Can't get horizontal or vertical lock on CRTTV trough RGB to SCART  - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: June 20, 2022, 01:38:13 am
content: So I'm trying to add RGB outputs to my Sega Megadrive 2 console, I found the RGB encoder on the board, it's a KA2198DB, datasheet link here:https://pdf1.alldatasheet.com/datasheet-pdf/view/92867/SAMSUNG/KA2198BD.htmlbut I don't really get how this RGB encoder works, at first I saw the RGB out pins, saw that the RGB in pins actually went somewhere, so I soldered some wires to 330uF caps and to the scart connector, I got a small picture (not sure if it's just garbage), that was rolling both vertical and horizontal, and seemed to change the speed of rolling (not sure if it was the TV or the sync was changing)then I read some stuff online and saw someone mention "connect the C-Sync line to the IN pin of the IC not the out", so I did that, and it didn't change anything.now, I'm assuming C-Sync is horizontal sync right?, also do I need to mix in the vertical sync signal in the sync in pin of the scart connector or no?but later looking further, the RGB-in pins of the RGB encoder just go to 22nF caps and 2.2k resistors to ground. what confuses me is why I have anything on the TV if it isn't hooked up.actually the RGB output works, just dont have sync, idk where those pins connect to the ASIC but they mustI have pin 8 connected to +5V from the console and pin 16 trough a 100 ohm resistor to +5VI saw some pinouts call pin 16 blanking and had it shown to be connector to the horizontal sync line, do I need to do this or is it something else?oh and pin 17 of the IC (the Y trap) isn't connected to anything, there is a spot for a capacitor to ground from pin 17 but it isn't installedand for reassurance, the console does work in composite modepin 6, fsc.in is connected to ground trough a 10uF capacitorpin 7 is connected to ground for PAL mode

author: Kyle_from_somewhere
author_rank: Regular Contributor
timestamp: June 20, 2022, 03:42:07 am
content: In my own experience (I haven't owned one for about 13 years), the MD2 already has RGB output, and only needs a cable that you can buy ready made. Where are you reading this stuff you are doing?C-Sync means "Composite sync" - a combined signal that does both horizontal and vertical.When sending RGB over SCART, it's sent in addition to the mundane CVBS Composite Video that's on Pin 20. The TV uses the composite video signal as it's source of sync.Some equipment does not like using composite video as it's source of sync, so a chip like LM1881 would be used to remove the video part of the CVBS signal. But if you are just using a plain TV you don't need to do any stuff like that.

author: Benta
author_rank: Super Contributor
timestamp: June 20, 2022, 10:10:28 am
content: Check the green signal, you might find the sync there.

author: Kyle_from_somewhere
author_rank: Regular Contributor
timestamp: June 21, 2022, 02:29:39 pm
content: Quote from: ELS122 on June 20, 2022, 08:20:05 amBlanking is SCART pin 16, should connect to a voltage source 1V or higher. Usually, this is 5V with a little resistor on it

author: Benta
author_rank: Super Contributor
timestamp: June 21, 2022, 06:23:58 pm
content: Lots of nice pins on the SCART connector, but when you look at what's actually connected inside a TV, VCR or DVD player (Service Manuals), you'll see that it extremely rare that RGB is even connected (This is an EU market view, but SCART is an EU thing).CVBS, R+L audio and control signals are about it. All the rest are unconnected/non-functional.

author: Kyle_from_somewhere
author_rank: Regular Contributor
timestamp: June 22, 2022, 03:41:07 am
content: I completely disagree with that assessment. With VCRs, yes they had no RGB output, but I never come across a scart TV that didn't have working RGB in. What would be the point?Adding RGB is extremely cheap. Just detect some voltage on pin 16 then switch three signal lines. So simple you don't need a switching chip, or a relay or anything. Just diodes, resistors, dc blocking caps, and an inverter gate.