# Sony BA-4D Chassis CRT RGB mod

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

  • KV-27S42
  • KV-27S46
  • KV-27S66
  • KV-20S90

# 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


# Theory

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

# Specs

# Sony KV-20S90

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

# Schematics

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 and other BA-4D chassis.

Sony BA-5 chassis RGB mod mux diagram

# Calculating the RGB external resistor value

Formula from our theory page!


Calcualted 910Ω for 0.7Vp-p

# 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.

# STEP 1: Remove the following components

BA-4D chassis - MB Board

Remove the following components. RGB resistors to the ground. Measure twice and mark before you remove.

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

# STEP 2: Connect RGBs, Blanking and Audio

See picture above to see where blanking should be connected.

Let's remove the jumpers and add 3 1N1418 diodes. Pay attention to the direction of the diode. There is a black bar indicating which way the current flows. This helps reduce feedback noise and voltage going back into the OSD.

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

BA-4D chassis - Full RGB mod

# STEP 3: 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 Model KV-20S90
Audio LR (R7, R8) Shorted
RGB termination (R1, R2, R3) 75Ω
RGB inline resistors (R4, R5, R6) 1kΩ
Diode (R9) 1N4148
Blanking Resistor (R11) 1kΩ

You have to be strategic about the board placement. Sony KV-20FV12 has tight spacing with flyback and the audio board on the way.

# STEP 4: 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?


# 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

Super Mario Kart img

Demon's Crest img

Zombies Ate My Neighbors img

# Patterns

Grid img