Yaesu FT-857 FT-857D Final PA Unit RF Power Amplifier Board Tested Working Original Donor Pull

Original Yaesu Final PA Unit RF power amplifier circuit board removed from a Yaesu FT-857 / FT-857D series amateur radio transceiver.
This is a vintage original-equipment RF amplifier assembly intended for repair, restoration, and preservation of compatible Yaesu HF/VHF/UHF all-mode transceivers.
The PA Unit is a critical section of the transmitter responsible for RF power amplification and supporting transmitter circuitry. Depending on the exact board configuration, this assembly incorporates RF power transistors, driver circuitry, impedance-matching networks, transformers, inductors, filtering components, bias and control circuits, and associated semiconductor devices.
This original Yaesu board is especially valuable for technicians repairing radios with damaged RF power amplifier sections, failed output devices, damaged driver circuits, or other faults involving the transmitter PA assembly.
ORIGINAL TRANSCEIVER TECHNICAL SPECIFICATIONS:
Manufacturer: Yaesu Musen Co., Ltd.
Equipment Family: FT-857 / FT-857D
Radio Type: Compact HF/VHF/UHF All-Mode Amateur Transceiver
Supported Amateur Bands: HF, 50 MHz, 144 MHz, 430 MHz
Supported Operating Modes: SSB, CW, AM, FM
Nominal Radio DC Supply: 13.8V
FT-857D Transmitter Output Ratings:
HF Amateur Bands: Up to 100W
50 MHz Amateur Band: Up to 100W
144 MHz Amateur Band: Up to 50W
430 MHz Amateur Band: Up to 20W
These are published transceiver specifications and do not represent individually measured output power from the supplied donor board.
ASSEMBLY CHARACTERISTICS:
Assembly Type: RF Final Power Amplifier Unit
Construction: Multi-component printed circuit board assembly
Component Technology: Discrete RF semiconductors, surface-mount components, through-hole components, RF magnetic devices, and associated circuitry
Intended Application: Original-equipment radio repair and restoration
Physical Condition: Previously installed donor assembly with visible evidence of use
Installation Requirements: Qualified electronic repair experience, correct mechanical mounting, connector verification, thermal management, and transmitter alignment
Exact PCB revision, assembly number, and regional configuration must be confirmed from the physical board before ordering.
HISTORICAL BACKGROUND:
Yaesu Musen was founded in Japan in 1956 and became one of the internationally recognized manufacturers of amateur radio communication equipment.
The FT-857 family emerged during the early 2000s as part of Yaesu's development of compact, multiband, all-mode amateur transceivers.
The FT-857 and subsequent FT-857D combined HF, 6-meter, 2-meter, and 70-centimeter operation in an unusually compact mobile-radio platform. This design appealed to amateur operators who wanted extensive frequency coverage without maintaining separate radios for each band.
The FT-857D became particularly popular for mobile operation, portable communications, field stations, and compact amateur radio installations.
Supporting this compact multiband design required sophisticated RF power amplifier circuitry capable of operating across several widely separated frequency ranges.
The Final PA Unit is consequently one of the important assemblies in the radio's transmitter architecture.
As the FT-857D family has been discontinued, original replacement circuit boards and complete donor assemblies remain useful for technicians maintaining these radios.
Preserving original Yaesu PA assemblies supports the continued repair of equipment that would otherwise be difficult to restore when original board-level replacement parts become unavailable.
LIFECYCLE: DISCONTINUED