# JVC AV-36850 CRT RGB mod

I did not mod this CRT. However, important lesson was learned from modding this CRT.

From deezdrama on reddit (opens new window):

This crt originally had composite and s-video only, its from 97 right before the D series .... The TA1242N jungle chip used on these CRTs were kind of a mystery. The chips data sheet is in Japanese and it was assumed from it that the jungle needed 0.5Vp-p rgb signals. Mark on shmups held my hand again through this one. We attenuated the signal to 0.5Vp-p and it was super dim. No amount of RGB levels or cutoff adjustment helped.

I was bummed out and thought I fried something when I turned the G2 (flyback brightness/screen) up too high to try and brighten the image.

Mark said he heard these chips needed 1Vp-p but it was basically unknown

Due to how dim 0.5Vp-p was I skipped 0.7Vp-p which is the SCART standard and went for 1Vp-p by removing attenuation resistors, using 180 ohm termination, and swapped mux resistors to 510 ohm. It came out perfect!

A tiny tweak to the G2 was all that was needed.

I own a dozen or so pvm/pro/ broadcast monitors and this tube here is now one of my favorite tubes! It was a pain to pick up, haul upstairs, recap, clean, and mod twice but glad I stuck with it! It was definitely worth the troubles!!!

# CRT Safety

DANGER

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

Note: the service manual for this TV doesn't seem to have the schematics.

# RGB Mux Schematics

Thanks to MarkOZLAD/deezdrama

RGB img

Blanking img

# Mod details

Thanks to MarkOZLAD/deezdrama

  1. Remove SMD resistors R717, R719, R721 (factory OSD "grounding" resistors)
  2. For blanking we want to go from a 5V source into a switch then into a 1.8K resistor and then onto jumper W019
  3. For each of the RGB lines we want to bring in the external RGB, we want 180 ohm to ground. Then for each run a line from between these two resistors onto the RGB jumpers into a 510 ohm resistor then onto their respective jumpers.
  4. Replace caps C801, 802 and 803 with 0.1uF (104) ceramic caps
  5. Sync into factory AV port (composite or svideo luma, even component Y)

This is the way.

YouTube (opens new window)

# Pictures

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