How to RGB mod a TV that only have RF IN?

[spikespiegel]

Working with a Chassis U6B 14'' Toshiba CRT consumer TV, the TV has no A/V (composite video) IN, but I've noticed that it might be possible to RGB mod it using the Jungle chip.
This is the schematic: https://www.electronica-pt.com/esquema/ ... info/7141/
Sorry about the language not being English, the only schematic I could find was that one, but I believe no one will have a problem reading it.

There's RGB written in two parts, one is the microcontroller, the other one I don't know what it is, the jungle chip? But it's written "RGB Clamp", please tell me those are analog RGB INs, cause it makes no sense for them to be digital, due to this TV being pretty old, since it only have a RF In, but I've noticed that it has a circuit for A/V and maybe S-video, it's just that there's nothing soldered there, The A/V is also drawned on the case.

If that's possible to RGB mod it, I presume first I'd have to look for the sync inside the A/V area (page 1, where it's written Placa A/V), is it the TV IN or the AV IN on ICV01 LVA508S? There's also e S-IN, is it S-video? well, I need to find the Sync IN...

Anyone have any experience with RGB modding CRTs that only have RF IN?

[KPackratt2k]

Before you proceed to mod this TV, make sure it's not a hot chassis. Many TVs without AV inputs lack an isolation transformer on the power supply circuit, with only the Coaxial jack isolated by its own isolation transformer placed between the tuner and the jack.

The easiest way to tell is if there's a transformer between the tuner and the jack. You should also check for continuity between the jack and the tuner shield. If you don't get any continuity, then the jack is isolated from the chassis. Otherwise, you should be good to go.

The AV inputs are most likely disabled via firmware as is the case on TVs that have unpopulated provisions for them. Check the service menu to see if there are any option bits you can change. If not, then you'll have to do one of the following:

A) Isolate the AV circuit from the tuner to the jungle chip and inject your sync and audio into the jungle's inputs.
B) Snoop the I2C bus and change the appropriate registers. This will require a datasheet for the jungle chip so you can see what the registers are and which ones to change.
C) Find a firmware dump from another set with the same chassis, but with AV inputs.

RGB Clamp should be a sign that it's Analog RGB, as Analog RGB is clamped whereas Digital is not.

[spikespiegel]

Before you proceed to mod this TV, make sure it's not a hot chassis. Many TVs without AV inputs lack an isolation transformer on the power supply circuit, with only the Coaxial jack isolated by its own isolation transformer placed between the tuner and the jack.

The easiest way to tell is if there's a transformer between the tuner and the jack. You should also check for continuity between the jack and the tuner shield. If you don't get any continuity, then the jack is isolated from the chassis. Otherwise, you should be good to go.

The AV inputs are most likely disabled via firmware as is the case on TVs that have unpopulated provisions for them. Check the service menu to see if there are any option bits you can change. If not, then you'll have to do one of the following:

A) Isolate the AV circuit from the tuner to the jungle chip and inject your sync and audio into the jungle's inputs.
B) Snoop the I2C bus and change the appropriate registers. This will require a datasheet for the jungle chip so you can see what the registers are and which ones to change.
C) Find a firmware dump from another set with the same chassis, but with AV inputs.

RGB Clamp should be a sign that it's Analog RGB, as Analog RGB is clamped whereas Digital is not.

I'm a bit lost here... I've never RGB modded a RF CRT before, only TVs with composite video and component video.
Do you mind showing me sample pictures of what you've mentioned or can I upload the schematic as jpg pictures here and you draw a red circle around the parts that you've cited that needs to be isolated?

"A) Isolate the AV circuit from the tuner"
By tuner you mean the whole RF component, covered with a metal case, with a circuit inside?

"to the jungle chip and inject your sync and audio into the jungle's inputs."
You mean that I should cut out the connection (traces) that the RF and Jungle chip have?

[spikespiegel]

Before you proceed to mod this TV, make sure it's not a hot chassis. Many TVs without AV inputs lack an isolation transformer on the power supply circuit, with only the Coaxial jack isolated by its own isolation transformer placed between the tuner and the jack.

The easiest way to tell is if there's a transformer between the tuner and the jack. You should also check for continuity between the jack and the tuner shield. If you don't get any continuity, then the jack is isolated from the chassis. Otherwise, you should be good to go.

The AV inputs are most likely disabled via firmware as is the case on TVs that have unpopulated provisions for them. Check the service menu to see if there are any option bits you can change. If not, then you'll have to do one of the following:

A) Isolate the AV circuit from the tuner to the jungle chip and inject your sync and audio into the jungle's inputs.
B) Snoop the I2C bus and change the appropriate registers. This will require a datasheet for the jungle chip so you can see what the registers are and which ones to change.
C) Find a firmware dump from another set with the same chassis, but with AV inputs.

RGB Clamp should be a sign that it's Analog RGB, as Analog RGB is clamped whereas Digital is not.

Does taking a shock from the GND count as a hot chassis? Cause I did. lol

[KPackratt2k]

Do you mind showing me sample pictures of what you've mentioned or can I upload the schematic as jpg pictures here and you draw a red circle around the parts that you've cited that needs to be isolated?

"A) Isolate the AV circuit from the tuner"
By tuner you mean the whole RF component, covered with a metal case, with a circuit inside?

