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Toshiba 20AF43+

SuntharAbout 3 minCRT RGB mod

Toshiba 20AF43+ CRT RGB mod

This tutorial covers the RGB mod for the below models.

  • Toshiba 20AF43
  • Toshiba 20AF44
  • Toshiba 20AF45
  • Toshiba 20AF46

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Please also see other Toshiba AF series mods, as the instructions are more or less the same.

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

Specs

20AF45

  • Chassis: M3S027
  • Manufactured: Thailand, August 2005
  • Power Consumption: 105W, 120V, 60Hz (NTSC)
  • Tube: Orion A51LYZ095X8

Service manuals

Schematics

Get hold of the schematics for your TV. Understand where the RGB and Fast Blanking signals go from OSD to the Jungle (Chroma) chip.

20AF43/20AF44

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20AF45/20AF46

The biggest difference between 20AF44 vs 20AF45 is there is no VM circuitry (the one that is used for edge enhancements). Therefore, D107, D108 and D110 are missing from this schematics.

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PCB

20AF43/20AF44/20AF45/20AF46

Points where the R, G, B and Blank wires should be connected are marked "X". Pink boxes show the resistors, diodes that needs to be removed.

Actual PCB might be slightly different for 20AF45 and 20AF46. However, the mod that needs to be applied is in similar location.

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Performing the mod

STEP 1: Remove the following components

20AF43/20AF44

Remove the RGB resistors to ground

  • R141
  • R142
  • R143

There were no coupling capacitors to ground that needed to be removed

Tips

Did not remove C131 or C135. Removing them can affect the background of the OSD.

VM can be disabled in two ways

Method 1: Unplug the VM cable on the neck board. img

Method 2: Remove diodes that enable VM from the RGB lines (not recommended)

  • D107
  • D108
  • D110

20AF45/20AF46

Remove the RGB resistors to ground

  • R141
  • R142
  • R143

There are no VM cables to unplug on the neck board. No VM diodes to remove on this board.

STEP 2: Connect RGBs, Blanking and Audio

20AF43/20AF44/20AF45/20AF46

Connect the RED, GREEN, BLUE, BLANKING wires img

Connect the SIGNAL, AUDIO RIGHT, AUDIO LEFT, GROUND wires img

STEP 3: Build your mux circuit

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

Depending on the RGB/OSD stock resistors your CRT has, use the below inline resistors.

TV Model20AF4220AF4x20AF4x20AF4x
RGB/OSD stock resistors4.7kΩ3.3kΩ3.9kΩ6.8kΩ
Audio LR (R7, R8)1kΩ1kΩ1kΩ1kΩ
RGB termination (R1, R2, R3)75Ω75Ω75Ω75Ω
RGB inline resistors (R4, R5, R6)680Ω470Ω560Ω1kΩ
Diode (R9)1N41481N41481N41481N4148
Blanking Resistor (R11)shortedshortedshortedshorted

Toshiba 20AF45 RGB mux adapter img

Toshiba 20AF44 RGB mux adapter img

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?

Alternate method to reduce ringing noise

If you don't have diodes on the OSD RGB lines connecting to the chroma chip, the RGB signals that comes from the console can hit the OSD chip and reflect back, causing a minor interference. While not very noticeable, if you are keen on keeping all forms of noise away from your mod, you should follow the below directions.

Step #1: Remove the ground resistors.

  • R141
  • R142
  • R143

Also remove the 0.1uF SMD caps that are inline

  • C136
  • C137
  • C138

Step #2: Introduce diodes and 0.1uF caps

Mux Diagramimg

Connect RGB, Blanking wires

Remove the jumper wires that feeds the R, G, B lines from OSD to Chroma. Forgot to take a picture of this, but this is an important step to perform.

Removed caps are bridged. Caps and didoes added. Pay attention to the direction. img

Blanking wires and RGB wires attached. img

Connect Audio, Sync and Ground wiresimg

Step #3 and #4

These are the same as above. Only difference here is the RGB inline resistance value to use will be 1.2kΩ instead of 1kΩ. This is to compensate for the addition of the diodes.

Pictures (20AF44)

Finished mod

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Yes, screws are missing. They were put in later!

Test patterns

Not the best image quality. But, looks pretty decent for a flat CRT TV.

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Games

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Pictures (20AF45)

Mux board and port

SCART port img

Cable connected img

OSD Mux overlay

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Games

SNES - Super Mario World img

SNES - Metroid img

NES - Adventure Island img

XBOX - UnleashX img

Sega Genesis - Sonic img

Patterns

Convergence img

Monoscope img

Tube and Board

Tube img

Back label img

Back open img

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