RCA F20352SF

# RCA 20" F20352SF RGB mod

This turned out beautifully. This 20" set features an RCA tube that delivers a soft, arcade-like glow. The same mod should work for models using the CTC177 chassis or LA610 chroma ICs. Several mods shared on Shmups appear to have failed due to the unusual transistor amp present in the RGB path. Several also skipped the required diodes on the R, G, B, and blanking lines — these are essential for reducing noise. The models listed below can benefit from this tutorial, though minor variations may apply.

• RCA 27CR620
• Chassis CTC177AH

More pictures of the set and details here: RCA F20352SFopen in new window

# Table of Contents

# 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

# Specs

# RCA F20352SF

• Chassis: CTC176
• Chroma: LA7610
• OSD: ST15053-46B

# Service manuals

There may be minor variations in component numbering—for instance, C708 might also appear as C2708.

• RCA CTC176 Service Manual

# Schematics

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 RGB resistors that are connected to the ground.

• R317 (120Ω)
• R319 (120Ω)
• R321 (120Ω)

# STEP 2: Add inline diodes to reduce interference

This is an important step to replace the following jumpers with diodes.

• JW466
• JW465
• JW467
• JW436

Not doing this means, there will be interferene. Pay attention to the direction of the diode, which is represented by the black bar on the diode.

# STEP 3: Connect RGB and Blanking

Attach RGB wires and blanking on exactly where these resistors were removed.

# STEP 4: Permanently enable stereo (optional)

Stereo can be permanently enabled by removing the lip seen in the below picture. Alternatively, plugging anything into the red RCA port will also activate stereo.

# STEP 5: Connect Audio, Sync and Ground

Composite Sync, Audio and Ground wires should be connected.

# STEP 6: Build your mux board/circuit

Below 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.

Buy your RGB mux board

Buy your RGB mux board

Used the tuner to come up with the optimal values.

# Pictures