I've had a Magnavox TS2582 C101 for a couple of years and finally decided to see if I could mod it for RGB. From factory it only has RF, composite, and S-Video. The chassis according to the label on the back of the case is 25R505-00AA
I cannot find the regular owner’s manual, and I do not own a remote for it.
However, I found the service manual for this range of chassis models here:
https://ia801308.us.archive.org/32/item ... 207538.pdf
The service manual does not list the specific type of jungle IC, so I had to open it up.
I removed the main PCB and had to desolder and pry open an EMI shield to find the jungle chip, a TDA8369. It's hard to find much documentation on this chip, but I found a short spec sheet:
https://datasheet4u.com/datasheet/ETC/TDA8369-770219
I hesitate to call it a full datasheet, and it’s a poor quality scan with black blotches making some areas hard to see. However, on the last page I unfortunately did spot the line under Features: "RGB-control circuit with digital OSD input with intensity control"
So, SOL, right? But I had a lot of time to waste today and I started looking up mods for other jungle chips of the TDA836X and TDA837X range (using crtdatabase.com) and it seemed like all the rest had analog inputs. So I decided to poke around some more.
The chip has RGB inputs from a separate OSD chip, but I did not see any coupling capacitors on the schematic or when physically inspecting the board. (There were capacitors to ground)
So, not trusting the crappy datasheet, I decided to hook up my oscilloscope to the Green line between the microprocessor and the TDA8369 Jungle chip.
Luckily, the scope did not blow up which I think verifies that it is not 'hot chassis'.
Here is what the signal looks like when I am adjusting the volume (and thus triggering the OSD)
Immediately I thought this looked digital and felt disappointed, but I realized an analog signal here would just basically show Green as either On or Off depending on the position in the scan line… so is this analog? I am still not entirely sure of myself. Can anyone chime in?
As an aside, in the service manual there was a short blurb saying "Caution: The RS Chassis incorporates a "HOT" ground system. Always use a separate isolation transformer when applying power to the ex-posed chassis."
(I wasn’t sure if that applied to my specific model, and it would be odd I thought for a TV from 1995 with S-Video to be made like this, but it's possible. However mine is not "RS" and I am not sure what chassis that statement is even referring to. Studying the schematic more closely and it looked like the AC was in fact isolated through a transformer. There was continuity between the existing RCA jack shields and various grounds on the main board, including pin 13 GND on the actual jungle chip. I also did a diode test on between the two sides of the AC plug and the RCA jack shield, both prongs and both polarities and it was all reading as no connection. So I risked it, and so far seems to be fine.)
TLDR:
I am trying to figure out if that signal is analog and if/how I should proceed to attempting a RGB mod, preferably muxed but switched if need be.