Toshiba 20AF43+ CRT RGB mod
This tutorial covers the RGB mod for the below models.
- Toshiba 20AF43
- Toshiba 20AF44
- Toshiba 20AF45
- Toshiba 20AF46
Please also see other Toshiba AF series mods, as the instructions are more or less the same.
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.
- Chassis: M3S027
- Manufactured: Thailand, August 2005
- Power Consumption: 105W, 120V, 60Hz (NTSC)
- Tube: Orion A51LYZ095X8
Get hold of the schematics for your TV. Understand where the RGB and Fast Blanking signals go from OSD to the Jungle (Chroma) chip.
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.
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.
Performing the mod
STEP 1: Remove the following components
Remove the RGB resistors to ground
There were no coupling capacitors to ground that needed to be removed
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.
Method 2: Remove diodes that enable VM from the RGB lines (not recommended)
Remove the RGB resistors to ground
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
Connect the RED, GREEN, BLUE, BLANKING wires
Connect the SIGNAL, AUDIO RIGHT, AUDIO LEFT, GROUND wires
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.
Depending on the RGB/OSD stock resistors your CRT has, use the below inline resistors.
|RGB/OSD stock resistors||3.3kΩ||3.9kΩ||6.8kΩ|
|Audio LR (R7, R8)||1kΩ||1kΩ||1kΩ|
|RGB termination (R1, R2, R3)||75Ω||75Ω||75Ω|
|RGB inline resistors (R4, R5, R6)||470Ω||560Ω||1kΩ|
|Blanking Resistor (R11)||shorted||shorted||shorted|
Toshiba 20AF45 RGB mux adapter
Toshiba 20AF44 RGB mux adapter
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.
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.
Also remove the 0.1uF SMD caps that are inline
Step #2: Introduce diodes and 0.1uF caps
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.
Blanking wires and RGB wires attached.
Connect Audio, Sync and Ground wires
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.
Yes, screws are missing. They were put in later!
Not the best image quality. But, looks pretty decent for a flat CRT TV.
Mux board and port
OSD Mux overlay
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