"to the jungle chip and inject your sync and audio into the jungle's inputs."
You mean that I should cut out the connection (traces) that the RF and Jungle chip have?

Refer to the datasheet for the jungle chip to find the pins that the TV tuner is sending video and audio to (usually the video pin is labeled "TV In" and the audio pin is labeled "TV Audio In"), cut the connection from those pins to the tuner, and experiment with injecting Composite video and audio into those pins. You may need additional components to amplify the signal (for example: a transistor) depending on the voltage levels the jungle is expecting on those pins, so it would be a good idea to use a breadboard to test various methods of processing the signal.

You can provide the schematic in the form of an image for me to look at.

Does taking a shock from the GND count as a hot chassis? Cause I did. lol

Depends on the grounded part you've touched. Certain power regulators can be on the hot side of the chassis (even on isolated power supply designs), but if you've touched something that should be isolated on a TV chassis with an isolated power supply design (i.e. the RF tuner shield) and got shocked, then it's a hot chassis unfortunately. In which case you should either leave the set as it is or use an isolation transformer when connecting the set to power.

Isolating your input connections with optocouplers is possible, but I haven't done enough experimentation with that idea to determine the best approach to this.

[spikespiegel]

Do you mind showing me sample pictures of what you've mentioned or can I upload the schematic as jpg pictures here and you draw a red circle around the parts that you've cited that needs to be isolated?

"A) Isolate the AV circuit from the tuner"
By tuner you mean the whole RF component, covered with a metal case, with a circuit inside?

"to the jungle chip and inject your sync and audio into the jungle's inputs."
You mean that I should cut out the connection (traces) that the RF and Jungle chip have?

Refer to the datasheet for the jungle chip to find the pins that the TV tuner is sending video and audio to (usually the video pin is labeled "TV In" and the audio pin is labeled "TV Audio In"), cut the connection from those pins to the tuner, and experiment with injecting Composite video and audio into those pins. You may need additional components to amplify the signal (for example: a transistor) depending on the voltage levels the jungle is expecting on those pins, so it would be a good idea to use a breadboard to test various methods of processing the signal.

You can provide the schematic in the form of an image for me to look at.

Does taking a shock from the GND count as a hot chassis? Cause I did. lol

Depends on the grounded part you've touched. Certain power regulators can be on the hot side of the chassis (even on isolated power supply designs), but if you've touched something that should be isolated on a TV chassis with an isolated power supply design (i.e. the RF tuner shield) and got shocked, then it's a hot chassis unfortunately. In which case you should either leave the set as it is or use an isolation transformer when connecting the set to power.

Isolating your input connections with optocouplers is possible, but I haven't done enough experimentation with that idea to determine the best approach to this.

I was executing the normal procedure, screwdriver connected through a wire to the tube ground (that steel wire, I don't know how it's called in English) to discharge the tube when needed. I was sitting on the floor, with the TV on the floor, in home, testing the TV after fixing it, when I accidently touched the screwdriver and received a shock that felt like at least 80 volts AC. I wasn't supposed to take a shock from that part, right? I mean, I've touched it before, but I wasn't grounded, I wasn't sitting on the floor, neither I had my feet unprotected, and obviously didn't take a shock, so I presume if I touch the tuner when I'm grounded I'll take a shock too.

By the way, just found that my TV model (probably) uses the chassis UNIV5 as I noticed only today that the model is written on the board, it is a Toshiba TV1480E, but the other Schematic from a U6B Chassis has the very same components and connections, so I'm going to be posting both (and for me they're the same thing):

Chassis UNIV5:
Page 1


Page 2


Page 3


Page 4


Page 5


Page 6


Chassis U6B:

Page 1


Page 2


Page 3


Page 4

[KPackratt2k]

I took a look at the schematic you've posted and have determined that it's a hot chassis. There are optocouplers to isolate the AV inputs on the models that have them and the antenna input block has a set of three capacitors in parallel between the ground of the tuner and the shield on the input jack to isolate it.

In addition, the RGB Clamp/input pins are for either a clamping circuit or TTL OSD inputs according to the datasheet, so this jungle likely can't be modded for Analog RGB.

It should be possible to mod for Composite video and audio by simply copying the circuit from the models that have the inputs, provided you can still find all of the parts (or at least modern equivalents that match in specifications and pinouts of the originals). In this case, it's important to use optocouplers to isolate the signals.

[spikespiegel]

I took a look at the schematic you've posted and have determined that it's a hot chassis. There are optocouplers to isolate the AV inputs on the models that have them and the antenna input block has a set of three capacitors in parallel between the ground of the tuner and the shield on the input jack to isolate it.

In addition, the RGB Clamp/input pins are for either a clamping circuit or TTL OSD inputs according to the datasheet, so this jungle likely can't be modded for Analog RGB.

It should be possible to mod for Composite video and audio by simply copying the circuit from the models that have the inputs, provided you can still find all of the parts (or at least modern equivalents that match in specifications and pinouts of the originals). In this case, it's important to use optocouplers to isolate the signals.

Then I'll just finish fixing this TV and give it to someone else. Can you tell why this model after like 15 minutes will turn off by itself? That's the only problem left now.