JVC AV-27120

# JVC AV-27120 RGB mux mod

This mod was performed by Martin Seibert!

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In this tutorial, we will be discussing the RGB modification process for the JVC AV-27120 CRT. RGB mod for JVC AV-27220 is also very similar. This particular model boasts an exceptional tube with impressive geometry. 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

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

• JVC AV-27220 Service Manual
• TB1242N Datasheet

# Specs

• Manufactured: March 2000, Assembled in Mexico
• NTSC, 60 Hz, 113W
• Chassis: FV Chassis
• Tube: RCA Thomson A68ADT25X01
• Jungle Chip: TB1242N (0.7V p-p on EXT RGB input from datasheet)
• OSD Chip: M37272MA-313SP

Specs and tube are same as JVC-AV27230.

# Schematics

This mux diagram is for JVC AV-27230. While the Chroma IC is different, the resistor values and setup are the same. 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)

# STEP 2: Install diodes to reduce noise

Diodes were not installed on chassis for this mod. However, it is recommended to reduce noise. See JVC-AV27230.

# 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. Please remember, the below R, G, B, blanking solder locations for wiring would be different if you were to install diodes.

The sync was connected to the composite input that was already 75Ω terminated, 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.

Black wire is the common ground for both audio and video. Purple and orange wires are for auxillary purposes and can be grounded (suppose you want to add a switch based mod or you can also use them for S-Video mod).

# 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.

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.

# Pictures

# Games

# Patterns

SMPTE

240p Grid

# Set