Build Your Own Arcade Controls Forum
Software Support => GroovyMAME => Topic started by: bluetrain on September 23, 2019, 11:07:43 am
-
For my GM setup I have a sony trinitron that is working beautifully with rgb-scart for quite some time. I got an opportunity to buy a Sharp ( 54DT-25S )CRT cheap and why not?
When I looked in the instruction manual found online http://www.usersmanualguide.com/sharp/televisions/37_54dt-25s it pictured the scart and R G B pins and corresponding ground seemed to be "correct" according to the schedule. So I thought the tv should have RGB scart?
However, when I hooked it up, I got no picture. I have only one scart and no options in the meny to change anything. And here comes the really strange part: When I open the options meny I can see a small portion of the real screen behind the settings, like in the backdrop. Closing the meny and screen is black again.
Anything (within reason) I can do get the TV working?
-
That sounds like someone RGB modded the TV and used the OSD menu to jumper the RGB signal. This is how most people take a TV that didn't originally have an RGB input and convert it. But this is mostly here in the U.S. as Europe had SCART and RGB on most sets. Where are you located?
-
Along with or near to the RGB pins on the jungle chip, there should be a pin for fast blanking. In this case it is pin 38, labelled "FB". This pin needs to be fed from +3 to +5VDC to blank other signals and show RGB. At the moment, it looks like this pin is connected to the original OSD FB line from the set's microcontroller chip. This blanks the display at specific points and pulses RGB in, to display the text of the menus. But instead of the menus, you're seeing your RGB signal. So the RGB lines are connected, but not the FB.
It *might* be more complicated than this, it's possible someone has muxed the OSD badly, or a wire has come loose. There are jungle chips that blank outputs on higher voltages and other things. If you get stuck, there's a dedicated RGB hacking thread on the Shmups forum - https://shmups.system11.org/viewtopic.php?f=6&t=56155
Most important of all, remember to be safe around live equipment, and that even powered-down a CRT might hold dangerous charge for days.
-
I´m located in Europe. Thanks a lot guys for your clarification and answer. This will be to much out of my comfort zone so I will try to find another TV with RGB-scart instead.
-
All euro scart TVs work in RGB, none require a mod. That doesn't men they all share the same specs though.
So the issue might be elsewhere, but it could be difficult to find out what it is.