Yaesu FT-7800R Service Manual

Dual Band FM Transceiver

FT-7800R

Technical Supplement

2003 VERTEX STANDARD CO., LTD. (EH016M90A

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 EUROPE B.V.

P.O. Box 75525, 1118 ZN Schiphol, The Netherlands

YAESU UK LTD.

Unit 12, Sun Valley Business Park, Winnall Close Winchester, Hampshire, SO23 0LB, U.K.

VERTEX STANDARD HK LTD.

Unit 5, 20/F., Seaview Centre, 139-141 Hoi Bun Road,

)

Kwun Tong, Kowloon, Hong Kong

Introduction

This manual provides technical information necessary for servicing the FT-7800R 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 damage 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.

Contents

Specifications ................................................ A-1

Exploded View & Miscellaneous Parts ..... B-1

Block Diagram ................................................C-1

Circuit Description ....................................... D-1

Alignment ....................................................... E-1

Board Unit (Schematics, Layouts & Parts)

MAIN Unit ................................................. F-1

PANEL Unit ............................................. G-1

CH Unit ..................................................... H-1

Specifications

General

Frequency Range: RX: 108.000 - 520.000 MHz,

700.000 - 999.995 MHz (Cellular Blocked)

TX: 144.000 - 148.000 MHz or 144.000 - 146.000 MHz,

430.000 - 450.000 MHz or 430.000 - 440.000 MHz

Channel Steps: 5/10/12.5/15/20/25/50/100 kHz Modes of Emission: F3E, F2D, F2A Antenna Impedance: 50 Ohms, unbalanced (Antenna Duplexer built-in) Frequency Stability: ±5 ppm @ 14 °F ~ +140 °F (–10 °C ~ +60 °C) Operating Temperature Range: –4 °F ~ +140 °F (–20 °C ~ +60 °C) Supply Voltage: 13.8 VDC (±15 %), negative ground Current Consumption (Approx.): RX: 0.5 A (Squelched)

TX: 8.5 A

Case Size (W x H x D): 5.5” x 1.6” x 6.6” (140 x 41.5 x 168 mm) (w/o knobs & connectors) Weight (Approx.): 2.2 lb. (1 kg)

Transmitter

Output Power: 50/20/10/5 W (144 MHz)

40/20/10/5 W (430 MHz)

Modulation Type: Variable Reactance Maximum Deviation: ±5 kHz Spurious Radiation: At least –60 dB below Microphone Impedance:2 kΩ DATA Jack Impedance: 10 kΩ

Receiver

Circuit Type: Double-conversion superheterodyne Intermediate Frequencies: 45.05 MHz/450 kHz Sensitivity: 0.8 µV (TYP) for 10 dB SN (108 - 137 MHz, AM)

0.2 µV for 12 dB SINAD (137 - 150 MHz, FM)

0.25 µV for 12 dB SINAD (150 - 174 MHz, FM)

0.3 µV (TYP) for 12 dB SINAD (174 - 222 MHz, FM)

0.25 µV (TYP) for 12 dB SINAD (222 - 300 MHz, FM)

0.8 µV (TYP) for 10 dB SN (300 - 336 MHz, AM)

0.25 µV for 12 dB SINAD (336 - 420 MHz, FM)

0.2 µV for 12 dB SINAD (420 - 520 MHz, FM)

0.4 µV (TYP) for 12 dB SINAD (800 - 900 MHz, FM)

0.8 µV (TYP) for 12 dB SINAD (900 - 999.99 MHz, FM)

Squelch Sensitivity: Better than 0.16 µV Selectivity (–6dB/–60dB): 12 kHz/30 kHz Maximum AF Output: 2 W @ 8 Ω for 10% THD AF Output Impedance: 4-16 Ω

Specifications are subject to change without notice, and are guaranteed within the 144 and 430 MHz amateur bands only. Frequency ranges will vary according to transceiver version; check with your dealer.

A-1

Exploded View & Miscellaneous Parts

SCREW LIST

No. VXSTD P/N DESCRIPTION QTY.

