Yokogawa PT70 PT900 Autopilot PCB/PWB & Spare Parts
YOKOGAWA DENSHIKIKI CO., LTD.
Refurbished
Manufacturer: Yokogawa Denshikiki Co., Ltd. / YDK
Product Type: Marine Autopilot / Heading Control System
Models Covered: PT70, PT900, PT900A, PT900D
Marine Application: Automatic and manual steering control for commercial vessels
Yokogawa PT70 and PT900 are different generations of marine autopilot systems. They should not be treated as the same equipment, and their PCB assemblies and internal spare parts should not be mixed.
For shipowners, technical managers and marine engineers, however, both systems present a similar sourcing problem: a complete autopilot normally does not need to be replaced when a single electronic board, feedback device, control module, encoder or steering component fails.
SM MARINE SERVICE™ supports identification and sourcing of Yokogawa autopilot equipment from the complete system level down to individual PCB/PWB assemblies, control modules, rotary encoders, rudder feedback devices and steering-related components.
For accurate identification, the model of the autopilot, unit model, PCB number, nameplate information and clear photographs should be checked before supply.
The Yokogawa PT70 is an earlier-generation marine autopilot system used on commercial vessels with different steering configurations.
Important equipment associated with the PT70 family includes:
The exact installed configuration can vary according to the vessel and steering arrangement.
The MPB351 Auto Steering Unit is one of the important control units associated with the PT70 system.
One confirmed service component relationship is:
Yokogawa PT70 → MPB351 Auto Steering Unit → V8814WP Rotary Encoder
The Yokogawa V8814WP Rotary Encoder is documented for MPB351 as well as earlier PB343/PB344 steering-unit applications.
A vessel searching only for:
V8814WP
Yokogawa V8814WP
MPB351 Rotary Encoder
PT70 Rotary Encoder
may therefore be looking for a relatively small internal component rather than a complete PT70 autopilot.
The PT70 steering system uses rudder-feedback equipment to provide actual rudder-angle information to the steering-control system.
Yokogawa μ-Transmitters and potentiometer-based feedback components are therefore particularly important when troubleshooting problems such as unstable rudder indication, incorrect feedback, steering deviation or loss of follow-up steering.
A documented service relationship also associates:
Yokogawa 1G162C015-01 Potentiometer
with PT120/PT123/PT111 and related feedback/actuator applications. However, the exact transmitter or actuator configuration installed onboard should always be confirmed before replacement.
Another documented PT70 spare relationship is:
Yokogawa PT70 → MKR051/MKR056 Steering Repeater Compass → V8820DE Dimmer
The V8820DE can therefore be relevant when sourcing components for the steering repeater/indication section rather than the main autopilot processor itself.
The PT900 is a later Yokogawa marine autopilot platform with modular control, display, steering, annunciation, navigation-interface and main-control electronics.
The PT900 family includes different control versions. Yokogawa specifications distinguish the PT900A Adaptive Control Type and PT900D PID Control Type. The system can also be configured for different steering-gear control arrangements, so the exact system code should be checked before determining PCB compatibility.
The MPH490 AP CDU is one of the most important operator/control assemblies in the PT900 system.
The PT900 component list identifies the following internal parts:
Yokogawa V8225AD — SH CPU Board Assembly
Yokogawa V8225AF / V8225AG / V8225AH — SH CPU Board Assembly variants
Yokogawa V8225HC — CDU Sub Board Assembly
Yokogawa V8225HD — Encoder Assembly
These exact component relationships are listed in the PT900 manual's component section.
Therefore a customer searching for Yokogawa V8225AD, for example, may actually require an internal CPU board for a PT900 MPH490 rather than the complete autopilot control stand.
The PT900 MPB390 Hand Steering Unit contains several separately identifiable electronic assemblies:
Yokogawa V8225DC — Hand CPU Board Assembly
Yokogawa V8225DH — Hand LED Board Assembly
Yokogawa V8225DE — Hand BZ Board Assembly
The component list also identifies an encoder and a V8225DP VR Assembly within the MPB390.
