RGB modding a Hot Chassis TV using optocouplers

[StarquestMan]

Hi! I have started a RGB mod project a while ago on a hot chassis Sanyo TV with AV inputs from around 98' or so and was wondering if anyone might be able to help me get the circuit dialed in so it does not have the faint smear lines in the picture. This is my first time modifying a circuit like this and I have learned quite a bit but need some pointers on how to get the last 10-20 percent sorted out for a perfect picture. I have not found much info on how to do what I am trying to achieve since this has a live chassis but am wanting to do it not only for my own accomplishment but hopefully anyone else who has a live chassis TV will be able to learn. I seem to come across quite a few TVs, even later ones, that are similarly set up with either no AV inputs or ones that have them but are isolated via optocouplers. Here is what I have so far. I noticed that there is one flaw in my schematic where the 20k trimmer connects to the optocoupler. it should be connected to pin 5 instead of 6. it is connected to the high side of the 1k resistor so the only thing connected to pin 6 is the 120 ohm resistor. The optocoupler is an HP/Agilent HCPL4503 and the NPN transistor is a BC548. When I connect a .1 uf cap across pins 5 and 8 of the optocoupler like the datasheet says I get a very smeared picture so I left it disconnected, that and my circuit does not match the example circuit so I don't think it applies anyway.

[Syntax]

That Sanyo does not seem like a hot chassis TV.

Seems like a candidate for an OSD mux, id inject the RGB and blanking to pins 33,34,35,36 of IC101.

The inlines for OSD are 5600k and the terminations are 560R, put that in Marks calculator.

https://diagramas.diagramasde.com/otros ... -27580.pdf

[cyborc]

It's definitely looks like a hot chassis TV to me...no hot/cold markings on the board, and the RF box is not directly connected to the back of the TV.

I have a sharp hot chassis tv that I plan to mod eventually but I was just going to use an isolation transformer...

[StarquestMan]

Oh yea thats the TV! I totally spaced adding the model number in my first post, it is a DS27580. Now that my post is up I cant seem to see my pictures that I linked but hopefully everyone else can see them. I got rid of the coupling caps for each channel before the driver transistor for the optocoupler since I figured out that my scart cables already have some and the picture smearing has cleared up greatly. The TV has a border marked out for the av section and everything inside is isolated with optocouplers and a little isolation transformer to power everything inside. also the TV does not appear to have a switching power supply of any sort, it seems to just be rectifying and regulating the line voltage, unless it is using the flyback as a sort of isolation transformer? I think the circuit is pretty close to being dialed in now, although the image is a bit soft. I also will need to come up with a sort of circuit to "mute" the optocouplers output when the osd signal is present, im sure this can be done using the blanking signal coming from the CPU to kill power to the output side of the optocoupler?

[Syntax]

Just mix the osd and rgb inputs. Should work well enough.

[ElBartoME]

It just blows my mind that there were still hot chassis TVs being manufactured in 1999. WTF.