Sony KV (BA-5)

SuntharAbout 4 min

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.

KV-20FS12
KV-20FV12
KV-21FE12
KV-21FM12
KV-24FV12
KV-27FS13
KV-27FS17
KV-27FV17
KV-29FV17
KV-32FS13
KV-32FS17
KV-34FS17

You can also checkout the KV-24FV12 RGB mod performed by Davide here.

CRT safety

Caution

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.

READ THIS BEFORE CONTINUING

Plan of attack

READ THIS TO PREPARE

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.

READ THE RGB MODDING THEORY

Service manuals

Specs

Sony KV-20FV12

Manufactured: October 2001, Mexico
NTSC, 60 Hz
Chassis: BA-5
Tube:
Jungle Chip: CXA2131CS
OSD Chip: M37273MF

Schematics

Sony BA-5 chassis schematics

Mux diagram

If you are building your own circuit, this diagram should help

Sony BA-5 chassis RGB mod mux diagram

Please note there is a second RGB input available in CXA2131CS. However, it is disabled in softwareopen in new window. You can activate it by using I2C as documneted hereopen in new window. 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

BA5 chassis - MB Board

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.

Buy your RGB mux board

TV Model	KV-20FV12	KV-20FS12	KV-24FV12	KV-32FS13
Audio LR (R7, R8)	1kΩ	1kΩ	1kΩ	1kΩ
RGB termination (R1, R2, R3)	75Ω	75Ω	75Ω	75Ω
RGB inline resistors (R4, R5, R6)	1kΩ	1kΩ	1kΩ	1kΩ
Diode (R9)	1N4148	1N4148	1N4148	1N4148
Blanking Resistor (R11)	2.2kΩ	2.2kΩ	2.2kΩ	2.2kΩ
Add diodes to RGB lines on set	Yes	Yes	Yes	Yes
Add diodes to Blanking line on set	No	No	No	No
Follow special instructions for sync	No	Yes	No	No

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

Buy your RGB mux board

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.