kHz, 15 kHz, 20 kHz, 25 kHz
Frequency Range	144-146 MHz / 430-440 MHz