Sony KV (BA-5)
Sony BA-5 chassis CRT RGB mod
Below mod was performed on KV-20FV12. There are some special instructions for KV-20FS12, since it doesn't have a luma input you can tap into for reduced horizontal shift.
This tutorial should also cover the RGB mod for the below models with the BA-5 chassis. However, there might be slight differences.
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: October 2001, Mexico
- NTSC, 60 Hz
- Chassis: BA-5
- Jungle Chip: CXA2131CS
- OSD Chip: M37273MF
If you are building your own circuit, this diagram should help
Please note there is a second RGB input available in CXA2131CS. However, it is disabled in software. You can activate it by using I2C as documneted here. However, it is more effort than just doing a mux mod.
Calculating the RGB external resistor value
Formula from our theory page!
RGB external resistor value = 0.7 x (6800 + 75) - (75 x 5) / (5 - 0.7) = (4812 - 375) / 4.3 = 1030 ohm
~ 1 Kohm resistors should do the job.
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
Remove the following components. RGB resistors to the ground. Measure twice and mark before you remove.
- R1084 (680Ω)
- R1085 (680Ω)
- R1086 (680Ω)
Note: there can be slight differences in the board layout. I have seen slightly different MB board layout, even within the same 20FV12 CRTs.
STEP 2: Connect RGBs, Blanking and Audio
See picture above to see where blanking should be connected.
Let's remove the jumpers JW1335, JW1336, JW1337 and replace with 3 1N4148 diodes. Pay attention to the direction of the diodes. 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.
Twist the orange and yellow wires. Sync wire (yellow) should be connected directly to the s-video Y pin. Ground wire (orange) should be connected to the ground. Audio wiring can go below the board. Connect audio left (white) and audio right (grey) as seen in the pics below.
Ground both common ground (black) and audio ground (purple) wires.
STEP 2: Special instructions for KV-20FS12
Since there is no s-video you can tap into, try feeding sync to the negative leg of C1385 capacitor. That is the COMB Y input.
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.
|Audio LR (R7, R8)||1kΩ|
|RGB termination (R1, R2, R3)||75Ω|
|RGB inline resistors (R4, R5, R6)||1kΩ|
|Blanking Resistor (R11)||2.2kΩ|
You have to be strategic about the board placement. Sony KV-20FV12 has tight spacing with flyback and the audio board on the way.
It is recommended to use the Rev C mini board for this CRT with the straight SCART connector. Rev B board can be used, if the spacing is carefully planned.
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.
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
Mux and OSD
NES - Adventure Island
SEGA Genesis - Sonic
SNES - Contra
SNES - Alien
XBOX - UnleashX
PS1 - Boot
SMPTE - Colors
Inside of the CRT
Gut of the CRT (comes off completely). Main chassis, MB board, Neck board
Tube and speakers