Philips VP406 LaserDisc Player Repair

Philips VP406 Repair
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Primary Contact	Aaron / Tim
Created	2025-03-26
Completed	{{{completeddate}}}
Dormant	{{{dormantdate}}}
Version	{{{version}}}
Members	Tim, JonW, Ali, Olivia, Aaron
Manufacturer	{{{manufacturer}}}
Model	{{{model}}}
Location	[[{{{location}}}]]
GitHub / Repo	{{{repo}}}
Status	{{{status}}}
Type	Undefined
Live Status	{{{livestatus}}}
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We're trying to fix a VP406 LaserDisc player. It lived under Tim's bed for many years and now we want to watch LaserDiscs during film night - but first, we must repair it. While the disc plays, and the TV syncs correctly, the video is offset. The issue appears to be before or around the PAL demodulator, since the on screen debugging menu is correctly positioned.

Resources

OCRd Service Manual for VP406 Player

Service manual for VP415 Player, pages 20-35 describe sending 'F-Codes' over RS232 to control things like 'jump to frame and freeze' which might be useful for getting a test pattern.

Schematics

Ali has combined and cleaned up the scematics from the service manual. Much nicer! The wiki won't make thumbnails for them because they're chonky, but you can click through to the original file.

• Aa - TXT Bypass, PAL Demodulator, Luminance Delay, Colour Transient Improver, U/V Processing, RGB Matrix
• Ab - Slave Source, Focus, Focus Drive, Sandcastle Generator, Sync Insert, Vertical Blanking Insert
• B - Radial Drive, Time Base Correction (TBC), Audio CCD, Variable Delay Line, Delay Control, Video CCD
• Ca - HF Processing, Video Demodulation, Dropout Correction,
• Cb - Audio Processing, Slide Drive
• Da - Special Burst Separator, "Reference"
• Db - Sequencing
• F - Power Supply
• N-P - Front Panel Keys
• SRa - Control, Watchdog, RS232
• SRb - CPU, SBUS
• Z - Laser Supply, Servo Pre-Amplifier, Tilt Motor Control

Timeline

26th March 2025

• Video plays, but is offset
• Power switch doesn't work - removed and bridged temporarily
• X2 RIFA capacitor exploded - removed

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29th March 2025

• Removed the other X2 capacitor, since it was probably also going to explode.
• Lots of debugging. We think the issue is not with Board A but Board D, which presumably creates a line pulse but out of phase from the video.
• Confirmed that the video feed going into the PAL modulator is alight, since the TV can sync to it.

What we want to check next:

• Verify that HMANCH is being generated correctly by probing CVTBM and HMANCH at the same time (see page 44 of schematic). They should line up.
• Check that HMANCH isn't being inverted in some weird way by the "SLAVE SOURCE" (see page 34)

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