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JVC AV-27230

SuntharAbout 3 minCRT RGB mod

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.

CRT safety


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.


Service manuals


  • 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



PCB diagram img

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.

  • W177
  • W178
  • W026
  • W214

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.

TV Model20D20227230
RGB/OSD inline resistor value4.7kΩ4.7kΩ
Removed RGB/OSD resistor value1.5kΩ1.5kΩ
In line diode methodYesYes
TV Model20D20227230
Audio LR (R7, R8)1kΩ1kΩ
RGB termination (R1, R2, R3)220Ω220Ω
RGB inline resistors (R4, R5, R6)1kΩ1kΩ
0.1uF caps replacedNoNo
Diode (R9)1N41481N4148
Blanking Ground Resistor (R10)?4.7kΩ
Blanking Resistor (R11)1kΩ1kΩ

This mod uses the RGB mini mux board (Rev C)



Buy your RGB mux board

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.

How to create and mount a SCART female plug?

Remote control and service menu

  • Press the SLEEP TIMER key and set the SLEEP TIMER for 0 MIN
  • While the SLEEP TIMER is displaying on the CRT, do the below
  • Immediately press the DISPLAY key and the VIDEO STATUS key of the remote control unit at the same time.
  • Then enter the SERVICE MENU screen shown in figure.


OSD mux overlay



NES - Adventure Island img

SNES - Super Metroid img

SNES - Super Metroid closeup img

SNES - Yoshi's Island img

SNES - Yoshi's Island closeup img

SEGA Genesis - Sonic closeup img

PS2 - Tombraider closeup img

SNES - Contra 3 closeup img


Monoscope img

RGB colors img


240p Grid img


Neck board img

Tube img

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