 U31208007 OVAL HEAD SCREW M2.6X8B 8  U44308002 TAPTITE SCREW M3X8NI 17  U03310002 SEMS SCREW ASM3X10NI 4  U20308002 BINDING HEAD SCREW M3X8NI 2  U25320007 TAPTITE SCREW M3X20B 4  U23116007 TAPTITE SCREW M2X16B 5  U31206007 OVAL HEAD SCREW M2.6X6B 6

SUPPLIED ACCESSORIES

VXSTD P/N DESCRIPTION

Q0000081 FUSE 15A (x2 pcs)

AAA43X001 MIC MH-48A6J

T9021715 DC CABLE

R8139500 LABEL

RA02132A0 HIMERON TAPE

M4090149 SPEAKER

R0150630 HOLDER

T9206438A WIRE ASSY

RA0322600 RUBBER SHEET

MAIN UNIT

RA02668AA CHASSIS









































 

CS1804001 CASE (W/ NYLON NET)



R8139500 LABEL

RA0415200 (x2 pcs) GROUND PLATE



M2090034A FAN

T9206876 WIRE ASSY



RA0552200 LCD SPACER

RA0539900 RUBBER KNOB

RA0541400 FRONT PANEL ASSY (W/ WINDOW, DOUBLE FACE TAPE)

RA0540200 KNOB

RA0540100 ENCODER KNOB

RA0551900 REFLECTOR SHEET

RA0551800 DIFFUSER SHEET

RA0540800 LCD HOLDER

PANEL UNIT

RA0022900 COIL SPRING

RA0540400 RELEASE KNOB

RA0540300 KNOB

T9101536 CT CABLE



Q9000804 ROTARY ENCODER (W/ HEX NUT*, WASHER*)

RA0540900 INTER CONNECTOR

RA0540700 LIGHT GUIDE

G6090155 LCD

RA0438700 RUBBER





CH UNIT

P1091107 CONNECTOR





RA0551700 REAR PANEL ASSY (W/ COIL SPRING, RELEASE KNOB)

T9207057 WIRE ASSY

RA0539800 SUB PANEL

S5000206 FAN GUARD



P1090984 CONNECTOR (Ver: USA)

P1090547 CONNECTOR (Ver: EXP, AUS)

S5000236 WASHER (Ver: EXP, AUS)

Non-designated parts are available only

as part of a designated assembly.

B-1

Exploded View & Miscellaneous Parts

Note

B-2

Block Diagram

D-1

Block Diagram

Note

D-2

Circuit Description

VHF Reception

The incoming VHF signal is passed through a low-pass filter network, antenna switching diodes D1074 (RLS135), D1075 (RLS135) and D1015 (HVC131), and another low- pass filter network to the RF amplifier Q1008 (3SK296ZQ). The amplified RF signal is passed through a varactor controlled bandpass filter consisting of L1017, L1018, and D1010, D1011, and D1012 (all HVC365), then applied to the first mixer Q1009 (3SK296ZQ) along with the first local signal from the PLL circuit.

The first local signal is generated between 189.05 MHz and 193.05 MHz, depending on the receiving frequency, by the VHF VCO, which consists of Q1076 (2SC5374) and varactor diodes D1049 (HVC365), D1050 (HVC131), D1051 (HVC365), and D1052 (HVC362).

UHF Reception

The incoming UHF signal is passed through a low-pass filter network, antenna switching diodes D1077 (UM9401F) and D1018 (RLS135), D1019 (RLS135), and D1084 (HSC277), and another low-pass filter network to the RF amplifier Q1001 (3SK296ZQ). The amplified RF signal is passed through a varactor-controlled band-pass filter consisting of L1006 and L1007, and D1002, D1003, and D1004 (all HVC350B), then applied to the first mixer Q1002 (3SK296ZQ) along with the first local signal from the PLL circuit.

The first local signal is generated between 384.95 MHz and 404.95 MHz, depending on the receiving frequency, by the UHF VCO, which consists of Q1072 (2SC5006) and varactor diodes D1046 (HVC375B) and D1047 (HVC350B).

