Sony (BA-4) KV-27V40

# Sony (BA-4) KV-27V40 CRT RGB mod

The Sony KV-27V40 is a 27" curved-screen CRT television released in 1999. Built on the BA-4 chassis, it is highly regarded by CRT enthusiasts for its rich colors, exceptional geometry, and deep black levels associated with late-90s premium "V-series" Trinitrons.

View full CRT details and more mod examples →open in new window

Instructions below should also apply to these models:

• Sony KV-27V40
• Sony KV-27V45
• Sony KV-27V65

# Table of Contents

# Contributors

Thank you to everyone who contributed to this guide:

• Kaz Packmanopen in new window — contributor, RGB mod and pictures
• The Funk Wagon Savannahopen in new window — contributor, Pictures

# CRT safety

READ THIS BEFORE CONTINUING

# Plan of attack

READ THIS TO PREPARE

# Manuals and Datasheets

• Sony KV-27V40 Service Manualopen in new window

# Specs

• Manufactured: Mexico (1999)
• Chassis: BA-4
• Jungle Chip: Sony CXA2061S
• OSD Chip: Mitsubishi M7273MF
• Screen Size: 27"
• Power: 140 W

# RGB mux diagram

Prepare the mux diagram. If you are building your own circuit, this diagram should help.

# Calculating the RGB external resistor value

Formula from our theory page!

Calcualted 910Ω for 0.7Vp-p. With didoe inline for RGB, you have to use 1kΩ

# Performing the mod

Now that you roughly know what needs to be done, prepare for the mod. Place the board on a comfortable place. Make sure you are not putting pressure on the flyback or other components. Taking out the chassis is fairly straight forward on this CRT. There are few wires that needs to be disconnected.

1. Degauss wire
2. Power wire
3. Ground wire attached to the neck board
4. Yoke deflection coil wire
5. Anode wire (this is the one with the rubber cap)
6. Left and right audio wires

Please remember that wires 1-5 are critical for the CRT to function and should not be omitted. Having any of these wires disconnected while powering up can damage the board and can have adverse effects.

Sometimes it can be overwhelming to see a large chassis. But, we are primarily going to focus on two areas.

Chassis from Sony 20S42 (BA-4D). BA-4 is a similar chassis.

• Area 1: This is where we are going to remove resistors and attach the R, G, B and blanking wires
• Area 2: This is where we are going to connect composite, audio L, R and ground wires

# STEP 1: Remove the following components

Zooming in on Area 1.

Remove the following components. RGB resistors to the ground. Please always measure and mark them, so that you know you are removing the correct partrs.

• R086 (680Ω) Red ground resistor
• R087 (680Ω) Green ground resistor
• R088 (680Ω) Blue ground resistor

# STEP 2: Add RGB inline diodes (optional, but recommended)

To reduce interference, it is recommended to add these inline diodes. You will be lifting one side of the R025, R026, R027 and add diodes.

KV-27V40 - Heat shrink was used in the middle one to avoid shorts.

KV-27V42 - Heat shrink was used in the middle one to avoid shorts.

KV-27S42 - Below picture shows before adding the diodes.

KV-27S42 - After adding diodes inline

Pay attention to the diode direction and how it was installed. This is extremely important. Otherwise, OSD will not work.

Also, adding didoes means you will need to use 1KΩ resistors on the RGB mux board.

# STEP 3: Connect RGBs, Blanking

Then attach the R, G, B and blanking wires to the respective legs of the diodes. Wires should be attached to the side closer to the jungle chip.

• R, G, B wires are red, green and blue respectively
• Thick blue wire here is used for internal blanking through the switch. If you are using the ribbon cable with external blanking, this would be the brown wire.

# STEP 4: Connect Sync and Audio

• Thick yellow wire is for sync (luma)
• Thick white wire is for S-Video detect
• Purple and black wires are for ground
• Grey wire is for right audio
• White wire is for left audio

Full board

# STEP 5: Disconnect the VM cable to reduce artificial sharpening

The Velocity Modulation (VM) connector can be found on the neck board. Disconnecting this is recommended to get the best picture quality from your RGB and YPbPr mods.

# STEP 6: Build your mux board

This mod uses the RGB mux board. This is optional, but will make your mod easier and stable. You can also create the circuit presented in the schematics above without the board. Please also checkout the mux calculatoropen in new window to play with your own values.

Compatible mux boards:

• RGB MUX BOARD KIT 1.4Copen in new window
• RGB MUX BOARD KIT 1.4Bopen in new window

Buy your RGB mux board kit

On this particular CRT, Kaz chose to not use the external blanking signal. Instead, a switch was used to blank. Therefore, the blanking resistor (R11) and diodes (R9) are not populated.

5V for blanking was tapped from this location. There are also other possible locations on the chassis where 5V can be tapped from.

# STEP 7: YPbPr mod

This mod uses the 3P3T switch for blanking between YPbPr and RGB

Remove 0.01uF caps C380, C381, C382 and populate C371, C372 and C373 with 0.01uF caps. It's convenient to just move these ground capacitors over to the empty spots.

YPbPr wiring on the chassis

To provide greater clarity, the following image illustrates the correct connections for the wires. This image was sourced from the Sony KV-27S42, but the concept remains consistent.

# STEP 8: Attach the female SCART connector to TV

Creating a SCART cutout and mounting it is an art. I have a dedicated section for it. How to create and mount a SCART female plug?

Depending on your CRT, you might need to find a good place to mount the SCART port.

Sony KV-27V40

Holes for an unused AV jack were used for YPbPr jacks for a factory look.

# Reducing interference

Sometimes you might notice micro interference in the video signals. This is expected. To reduce it, try the following.

• Use diodes in-line for RGB signal
• Make sure your blanking wire is connected after the diode that feeds into the chroma chip (see diagram)
• Try routing most of the cabling below the PCB
• Keep the ribbon cable short
• I really didn't find any difference in interference in using shielded vs non-shileded cables. Therefore, this is optional.

# Getting into the service menu

• Turn the set on and then put into standby
• Press the Display, 5, VOL + buttons in sequence
• Turn on the CRT and you should be in service mode
• Use buttons "1" and "4" on the remote control to navigate the service menu
• Use buttons "3" and "6" to adjust the selected data

# Pictures of the mod

# Games (KV-27V40)

Street Fighter II

Street Fighter II

Street Fighter II

Street Fighter II

# Set

Full back

Back label

# Pictures

# Reference Photos

See more photos and contributions →open in new window