JVC AV-27230

SuntharAbout 3 min

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.

JVC AV-20D202

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

Service manuals

Specs

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

Schematics

PCB diagram

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 Model	20D202	27230
RGB/OSD inline resistor value	4.7kΩ	4.7kΩ
Removed RGB/OSD resistor value	1.5kΩ	1.5kΩ
In line diode method	Yes	Yes

TV Model	20D202	27230
Audio LR (R7, R8)	1kΩ	1kΩ
RGB termination (R1, R2, R3)	220Ω	220Ω
RGB inline resistors (R4, R5, R6)	1kΩ	1kΩ
0.1uF caps replaced	No	No
Diode (R9)	1N4148	1N4148
Blanking Ground Resistor (R10)	?	4.7kΩ
Blanking Resistor (R11)	1kΩ	1kΩ

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?

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.