Harman/Kardon Model 430 AM/FM/Stereo FM Solid State Receiver

Precautions

This section details critical safety and operational precautions for working with the Harman/Kardon Model 430 receiver:

• Always disconnect the power line before soldering to prevent transistor damage from power line leakage.
• Ensure power supply filter capacitors are discharged before performing any work on transistor amplifiers.
• Replace output and driver transistors with units from the same beta group.
• If an output transistor fails, check all output transistors and related bias circuitry in that channel before replacement to prevent further damage.
• Ensure the mounting surfaces of replacement power transistors (flange, mica insulators, heat sink) are clean to prevent transistor failure.
• Apply silicon grease between the transistor, mica insulator, and heat sink for optimal heat conduction.
• Always use fuses of the specified size and type to avoid component damage from excessive current.

Replacement Parts Ordering Note:

To expedite orders, include the model and serial numbers, quantity, part number, and description. Orders are processed on a cash-in-advance basis. Harman-Kardon reserves the right to substitute equivalent parts. Parts should be ordered from Harman-Kardon, 55 Ames Court, Plainview, N.Y. 11803, Attn: Parts Department.

System Overview and Diagrams

The document includes several diagrams illustrating the receiver's architecture and functionality:

• System Interconnection Diagrams: Block diagrams showing signal flow and module connections from inputs (AM ANT, PHONO, AUX, TAPE IN) through various stages (Tuner, Equalizer Amp, Tone/Preamp, Main Amp) to speaker outputs.
• Multivoltage System Interconnection Diagrams: Similar to the system interconnection diagrams but tailored for different voltage configurations.
• Wiring Diagrams: Detailed diagrams illustrating internal wiring, including color coding, for standard and multivoltage configurations, showing connections between components and boards.
• Stringing Diagram: Illustrates the correct routing of the dial cord for the tuning mechanism.

Alignment Procedures

Detailed procedures are provided for aligning the receiver's tuning and signal processing circuits:

• AM Alignment: Steps for optimizing AM reception using specific signal generators and test equipment, adjusting components like T251, T252, L252, TC55, TC54.
• FM Alignment: Steps for optimizing FM reception, including stereo performance, using signal generators and test equipment, adjusting components like T52, T202, R226, L52, TC53, L51, T51, TC52, TC51.
• MPX Alignment: Procedures for aligning the Multiplex stereo decoding circuitry, involving adjustments to VR301 and VR302.
• Tuning Indicator Adjustment: Steps to calibrate the tuning indicator.

Component Identification and Lists

The manual provides extensive information for identifying and sourcing components:

• PC Board Component Layouts: Diagrams showing the physical placement of components on various printed circuit boards, including the AM/FM Tuner/IF/MPX board, Main Amplifier board, Equalizer Amplifier board, Mode/Control Switch boards, Tone/Preamp board, and Rectifier boards.
• FM Front End Schematic: A detailed circuit schematic for the FM front end.
• Parts Lists: Comprehensive lists for the AM/FM Tuner/IF/MPX board, Main Amplifier board, Equalizer Amplifier board, Mode/Control Switch boards, Tone/Preamp board, Rectifier boards, and a Miscellaneous Parts List. These lists detail components such as resistors, capacitors, transistors, ICs, diodes, switches, fuses, transformers, knobs, and more, along with their Harman/Kardon part numbers and descriptions.

Performance Data and Troubleshooting Aids

• Voltage Chart: A table listing voltage measurements at various test points under specified conditions (AC120V, minimum volume, center tone, no signal, chassis ground). This includes readings for transistors and ICs in different sections (e.g., Tuner, Main Amp, Tone/Control).
• Schematic Diagrams: Detailed circuit schematics for all major functional blocks of the receiver, providing a comprehensive view of the electronic design for troubleshooting and repair.
• Internal Views (Photos): Labeled photographic views of the receiver's bottom and top sides, identifying major components and their locations, aiding in physical inspection and component identification.