Syntax wrote:Your 5v blanking line was back feeding into the micron and activating it?
Diode should sort that.
Dropping the screen voltage to get ideal brightness doesn't seem right.
Does 240p test suit color bars look ok or black crush?
Double check your termination total or test .5vpp video if so.
I have found a 19 in Samsung CRT TV. Model is txh1973. Chassis is K15A, Chroma is TA1282N and OSD Zilog 3757, wiring diagram is exactly the same as the TV megasdkirby has modded, the only difference is the OSD chip which is different. Otherwise the line resistor is 7.5kohm. ground resistors is 1.2kohm. RU10 680ohm is there as well.
I previously modded another 19 in Samsung CRT TV using the OSD Mux method developed by MarkOZLAD for the 8bit guy. It worked straight from the bat.
This one has obviously the same symptoms as megasdkirby indicated in his mod. Screen is too bright. Where does it come from and is there an alternative to modifying the flybackwheel?
I tried to snip the OSD entirely and inject RGB signal straight to the chroma, with various inline resistors value and ground resistor values to see if I could get anything.
Any ground resistor value of 75 ohm or below : The image is too dim (btw if I jump RU10 I got the same dim screen and the OSD becomes invisible. this is one difference I got with megasdkirby. I can't explain why, but this is consistent with my findings when I snip the OSD. maybe it is because the OSD chip is different. Another finding is even if I snip RGB line from OSD I can still have access to the menu! I guess the signal is coming from the CCD line through the common ground line? no problem here though)
Any ground resistor of 240 ohm or above (or even no ground resistor at all), the image is too bright and some details in the picture get lost.
Anything in between is not satisfactory either (I tried 83,100,120 ohm) . So basically I can’t find a voltage divider arrangement that seems to work. Theoretically a 75ohm ground resistor should give me 0.7Vpp.
To rule out any other option, I tested various values for the inline resistor (including 1200ohm), this does not change anything, which is expected as I entirely sniped the OSD, so there is no more voltage divider there.
Picture from my first samsung TV. Crisp, beautiful, I want to repeat that one.
Picture from this txh1973 model, meh ...
Thx for anyone insight, to help me understand. And if flybackwheel is the only solution, then at least I will understand why.
Here-below is the traced PCB