Possible sourcing searches therefore include:
Yokogawa V8225DC Hand CPU Board
Yokogawa V8225DH Hand LED Board
Yokogawa V8225DE MPB390
Yokogawa MPB390 PCB
For Non-Follow-Up steering, the PT900 uses the MPB391 NFU Lever.
Its documented internal electronic component includes:
Yokogawa V8225GE — Switch B.L. Board Assembly
This makes V8225GE, MPB391 PCB, PT900 NFU Lever PCB and similar terms useful exact-component searches.
The PT900 alarm and indication system includes the MPH690 Annunciator Unit.
Documented PCB assemblies include:
Yokogawa V8225BC — Annunciator Board Assembly
Yokogawa V8225BE — Annunciator Board Assembly
These should be identified against the installed configuration/revision before replacement.
The MPT590 NAV I/F Unit handles navigation-related system interfacing.
Its principal documented board is:
Yokogawa V8225FT — NAV I/F Board Assembly
The PT900 circuit documentation shows the NAV interface as part of the system's interconnected electronics.
For procurement searches, useful relationships include:
Yokogawa PT900 MPT590
Yokogawa V8225FT
Yokogawa V8225FT NAV I/F PCB
PT900 Navigation Interface Board
The MPH291 Main Control Unit (MCU) contains some of the most important PT900 PCB assemblies.
The PT900 component list identifies:
Yokogawa V8225AM — Main Power Board Assembly
Yokogawa V8225AS — Secondary Power Board Assembly
Yokogawa V8225BQ / V8225BU / V8225BS — Manual Terminal Board Assemblies
Yokogawa V8225FC / V8225FF — CAN Adapter Board Assemblies
Yokogawa V8225BG — Annunciator Interface Board Assembly
These relationships are particularly valuable when troubleshooting a PT900 that has a localized power, communication, manual-steering or annunciator-interface problem.
The PT900 MPH790 System Selector contains:
Yokogawa V8225GC — Switch B.L. Board Assembly
The selector is part of the bridge-side control architecture and should not be confused with the main CPU/CDU electronics.
The MPH791 Mode Selector includes:
Yokogawa V8225EC — CPU Board Assembly
Yokogawa V8225EF — Interface Board Assembly
These components provide another important exact-part-number sourcing route for vessels repairing the PT900 rather than replacing the complete selector assembly.
The Yokogawa V8223FP Servo Control Board is especially important because it connects directly with the steering-control and rudder-feedback side of the autopilot.
PT900 adjustment documentation identifies:
CONTROL STAND SERVO CONTROL BOARD — V8223FP
The circuit documentation shows rudder-order and rudder-feedback signals entering this steering-control circuitry. It also identifies adjustment points for feedback zero/span and steering response.
For technical sourcing, important search relationships include:
Yokogawa V8223FP Servo Control Board
Yokogawa PT900 V8223FP
PT900 Servo Control PCB
PT900 Rudder Feedback PCB
The PT900 steering architecture uses feedback from the steering gear to determine actual rudder position.
The system architecture includes μ-Transmitters associated with steering channels, with feedback signals returning from the steering gear side to the autopilot control system.
In applicable configurations, the MPT123A μ-Transmitter uses a potentiometer-based mechanism to provide rudder feedback.
The V8223FP adjustment documentation specifically shows the μ-Transmitter potentiometer feedback signal entering the servo-control circuitry and provides zero/span adjustment points.
Typical faults in this area can therefore involve:
A technician should diagnose the actual cause before replacing components.
On an operating vessel, failure of one PCB does not necessarily mean that the complete Yokogawa autopilot system has failed.
