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Thread: Lets try to hack RGB into an old Toshiba CRT.

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    Lets try to hack RGB into an old Toshiba CRT.

    Hi people. Have this old Toshiba TV Chassis used in an old MAME cab that has since been restored to original hardware. This TV has a crappy picture and thought it would be a good candidate to try and feed RGB into the OSD IC like Michael Moffitt describes on his website

    So far I've identified the OSD IC under an RF shield. It appears to infant have RGB outputs as well as the blanking pin
    that will be tied to presumably 5v to get the whole picture to fill the screen.

    So right now it's kinda late and just debating on what console would be easiest to feed RGB from just as a test setup. Maybe a model 1 Genesis as I already have one apart.

    Anyway just thought a live walk through of this might be useful for others in either case of the outcome. Maybe some of you have already done this and have some input or tips on the subject. Apparently it isn't always as easy as it seems
    but we will try and see what happens.

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    First, see if you can find the service manual for the TV and identify the Jungle IC (the large IC that performs mixing of input signals). That'll be your best source of info.

    If you can't find it, at least you've identified the microcontroller's RGB outputs for the OSD. You can try taking red, green, or blue out of circuit from the microcontroller output, and giving your own signal there. If you leave everything intact, that will let you see your RGB signal "through" the letters of the OSD. That will be a sign of progress.

    Regarding the video you linked to, here's my shmups thread where I did the RGB input mod successfully to the same TV, the Sony KV-27FS100. I sought out that TV because I saw that video and thought, "It looks so good in that video when it's working. It must be possible!".

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    Hi Mike, what a small interwebs it is. Alright so I'll try tapping into the actual jungle IC next time as this CRT chassis may have been damaged during removal or when I forgot to hook up a ground wires from the chassis to the neck board. Kinda sad but this chassis was on it's way out anyway with it's bad picture.

    When you tap the jungle did you still use the OSB chip bank pin to get the picture to fill? Was the best way to wire it up pretty much like this but use 100nf caps like you ended up with? Did you lift the RGB pins or the blanking pin from the pcb? Thanks for the info

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    Yes, the 100nF / 0.1uF caps worked best as that's what my Jungle IC's database wanted. I took the RGB pins out of circuit, and then had a large switch to change between OSD RGB + blanking, and my RGB + 5V for "always blanking".

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    Been busy but got caught up on some stuff that needed to get done today. Will probably have some more time for this tomorrow.

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    So I cracked open a Sony this time around mainly because the original Toshiba isn't firing up anymore. I found the video ic data sheet and found the RGB output pins on 31 33 and 35. I tapped the G output line with it still connected to the chassis pcb and ran a jumper to the component green input after cutting its pcb trace for the center connection so it now runs straight to pin 33(G) on the jungle ic. Then we wired up ground on the Genesis A/V with a 75ohm resistor in between, finally sync is tied to composite center pin.

    When I turn on the TV the picture is all green but there is no graphics and it looks like the sync is off. This picture tried to best capture the effect but just imagine the whole screen is green with that horizontal lines going through it. I'm not sure what the problem is, maybe using the wrong RGB pins?

    On another page on that video data sheet it shows the OSD pins as 57 58 and 59 and I'm assuming FAST BLK is the blanking pin as it's called out as such on another similar data sheet. I guess I'll try to tap these pins and see what happens. Let me know what you think Mike thanks.

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    Without looking too carefully it looks like the ICs you've found are the OSD generators (microcontrollers) and not the Jungle IC. The Jungle IC in a Sony TV is almost always going to be a Sony chip starting with "CXA" in the name. I'd hunt for one of those first.

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    So on that Sony I was tapping into the RGB out to the guns, not the OSD. I also found what I thought were the OSD RGB pins but when they were lifted from the pcb the osd still showed fine. Gave up on that one for now.

    I moved on to another Toshiba tube and found the service manual for it. I've terminated the OSD RGB inputs on the chroma ic and tied green into the G pin just to see if I can at least get one color to work first. I've also disconnected the Fast BLK and tied it to 5v to fill the screen. I'm getting a full green screen with a lot of waves in it now. Wondering if I'm hooking up the Genesis model 2 correctly.

    This is pretty much how I have it wired up except I'm just using the green line for now and there is no 10uf cap because figured I could just add that later. What do you think Mike? could it not be working because of the missing 10uf?

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    You may need the capacitor to restore black level. I had success with a 0.1uF cap, but you can try various values.

    For now, I would use the Genesis composite for sync, as the sync output from a Genesis is not buffered and may not sync.

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    I switched over to the composite pin on the av out and its syncing differently now but still no graphics. I wonder if maybe my chroma chip is digital levels or maybe is working with YUV color space. Is there a practical way of telling this?

    Edit: Ah dang this thing is digital RGB. On to the next potential tube.
    Last edited by darknezz19; 02-11-2016 at 12:05 PM.

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    Got it. Had to terminate to ground with 100 ohms to get the colors right, these pics are also w/o the 100nf caps. I'll try with them and see what it shows as well to compare but for now its working

    http://imgur.com/a/FzNr7

    Mike did you ever find a more practical way of shifting the image over without the service menu because of the composite syn delay?

    Edit: saw your bit about using Luma on Svideo, I'll try that.
    Last edited by darknezz19; 02-12-2016 at 12:56 AM.

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    I use C-Sync, giving it to the S-video input. There was a pin on the s-video jack I had to tie to ground to enable the input, which is normally used for detecting if a cable is plugged in. That may be related.

    Without the 100nF caps, you might find some systems will have incorrect levels based on overall screen color and the border color. For me, Super Nintendo, NESRGB, and PC Engine all had some problems without decoupling capacitors.

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    Amazing job! I've seen this done before and I've always been fascinated by it. Quality looks just as you would expect! RGB goodness.

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