JVC AV-27230 RGB mux mod
In this tutorial, we will be discussing the RGB modification process for the JVC AV-27230 CRT. This particular model boasts an exceptional tube with impressive geometry, and unlike the highly coveted earlier JVC D-Series (e.g. AV-27D201), there were no distracting funhouse scrolling problems observed. Therefore, if you own a JVC curved set that can be RGB modified (some can't be modified), I strongly endorse trying out this modification.
Looking through the service manuals these instructions should also work for other JVC models with Toshiba chroma ICs.
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: December 2001, Assembled in Mexico
- NTSC, 60 Hz, 113W
- Serial Number: 17616653 R
- Chassis: A67 FD Chassis
- Tube: RCA Thomson A68ADT25X01
- Jungle Chip: TB1253AN (0.7V p-p on EXT RGB input from datasheet)
- OSD Chip: M37272MA-314SP
Prepare the mux diagram. If you are building your own circuit, this diagram should help
Performing the mod
Now that you roughly know what needs to be done, prepare for the mod. Place the main chassis 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.
- R738 (1.5 kΩ)
- R740 (1.5 kΩ)
- R742 (1.5 kΩ)
Note: It was strange that the chassis did not include a ground resistor for blanking. This ground resistor is shown in the schematics however. To address this issue, a 4.7 kΩ (R10) ground resistor was added to the mux board.
STEP 2: Install diodes to reduce noise
Remove the following jumpers and replace them with 4 diodes.
Pay attention to the direction of the diodes. Also, install the diodes on the component side of the chassis, as seen in the picture below.
STEP 3: Connect RGBs, Blanking and Audio
The picture presented below depicts the appropriate placement for soldering the R, G, B, and blanking wires onto the solder side of the chassis. It is crucial to solder them on the correct side of the diode installation location, as illustrated in the image.
The sync was linked to the component luma pin, while the audio was connected to the corresponding left and right audio inputs. It's important to remember that in order for the stereo sound to function properly, a dummy RCA must be inserted into the right channel's red audio RCA port.
The ground wires consist of the purple and black wires, with an additional redundant ground wire in orange. The latter was deliberately cut off and insulated, taking care to avoid any short circuits on the main chassis.
STEP 4: Build your mux board
Below mod uses the RGB mux board. I strongly suggest adopting this board and its well-established technique in your RGB mod, especially since the files are accessible for self-manufacturing. Please also checkout the precalculated resistor values.
|RGB/OSD inline resistor value
|Removed RGB/OSD resistor value
|In line diode method
|Audio LR (R7, R8)
|RGB termination (R1, R2, R3)
|RGB inline resistors (R4, R5, R6)
|0.1uF caps replaced
|Blanking Ground Resistor (R10)
|Blanking Resistor (R11)
This mod uses the RGB mini mux board (Rev C)
STEP 5: Attach the female SCART connector to TV
Creating a SCART cutout and mounting it is an art. I have a dedicated section for it.
Remote control and service menu
- Press the
SLEEP TIMERkey and set the
- While the
SLEEP TIMERis displaying on the CRT, do the below
- Immediately press the
DISPLAYkey and the
VIDEO STATUSkey of the remote control unit at the same time.
- Then enter the
SERVICE MENUscreen shown in figure.
OSD mux overlay
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SNES - Yoshi's Island closeup
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