IF and Audio Circuits

The 45.05 MHz first IF signal is applied to the monolithic crystal filter XF1001 which strips away unwanted mixer products, and the IF signal is applied to the first IF amplifier Q1016 (2SC4400). The amplified first IF signal is then delivered to the FM IF subsystem IC Q1023 (TA31136FN), which contains the second mixer, limiter amplifier, noise amplifier, and FM detector.

The 44.6 MHz second local signal is derived from 11.15 MHz crystal X1002, the frequency of which is multiplied by four at Q1022 (2SC4400), producing the 450 kHz sec- ond IF signal when mixed with the first IF signal within Q1023 (TA31136FN).

The detected audio passes through the de-emphasis network, a low-pass filter consisting of Q1028 (NJM2902V) and associated circuitry, and a high-pass filter consisting of Q1028 (NJM2902V) and associated circuitry. The filtered audio signal is passed through the audio volume control IC Q1034 (M51132FP) which adjusts the audio sensitivity to compensate for audio level variations, then delivered to the audio switch Q1036 (DTC144EE).

Squelch Control

When no carrier received, noise at the output of the detector stage in Q1023 (TA31136FN) is amplified and bandpass filtered by the noise amp section of Q1023 (TA31136FN). The resulting DC voltage is applied to pin 2 of main CPU Q1065 (M3826AEFGP), which compares the squelch threshold level to that which set by the front panel SQL knob.

While no carrier is received, pin 53 of Q1065 (M3826AEFGP) remains “low,” to disable audio output from the speaker.

Transmit Signal Path

The speech signal from the microphone passes through the MIC jack J2001 to AF amplifier Q2011 (NJM2904V) on the PANEL unit. The amplified speech signal is subjected to amplitude limiting by Q1040 (NJM2902V) on the MAIN unit. The speech signal then passes through low-pass filter network Q1040 (NJM2902V) and band switch Q1039 (BU4066BCFV) to the VHF VCO or UHF VCO.

VHF Transmit Signal Path

The adjusted speech signal from Q1040 (NJM2902V) is delivered to VHF VCO Q1076 (2SC5374) which frequen- cy modulates the transmitting VCO made up of D1049 (HVC365). The modulated transmit signal passes through buffer amplifiers Q1077 and Q1078 (both 2SC5374). The amplified transmit signal is then applied to the Pre-Drive amplifier Q1084 (2SK2596) and Driver amplifier Q1086 (RD07MVS1), then finally amplified by Power amplifier Q1087 (RD70HVF1) up to 50 Watts. This three-stage pow- er amplifier’s gain is controlled by the APC circuit. The 50 Watt RF signal passes through high-pass filter and lowpass filter network, antenna switch D1072 and D1073 (both XB15A709A), and another low-pass filter network, and then is delivered to the ANT jack.

The 450 kHz second IF signal is applied to the ceramic filter CF1001 which strips away all but the desired shignal, and then passes through the limiter amplifier within Q1023 (TA31136FN) to the ceramic discriminator CD1001 which removes any amplitude variations in the 450 kHz IF signal before detection of speech.

D-1

Circuit Description

UHF Transmit Signal Path

The adjusted speech signal from Q1040 (NJM2902V) is delivered to UHF VCO Q1072 (2SC5006) which frequency modulates the transmitting VCO made up of D1046 (HVC375B). The modulated transmit signal passes through buffer amplifiers Q1073, Q1074, and Q1075 (all 2SC5006). The filtered transmit signal is then applied to the Pre-Drive amplifier Q1084 (2SK2596) and Driver amplifier Q1086 (RD07MVS1), then finally amplified by Power amplifier Q1087 (RD70HVF1) up to 40 Watts. This three-stage power amplifier’s gain is controlled by the APC circuit. The 40 Watt RF signal passes through highpass filter and low-pass filter networks, antenna switch D1077 (UM9401F), and another low-pass filter network, and then is delivered to the ANT jack.

