Sony KV (BA-4) 27V40
Sony BA-4 chassis RGB and YPbPr mod
Bring your Sony CRT to life with vibrant RGB colors!
BA-4D has a similar chassis and the tutorial for it can be found here.
If you're looking to get the most out of your Sony KV-27V40 Trinitron, you may want to consider modding it for RGB and component output. This guide will show you how to do just that.
Instructions below should also apply to these models:
- Sony KV-27V40
- Sony KV-27V45
- Sony KV-27V65
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.
- Manufactured: February 1999, Mexico
- NTSC, 60 Hz, 140W Max
- Chassis: BA-4
- Jungle Chip: CXA2061S
- OSD Chip: M37273MF
If you are building your own circuit, this diagram should help. The diagram is for KV-27V40, it will also work for any other BA-4 chassis.
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.
- Degauss wire
- Power wire
- Ground wire attached to the neck board
- Yoke deflection coil wire
- Anode wire (this is the one with the rubber cap)
- 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.
- 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
- 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 3: RGB inline diodes
To reduce interference, it is recommended to add these inline diodes. Heat shrink was used in the middle one to avoid shorts.
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
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
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.
|Audio LR (R7, R8)||1kΩ||1kΩ||1kΩ|
|RGB termination (R1, R2, R3)||75Ω||75Ω||75Ω|
|RGB inline resistors (R4, R5, R6)||1kΩ||1kΩ||1kΩ|
|Blanking Resistor (R11)||1kΩ||1kΩ||1kΩ|
|Add diodes to RGB lines||Yes||Yes||Yes|
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.
Holes for an unused AV jack were used for YPbPr jacks for a factory look.
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
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
Street Fighter II
Street Fighter II
Street Fighter II
Street Fighter II