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Sony KV (BA-4D)

Sony KV (BA-4D)

SuntharAbout 5 minCRT RGB modKV-13M42KV-20M42KV-20S90KV-20S42KV-27V42KV-27S42

Sony BA-4D chassis CRT RGB mod

If you're looking to get the most out of your Sony Trinitron, you may want to consider modding it for RGB output. This guide will show you how to do just that.

This is a fairly straightforward mod to perform. For CRTs that are larger than 20", it is recommended you use shielded RGB cables internally.

Below mod was performed on a Sony KV-20S90, by a reddit user /u/atomized69. I also performed a similar mod on KV-20S42. Instructions below should also apply to these models:

  • KV-13M42
  • KV-20M42
  • KV-20S42
  • KV-20S43
  • KV-20S90
  • KV-27S42
  • KV-27V42
  • KV-27S46
  • KV-27S66
  • KV-35S36


CRT safety


You can die doing this! So read carefully! CRT TV is not a toy. Do not open a CRT TV. If you don't have any prior knowledge about handling high voltage devices, this guide is not for you. CRT TV contains high enough voltage (20,000+ V) and current to be deadly, even when it is turned off.


Plan of attack



Sometimes it is nice to know the theory behind the mod. I have put this on a separate page. This shows how the various resistor values are calculated.


Service manuals


Sony KV-20S90

  • Manufactured: October 2001, Mexico
  • NTSC, 60 Hz - 95W
  • Chassis: BA-4D
  • Tube: A51LDG51X
  • Jungle Chip: CXA2133BS
  • OSD Chip: M37273MF-255SP

Sony KV-20S42

  • Manufactured: September 1999, Mexico
  • NTSC, 60 Hz - 90W
  • Chassis: BA-4D
  • Tube: A51LDG550X
  • Jungle Chip: CXA2061S
  • OSD Chip: M37273MF-255SP

Sony KV-27S42

  • Manufactured: September 1999, Mexico
  • NTSC, 60 Hz - 90W
  • Chassis: BA-4D
  • Tube: A68LML50X
  • Jungle Chip: CXA2133BS
  • OSD Chip: M37273MF-255SP


Sony BA-4D chassis schematics

Mux diagram

If you are building your own circuit, this diagram should help. The diagram is for KV-27S42, it will also work for KV-20S90, KV-20S42 or any other BA-4D chassis.

Sony BA-4D chassis RGB mod mux diagram

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.


  • 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.

  • R087 (680Ω)
  • R088 (680Ω)
  • R089 (680Ω)

STEP 2: 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 Brown wire here is used for blanking

KV-20S42 - RGB/Blanking wiring BA-4D chassis - Full RGB mod

KV-27S42 - RGB/Blanking wiring BA-4D chassis - KV-27S42 RGB mod

STEP 3: Connect Sync and Audio

Drilled some holes on the board for safe wire routing


  • Purple and black wires are for ground
  • Grey wire is for right audio
  • White wire is for left audio
  • Orange wire is ground, but you can clip it off
  • Yellow wire is for sync


Full mod (pic taken from Sony KV-20S90) BA-4D chassis - Full RGB mod

STEP 4: Build your mux board

Below 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 precalculated resistor values.

Buy your RGB mux board

TV ModelKV-20S40KV-20S90KV-20S42KV-27S42
CRT inline resistors5.6kΩ5.6kΩ5.6kΩ5.6kΩ
Audio LR (R7, R8)1kΩ1kΩ1kΩ1kΩ
RGB termination (R1, R2, R3)75Ω75Ω75Ω75Ω
RGB inline resistors (R4, R5, R6)1kΩ1kΩ1kΩ1kΩ
Diode (R9)1N41481N41481N41481N4148
Blanking Resistor (R11)1kΩ1kΩ1kΩ1kΩ
Add diodes to RGB linesYesYesYesYes



STEP 5: 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-20S42 img

Sony KV-20S90 img

Sony KV-27S42 img

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-20S42)

OSD overlay img

SNES - Metroid img

SNES - Super Mario World img

SNES - Contra img

NES - Adventure Island img

NES - Adventure Island closeup img

PS1 - Boot img

SNES Megaman X closeup img

Contra 3 closeup img

XBOX - UnleashX img

Games (KV-20S90)

Super Mario Kart img

Demon's Crest img

Zombies Ate My Neighbors img

Games (KV-27S42)





Grid - KV-20S90 img

Grid - KV-20S42 img

Grid - KV-27S42 img

Monoscope - KV-20S42 img

Monoscope - KV-27S42 img

SMPTE - KV-20S42 img

SMPTE - KV-20S42 (angle shot) img

SMPTE - KV-27S42 (angle shot) img

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