RGB mod of CRT Panasonic TC-14S20RDF on MX-3 chassis

[Kvazikvark]

So far, this will serve as a continuation of the discussion about the RGB modification of the Panasonic TC-14S20RDF CRT from the original thread.

Summary
I thought this RGB mod would be a cakewalk, so I copied a solution from one user on this forum. However… like another user, I also ended up with a dark picture. After reading the datasheet, I now realize that the OSD chip uses RGB signals at a much higher voltage level (around 0–3.2 Vp-p) compared to standard RGB (0–0.7 Vp-p). This explains why the image was too dark.

Now I need to adjust the RGB signal to achieve a proper picture.

In this thread, I’ll document my progress as I work through the project.

Currently, I am setting up a workspace for an oscilloscope and waiting for all the necessary parts to arrive. Among the items that haven’t even been ordered yet, the only thing left to source is an isolation transformer. I’m looking for a factory that can manufacture one for me.

PS
English isn’t my native language—though I understand everything written or spoken in it perfectly, I haven’t dedicated enough time to studying grammar yet, so my phrasing tends to be clumsy. I decided to try running my text through Deepseek, and… I loved the results! I’ll probably keep drafting messages this way from now on.

[ahkek89]

So far, this will serve as a continuation of the discussion about the RGB modification of the Panasonic TC-14S20RDF CRT from the original thread.

Summary
I thought this RGB mod would be a cakewalk, so I copied a solution from one user on this forum. However… like another user, I also ended up with a dark picture. After reading the datasheet, I now realize that the OSD chip uses RGB signals at a much higher voltage level (around 0–3.2 Vp-p) compared to standard RGB (0–0.7 Vp-p). This explains why the image was too dark.

Now I need to adjust the RGB signal to achieve a proper picture.

In this thread, I’ll document my progress as I work through the project.

Currently, I am setting up a workspace for an oscilloscope and waiting for all the necessary parts to arrive. Among the items that haven’t even been ordered yet, the only thing left to source is an isolation transformer. I’m looking for a factory that can manufacture one for me.

PS
English isn’t my native language—though I understand everything written or spoken in it perfectly, I haven’t dedicated enough time to studying grammar yet, so my phrasing tends to be clumsy. I decided to try running my text through Deepseek, and… I loved the results! I’ll probably keep drafting messages this way from now on.

Hello, were you able to address this? I also have the same issue on this chassis.

[Kvazikvark]

Hello, were you able to address this? I also have the same issue on this chassis.

Hello, unfortunately I haven't had time to continue the project practically, there are only theoretical outlines. I planned to make a simple op-amp amplifier for each of the RGB signals and adjust the Vp amplitude using trimmer potentiometers. That should work, and as for gamma, it's unlikely that I'll need to adjust it since the microcontroller should handle it itself, from what I've read.

[Kvazikvark]

Hello, were you able to address this? I also have the same issue on this chassis.

By the way, I had an interesting observation when I was working with an old Trinitron. Its RGB colors were similarly very dark, just like on this small Panasonic. Adjusting the G2 screen/speed-up voltage solved the problem. Ideally, it should be calibrated using a 100 IRE pattern with a colorimeter, but you can also try to do it by eye. You need to make sure the black remains black (doesn't turn grey), while the areas that should be visible become visible (and white should be white).

However, I must warn you: this adjustment must be performed on a powered-on tube. Otherwise, it will take millions of years. But a powered-on CRT is lethally dangerous. If you want to try it, find where the G2 adjustment is located on your set (it could be on the flyback transformer or on the neck board; you can check the service manual). Under no circumstances use a metal screwdriver and keep your distance from the anode wire—it can arc and shock you from up to 5 cm away. If you are not sure, it's better to adjust it with the power off, or better yet, not to touch it at all.

[MarkOZLAD]

IIRC the last time I modded an MX3 I had to adjust screen voltage to see the mist fpga after it was showing the SNES perfectly.

[ahkek89]

IIRC the last time I modded an MX3 I had to adjust screen voltage to see the mist fpga after it was showing the SNES perfectly.

Were your videos outputting correctly? Any changes in brightness during different scenes of the gameplay?

[MarkOZLAD]

I don’t recall, it was quite some time ago.

I know with the MX4M the black levels are never correct.