Philips VP415/VP410 Front-Loader Module Replacement

Overview

The Philips VP415 Domesday LaserDisc player (as well as the VP410) uses a small module with in-built switches to control the loading and unloading of the disc tray.  The original Philips design uses two small plastic switches that are custom designed for the board.  The original design is a weak-point of the player and is prone to damage (especially if the player is transported).  As the original switches are custom Philips parts, it’s not possible to simply repair or replace the switches when they get damaged.

VP415/VP410 Front-Loader Module replacement

This project provides a complete replacement for the front-loader module using industrial Omron micro-switches which provide a superior solution to the original in terms of robustness.  The module is a drop-in replacement for the original and requires no alteration to the player.

Hardware

Schematic

The schematic for the front-loader replacement module is shown in the following diagram:

Philips VP415 Front-Loader Schematic

The design consists of 2 switches that detect when the tray is ready to be loaded and when the tray is loaded.  In addition, a simple H-bridge provides power to the loader motor based on the LMOT-L (load direction) and LMOT-R (eject direction) signals.  Additionally the H-bridge has a motor jam protection circuit that prevents damage to the H-bridge in the case where the tray becomes stuck.  The replacement design also includes a 600mA PTC (self resetting fuse) to protect the module – this replaces the NFR protection resistor present on the original design.

PCB Design

The following picture show the overview of the PCB design:

Philips VP415 Front-Loader PCB top

The PCB is designed to be professionally produced as a two-layer board.  The following specifications are recommended:

  • Layers: 2
  • PCB Thickness: 1.6mm
  • PCB Colour: Green
  • Surface Finish: HASL
  • Copper Weight: 1oz
  • Material Details: FR4-Standard Tg 140C

Bill of Materials

The required materials are shown in the following table:

Ref Quantity Value Footprint Description
C101 1 47uF Capacitors_SMD:CP_Elec_6.3×7.7 Polarised capacitor
C102 1 4u7 Capacitors_SMD:CP_Elec_4x5.3 Polarised capacitor
D101, D102 2 SS16 Diodes_SMD:D_SMA Schottky diode
D103, D104, D105 3 1N4148W Diodes_SMD:D_SOD-123 Diode
F101 1 600mA Polyfuse Fuse_Holders_and_Fuses:Fuse_SMD2920 resettable fuse, polymeric positive temperature coefficient (PPTC)
J101 1 Drive Processor Lumberg-25-MSF:Lumberg-25-MSF-08 Generic connector, single row, 01×08
J102 1 Loader Motor Lumberg-25-MSF:Lumberg-25-MSF-03 Generic connector, single row, 01×03
Q101, Q102, Q103 3 BC848C TO_SOT_Packages_SMD:SOT-23 45V Vce, 0.8A Ic, NPN, SOT-23
Q104, Q106 2 BC327-25 TO_SOT_Packages_THT:TO-92_Molded_Narrow 45V Vce, 0.1A Ic, PNP Small Signal Transistor, TO-92
Q107, Q105 2 BC337-25 TO_SOT_Packages_THT:TO-92_Molded_Narrow 45V Vce, 0.1A Ic, NPN, Small Signal Transistor, TO-92
R102, R104, R105 3 10K Resistors_SMD:R_1206 Resistor
R103, R106 2 2K2 Resistors_SMD:R_1206 Resistor
R107, R109, R108, R110 4 750R Resistors_SMD:R_1206 Resistor
SW101, SW102 2 Omron D2HW-BR221DR D2HW-BR221DR:D2HW-8BR221DR Switch, single pole double throw

Fitting instructions

The board is fitted to the player using the two original screws and washers located at the back-right of the upper-deck.  The two mounting holes are elongated to allow the board to be moved; this causes the switches to activate sooner if required (by moving the board right) or later (by moving the board left).  If the loader motor continues to rotate once the tray is ejected, move the board to the left slightly.

Before powering up the player to test, move the tray in and out manually and ensure that the board (and components) are clear of any moving parts of the loader mechanism.

Files for download

The KiCAD files for the replacement board can be found in the Github repository along with the Gerber files required for PCB manufacture:

Philips VP415 Front-Loader repository