TX APC Circuit

A portion of the power amplifier output is rectified by

D1070 and D1071 (UHF: D1078 and D1079, all MA2S728), then delivered to APC Q1081 (NJM2904V),

as a DC voltage which is proportional to the output level of the power amplifier. The APC Q1081 (NJM2904V) com- pares the rectified DC voltage from the power amplifier and the reference voltage from the main CPU Q1065 (M3826AEFGP), to produce a control voltage, which regulates supply voltage to the Pre-Drive amplifier Q1084 (2SK2596), Drive amplifier Q1086 (RD07MVS1) and Power amplifier Q1087 (RD70HVF1), so as to maintain stable output power under varying antenna loading conditions.

PTT Circuit

When the PTT switch is pressed, pin 8 of sub CPU Q2001 (M38223E) goes “high”, which send the “PTT” command to main CPU Q1065 (M3826AEFGP). When the CPU receives the “PTT” command, it engages Q1057 (UMA8N) and Q1058 (IMT17), which activates the Tx circuit.

PLL Circuit

A portion of the output from the VCO Q1076 (2SC5374) and Q1072 (2SC5006), passes through the programmable divider section of the PLL IC Q1070 (MB15A02PFV1), which divides the VCO frequency according to the frequency dividing data that is associated with the current frequency input from the main CPU Q1065 (M3826AEFGP). It is then sent to the phase comparator. The 11.15 MHz frequency of the reference oscillator circuit derived from X1002 is divided by the reference frequency divider section of Q1070 (MB15A02PFV1) into 4250 or 3400 parts to become 5 kHz or 6.25 kHz comparative reference frequencies, which are utilized by the phase comparator. The phase comparator section of Q1070 (MB15A02PFV1) compares the phase between the frequency-divided oscillation frequency of the VCO circuit and the comparative frequency and its output is a pulse corresponding to the phase difference. This pulse is integrated by the charge pump and loop filter of Q1070 (MB15A02PFV1) into a control voltage (VCV) to control the oscillation frequency of the VCOs.

D-2

Alignment

Introduction and Precautions

The FT-7800R has been carefully aligned at the factory for the specified performance across the 144 MHz and 430 MHz amateur bands. Realignment should therefore not be necessary except in the event of a component failure. All component replacement and service should be performed only by an authorized Vertex Standard representative, or the warranty policy may be voided.

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 are replaced, realignment 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 component has been replaced.

We recommend that servicing be performed only by authorized Vertex Standard service technicians who are experienced 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 must reserve the right to change circuits and alignment procedures in the interest of improved performance, without notifying owners.

Under no circumstances should any alignment be attempted unless the normal function and operation of the transceiver are clearly understood, the cause of the malfunction has been clearly pinpointed and any faulty components replaced, and the need for realignment determined to be absolutely necessary.

Required Test Equipment

The following test equipment (and thorough familiarity with its correct use) is necessary for complete realignment. 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 adjustments 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.

 Regulated DC Power Supply: adjustable from 11.5 to

16 VDC, 10 A

 RF Signal Generator with calibrated output level at

500 MHz

 Frequency Counter: ±0.1 ppm accuracy at 500 MHz  AF Signal Generator  SINAD Meter  Oscilloscope  Spectrum Analyzer  Deviation Meter (linear detector)  AF Millivoltmeter  AF Dummy Load: 8-Ohm, 5 W  DC Voltmeter: high impedance  Inline Wattmeter with 5% accuracy at 500 MHz  50-Ohm non-reactive Dummy Load: 50 watts at 500 MHz  VHF/UHF Sampling Coupler

Set up the test equipment as shown below, and apply 13.8 VDC power to the transceiver.

SINAD

Meter

8-ohm

Dummy Load

EXT SP

Power Supply

13.8 VDC

RF Signal Generator

RF Sampling

Coupler

Inline

Wattmeter

50-ohm

Dummy Load

Frequency

Counter

Pin 5

Deviation

Meter

AF Signal Generator

E-1

Alignment

Alignment Preparation & Precautions

A dummy load and inline wattmeter must be connected to the main antenna jack in all procedures that call for transmission, except where specified otherwise. Correct alignment is not possible with an antenna. After completing one step, read the following step to determine 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 in the repair shop be the same as that of the transceiver and test equipment, and that this temperature be held constant between 68 °C and 86 °F (20 °C ~ 30 °C). When the transceiver is brought into the shop from hot or cold air it should be allowed some time for thermal equalization with the environment before alignment. If possible, alignments should be made with oscillator shields and circuit boards firmly affixed in place. Also, the test equipment must be thoroughly warmed up before beginning.