For example:
PT900 → MPH490 → V8225AD CPU Board
PT900 → MPT590 → V8225FT NAV I/F Board
PT900 → MPH291 → V8225AM Main Power Board
PT900 → MPB390 → V8225DC Hand CPU Board
PT900 → MPH791 → V8225EC CPU Board
PT900 → Servo Control → V8223FP
A superintendent or marine electronics engineer may therefore search only the number printed on the defective PCB.
This is why SM MARINE SERVICE™ identifies Yokogawa autopilot spare parts by system model, equipment model, PCB/PWB number, function and installed configuration.
PT70 and PT900 belong to different Yokogawa autopilot generations.
A PT70 component should not be assumed to be interchangeable with a PT900 component merely because both systems perform the same steering function.
For example:
PT70 MPB351 → V8814WP Rotary Encoder
while the PT900 MPH490 uses its own documented encoder assemblies and V8225-series electronics.
Always verify the equipment model, board number, connector arrangement, revision and vessel steering configuration before ordering.
Check the MPH490 CDU, CPU board, CDU Sub Board, encoder, power supply and relevant communication circuits.
Inspect the MPB390 and associated V8225DC, V8225DH and V8225DE electronics, together with encoder/VR components and external wiring.
Check MPB391, V8225GE, steering command circuits, terminal connections and downstream steering-control equipment.
Inspect external sensor/data sources, cabling and the MPT590 NAV Interface Unit including V8225FT where applicable.
Check MPH690, V8225BC/V8225BE and the V8225BG annunciator-interface section in the MCU.
Inspect the μ-Transmitter, potentiometer, mechanical linkage, wiring, zero/span calibration and servo-control circuitry including V8223FP where fitted.
Check vessel input supply, protection devices and the MPH291 power section including V8225AM and V8225AS according to the installed configuration.
PT900 systems are available in different configurations.
Yokogawa documentation distinguishes PT900A Adaptive and PT900D PID control types and multiple steering-gear control arrangements, including solenoid-valve, hydraulic and continuous-control configurations.
Therefore, when requesting a PT900 PCB or spare part, please provide:
This helps prevent incorrect supply when different PT900 configurations use different electronics.
SM MARINE SERVICE™ supports sourcing and technical identification for Yokogawa/YDK marine autopilot equipment, including:
PT70 and PT900 complete units, PCB/PWB assemblies, CPU boards, power boards, terminal boards, interface boards, CAN boards, annunciator boards, selector electronics, servo-control boards, rotary encoders, μ-Transmitters, rudder-feedback components, potentiometers, steering-control units and other available marine autopilot spare parts.
Support can be arranged for shipowners, ship managers, technical departments, marine service companies, shipyards and vessel operators worldwide.
Yes, when the defective PCB can be correctly identified and a compatible serviceable replacement is available. The exact board number and installed configuration should be confirmed first.
V8225AD is documented as an SH CPU Board Assembly used within the PT900 MPH490 Autopilot Control & Display Unit.
V8225FT is the documented NAV I/F Board Assembly for the PT900 MPT590 NAV Interface Unit.
V8225AM is the Main Power Board Assembly documented within the PT900 MPH291 Main Control Unit.
V8223FP is identified in PT900 technical documentation as a Servo Control Board used in steering-control and rudder-feedback circuitry.
V8814WP is documented as a rotary encoder associated with PB343, PB344 and MPB351, making it relevant to the PT70 MPB351 Auto Steering Unit.
They should not be assumed interchangeable. They are different autopilot generations and the exact equipment model, PCB number, revision and steering configuration must be verified.
For Yokogawa PT70 or PT900 autopilot spare-part inquiries, send the equipment nameplate, PCB/PWB number, clear photographs and required quantity.
SM MARINE SERVICE™
Marine Automation, Navigation & Communication Equipment and Spare Parts
Chattogram, Bangladesh
China Support: Shanghai
Email: info@smmarineservice.com
Mobile / WhatsApp / Viber: +8801818929292
Website: www.smmarineservice.com
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