Apex AT1302 CRT RGB mod
This tutorial covers the RGB mod for Apex AT1302. This mod was performed by Enrique Leon.
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
- Manufactured: Made in China
- NTSC, 60 Hz, 70W
- Chassis: CN-12C
- Tube: 37SX110Y22-DC15
- Jungle Chip: LA76814K
- OSD Chip: CHT0407
Get hold of the schematics for your TV. Understand where the RGB and Fast Blanking signals go from OSD to the Jungle (Chroma) chip.
R739 is the blanking in-line resistor. In the schematics it shows as it is 3.3kohms. Blanking ground resistor is also 3.3kohms. This says the blanking voltage is at 2.5V.
Performing the mod
STEP 1: Remove the following components
Remove the RGB resistors to ground
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.
|RGB inline resistros (R736, R737, R738) schematics||4.7kΩ|
|RGB inline resistros (R736, R737, R738) measured||3.3kΩ|
|Blanking inline resistor (R739)||3.3kΩ|
|Blanking ground resistor (R749)||3.3kΩ|
|RGB ground resistor (R746, R747, R748)||680Ω|
|RGB inline caps (C201, C203, C205)||0.01uF|
|Mux board audio LR (R7, R8)||1kΩ|
|Mux board RGB termination (R1, R2, R3)||220Ω|
|Mux board RGB inline resistors (R4, R5, R6)||680Ω|
|Mux board blanking diode (R9)||1N4148|
|Mux board blanking Resistor (R11)||3.3kΩ|
Please note 220Ω resistor was used for termination to balance contrast and brightness.
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?
Enrique's initial RGB modification was a success. By using a template, drill, and file, it is possible to create a more precise and tidy SCART cutout.