Notes: Signal levels in dB referred to in alignment are

based on 0 dBµ = 0.5 µV (closed circuit).

Entering the Alignment mode

Alignment of the FT-7800R is performed using a frontpanel software-based procedure. To perform alignment of the transceiver, it must first be placed in the “Alignment Mode,” in which the adjustments will be made and then stored into memory.

To enter the Alignment mode:

1. Press and hold in the [MHz(PRI)] key and the Hyper Memory [5] key while turning the radio on. Once the radio is on, release these two keys.

2. Press the front panel keys in the following sequence. [

MHz(PRI)]  [TONE(HM/RV)] [LOW(ACC)] 

[

BAND(SET)]  [V/M(MW)] 

[

SCAN(SEL)]  [S.SCH(ARTS

3. Press and hold in the REF.xxH” to appear on the display, this signifies that the transceiver is now in the “Alignment mode.”

[ ]

key to cause “A-0

)]

PLL Reference Frequency

1. Tune the frequency to 435.050 MHz, then set the Transmit Power Level to “LOW.”

2. Press the [BAND(SET)] key while pressing and holding in the parameter to “A-0 REF.xxH.”

3. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding the

]

[

key, if needed, so that the counter frequency read-

ing is 435.050 MHz (±100 Hz).

[ ]

key, if needed, to set the Alignment

RF Front-end Tuning

1. Connect the DC voltmeter to TP1010 on the MAIN Unit, then inject a 439.050 MHz signal at a level of +10 dBµ (with 1 kHz modulation @±3.5 kHz deviation) from the RF Signal Generator.

2. Tune the frequency to 439.050 MHz.

3. Press the [BAND(SET)] key while pressing and holding the “A-1 TUN.xxH.”

4. Adjust the DIAL knob while pressing and holding in the reaches maximum deflection. The FT-7800R’s RF Front-end has a broad bandwidth. Therefore, prior to adjustment you must adjust the DIAL knob to set the frequency to the middle of the band, in step 2, so you can set peak in the DC voltmeter's deflection in the center of the RF passband.

5. Tune the frequency to 145.050 MHz.

6. Inject a 145.050 MHz signal at a level of +10 dBµ (with 1 kHz modulation @±3.5 kHz deviation) from the RF Signal Generator.

7. Adjust the DIAL knob while pressing and holding in the reaches maximum deflection. As in the previous section, be sure to set the DIAL knob for the center of the band prior to making this adjustment.

[ ]

key to set the Alignment parameter to

[ ]

key, if needed, so that the DC voltmeter

[ ]

key, if needed, so that the DC voltmeter

TP1010

E-2

MAIN UNIT TEST POINTS

Alignment

TX Power Output

1. Tune the frequency to 440.050 MHz, then set the Transmit Power Level to “LOW.”

2. Press the [BAND(SET)] key while pressing and holding in the “A-2 PWR.xxH.”

3. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 5 Watts (±0.5 Watt).

4. Increase the Transmit Power Level to “MID2.”

5. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 10 Watts (±0.5 Watt).

6. Increase the Transmit Power Level to “MID1.”

7. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 20 Watts (±0.5 Watt).

8. Increase the Transmit Power Level to “HIGH.”

9. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 40 Watts (±0.5 Watt).

10. Tune the frequency to 146.050 MHz, then set the Transmit Power Level to “LOW.”

11. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while press and holding the [%] key, as needed, so that the wattmeter reading is 5 Watts (±0.5 Watt).

12. Increase the Transmit Power Level to “MID2.”

13. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 10 Watts (±0.5 Watt).

14. Increase the Transmit Power Level to “MID1.”

15. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 20 Watts (±0.5 Watt).

16. Increase the Transmit Power Level to “HIGH.”

17. Press the PTT switch to activate the transmitter, and adjust the DIAL knob while pressing and holding in the is 50 Watts (±0.5 Watt).

[ ]

key to set the Alignment parameter to

]

[