Sanyo AVM-20F5

# Sanyo AVM-20F5 CRT RGB mod

Is it possible to restore a CRT that went through a poor RGB mod? Let's find out. This tutorial covers the RGB mod for Sanyo AVM-20F5 (Flat 20", Sanyo CRT). These instructions should also work for the below CRTs.

The Sanyo AVM-20F5 is a 20" CRT television released around 2003, often used for retro gaming due to its flat screen, decent image quality, and inclusion of S-Video.

This set is RGB moddable.

View full CRT details and more mod examples →open in new window

Given that this CRT TV solely features one composite input at the front, two composite inputs, one s-video input, and an RF input at the back, it's certainly worthwhile to modify it for RGB input. Although a few adjustments are required, the modification process employs the standard mux mod.

# Backstory of the Sanyo CRT

Someone who purchased two RGB modded CRT tvs from me wanted their Sanyo CRT tv looked at. Upon initial inspection there was a heavy red tint. When we tried to get into the service menu, suddenly the CRT stopped working. It went into HV protection mode. Tube and the chassis were in great condition. This Sanyo CRT tv had undergone prior modifications by an individual, but the RGB mod was executed inaccurately. It was a bit challenging to take the back cover off, since everything was glued in place with no easy way to disconnect. Upon further inspection the problem was found to be poor RGB modding, incorrect resistor values and shorting of some pins. While the simplicity of just soldering the resistors directly to the SCART connector can be admired, sometimes it can cause more headache than what it's worth. I highly recommend you order the PCB with quick disconnect, so that you can easily service the CRT when needed.

# Contributors

Thank you to everyone who contributed to this guide:

• Suntharopen in new window — contributor, RGB mod and pictures

# CRT safety

READ THIS BEFORE CONTINUING

# Plan of attack

READ THIS TO PREPARE

# Manuals and Datasheets

• Toshiba TB1231CN Datasheet (Jungle)open in new window

# Calculating the RGB external resistor value

Love it when we can put theories to use! Formula from our theory page!

We find out using ohms law, this CRT is using ~0.7Vp-p. How?

Vp-p = 5V x (680/(4700+680)) = 5V x 0.1264 = 0.63V

RGB external resistor value
= (0.7 x (4700 + 75) - (75 x 5)) / (5 - 0.7)
= (0.7 x 4775 - 375) / 4.3
= 2967 / 4.3
= 690Ω

680Ω resistors should do the job. One thing to keep in mind is that the external resistor value calculated is typically very close to the resistor value removed.

# Specs

• Manufactured: USA ()
• Tube: LG A51QDJ279X
• Jungle Chip: Toshiba TB1231CN
• OSD Chip: KEC KMPA8701CMN-3B14
• Screen Size: 20"

# RGB mux 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 board 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.

• R007 (680Ω)
• R008 (680Ω)
• R009 (680Ω)

# STEP 2: Blanking diode

To prevent current from flowing back into the OSD and causing interferences in RGB mods, it's necessary to include a diode in the blanking line. The absence of this diode is the main cause of such issues.

Replace jumper J035 with a diode 1N4148. Pay attention to the direction of the diode.

# STEP 3: Connect RGB, Blanking

Refer to the picture below to connect the RGB and blanking wires. Be sure to solder them to the leg of the resistor that is facing away from the OSD chip.

# STEP 4: Sync and Audio

Sync and Audio can be connected to the Video input.

# STEP 5: Build your mux board

This 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 mux calculatoropen in new window to play with your own values.

Compatible mux boards:

• RGB MUX BOARD KIT 1.4Copen in new window
• RGB MUX BOARD KIT 1.4Bopen in new window

Buy your RGB mux board kit

To add a blanking diode, replace J035. Direction of the diode matters.

Although the calculations were helpful, a dedicated tuner board was utilized to identify the optimal combination of RGB inline and termination resistance required to achieve the ideal color balance. After testing, it was discovered that a 220Ω termination provided the finest RGB image.

# STEP 6: 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?

OSD overlay on top of PS1 boot logo showing the mux mod is working well.

# Remote Control for this TV

Despite not having the remote control for this CRT, I was able to use a universal Sony RM-AV3000 remote control with the code 8025 successfully.

# Pictures

# Reference Photos

See more photos and contributions →open in new window

# Games

NES - Adventure Island

NES - Barbie

Sega Genesis - Sonic

SNES - Megaman X

SNES - Yoshi's Island

SNES - Yoshi's Island (closeup)

SNES - Metroid (closeup)

PS1 game booting

PS1 Sony logo

# Patterns

Pattern - Grid

Pattern - SMPTE

# Chassis, Tube and Casing

Tube label

TV back open

TV neck yoke

TV front panel