New to CRT Modding

[steelinthefield]

I've been poking around on there off and on for the last year or so. Been trying to glean everything I can to understand how to go about RGB modding a CRT or adding s-video if the set can't be RGB modded. I'm familiar with the CRT database and how it has good info for specific sets but mine is not listed as being confirmed RGB moddable or being able to have s-video added to it.

I've got a Sony KV1380R and I'd like some help to figure out if either of these can be added to it. https://archive.org/details/sony-kv-1380-r-sm

I found an old thread where someone was looking into doing mods to this set but the person was doing it for someone else and they changed their mind and didn't want to have it modded. If it's at all helpful I will viewtopic.php?t=65583&start=90

I'm having trouble deciphering the schematics from the service manual. I often see people mention looking for the Jungle chip and looking for the Y/C section. I think i've found it but it's hard to really know what to do with it. Can anyone help point me in the right direction with how to go through the schematic to find the various parts i either need to inject chroma or luma into etc and/or what jumpers to cut if need be? This set does have OSD so perhaps muxing is possible?

thank you!

[KPackratt2k]

I've managed to add S-Video to a Sony KV-1380R TV a few months ago. There are no RGB inputs on the jungle chip, so RGB modding it is out of the question without resorting to a neckboard amp, which is difficult.

The video processing circuitry is on the hot side of the chassis and the AV inputs are isolated from it using optocouplers, so you should use this optocoupler PCB to isolate the Chroma input:
https://oshpark.com/shared_projects/KZcv086o

R5 should be a 3.3 ohm resistor to match the value of the stock resistor value for the video input circuit.

IC301 pin 39 is the Chroma input pin. Lift C323 and C319 out of its path and tie the two capacitor legs together. C317 and C318 should also be removed to take the 3.58MHz trap filter out of circuit.

The optocoupler should be wired as follows:
Cold power and ground (the 2-pin JST on the top-left of the isolator board):
VCC (Cold Side) <- Cold 12V (R412 leg away from pin 2 of IC401)
GND (Cold Side) <- Video input ground - can solder the wire to the JST connector where the AV inputs connect to the A board.

S-Video Chroma input (the 2-pin JST on the bottom-left of the isolator board):
C_IN <- S-Video Chroma (Pin 4)
GND -> Ground point for shielded wire, the other end should be connected to the ground pins of the S-Video jack (the shield and pins 1-2.)

Hot power and ground (the 3-pin JST on the top-right of the isolator board):
VCC (Hot side) <- Hot 12V (IC401 pin 8)
Middle pin is not connected to anything.
GND (Hot side) <- Hot ground (IC401 pin 5)

Chroma I/O from the TV chassis (the 2-pin JST near the 4-pin JST on the bottom-right of the isolator board):
YCJ_IN <- IC301 pin 39, can inject to the pad where C323 was lifted out of circuit.
TV_C <- C323 and the non-grounded end of C319 tied together.

Chroma I/O to the first pole of a 3PDT switch (the 4-pin JST on the bottom-right of the isolator board):
C_OUT -> Pin 1 of the switch
YCJ_IN -> Pin 2 of the switch
TV_C -> Pin 3 of the switch
GND -> A grounding point for shielded wire, provided for convenience.

Shielded wire should be used for the Chroma connections, as they're sensitive to interference as I've discovered while prototyping the mod.

Take the two capacitors you've removed from C318 and C317, solder them to pins 4 and 7 of the 3PDT switch, tie the other ends together and run it to a wire leading to either (C317/C318) capacitor pad leading to T301. Run pins 5 and 8 of the switch to the capacitor pads that lead to R321.

You can mount the optocoupler board on top of the RF tuner module using 3M VHB double sided tape. I recommend placing two layers of kapton tape on the bottom of the board before putting the double sided tape on it.

S-Video Luma (Pin 3) can be connected to the Composite video input.

It is also recommended to replace R317 with a 47K ohm resistor to reduce sharpness ringing on the image.

I'll look for the photo of the jack panel later to post for a suggestion on where to place the S-Video jack and the switch, along with DigiKey links to the ones I used. Hopefully I've provided enough details to help you work on this mod.

[steelinthefield]

Wow. Thank you for all the time you spent writing this all up. Honestly it's a bit hard for me to follow all of this. Good to know s-video is possible.

As far as the optocoupler goes. This is my first time hearing about this pcb. It sounds like I order the one you linked along with all the components for it. Then I solder the various components onto it/the tv's board based on your instructions and it gets attached to one of the tv's boards.

I think your description of what to solder where and how to disconnect and connect stuff is still a little bit confusing to me. When i lift the C323 and C319 out of its path and tie the two capacitor legs together, i dont really understand what that means. Obviously I desolder them but i'm confused as to if I remove them completely? But then i'm supposed to tie the legs together?

I think I'm struggling to also know where on the boards all of these things are and what they actually are. Is there a guide you can point me to understand what cold power is? or other things that appear like common CRT knowledge but I'm just getting lost in.

Sorry!

[KPackratt2k]

I think your description of what to solder where and how to disconnect and connect stuff is still a little bit confusing to me. When i lift the C323 and C319 out of its path and tie the two capacitor legs together, i dont really understand what that means. Obviously I desolder them but i'm confused as to if I remove them completely? But then i'm supposed to tie the legs together?

I think I'm struggling to also know where on the boards all of these things are and what they actually are. Is there a guide you can point me to understand what cold power is? or other things that appear like common CRT knowledge but I'm just getting lost in.

Sorry!

On the factory schematic, C323 is connected to the Chroma input (pin 39) of the jungle chip with C319 placed between it and ground. You lift these capacitors from the ends connected to the jungle chip, tie the lifted ends together out of the circuit, solder a wire to those tied capacitor legs to run to the TV_C pin of the 2-pin connector on the optocoupler board, then solder another wire through the TV chassis PCB via where C323 was originally connected to and run it to the YCJ_IN pin of 2-pin connector on the optocoupler board.

In other words, you don't remove those two capacitors entirely. You just disconnect them from the jungle chip, run the lifted ends of them to TV_C, then run the jungle chip's Chroma input pin to YCJ_IN.

A hot chassis TV has its ground connected to the Neutral blade of the AC power cable (sometimes directly, but in most cases there will be resistance between the two), which can cause an electric shock if you touch a ground point on the TV chassis (the tuner shield, for example) while it's plugged in. To avoid the danger of electrocution and/or equipment damage when connecting a device to the inputs, they are isolated from the hot chassis through either a network of capacitors in the case of the RF input or a set of optocouplers in the case of the AV inputs. The optocouplers require power and ground connections on both the cold and hot sides of the ICs, so there's a small isolation transformer inside the TV to provide the power and ground for the cold side of the optocouplers. The hot and cold power supplies are separated from each other and therefore have no continuity between the two sides.

On the TV chassis, there are component references (for example: a C101 label near the corresponding capacitor) near the actual components to tell you what goes where. The service manual has a list of components on the PCB to help determine their values. You can use a multimeter to measure the components as you spot them on the board and compare the measurements against the values specified on the component list on the service manual.