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Dek's RGB to Component Transcoder

6 months ago 406
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Description

Dek's RGB to Component Transcoder (17/5/2020) - This schematic and PCB has been designed to convert a video signal from RGB format to Component (Y,Y-r, Y-b) format. This signal is typically used for retro video game consoles and arcade boards.

You can find the public github here: https://github.com/dekkit/RGB-to-Component-Transcoder

Background Component video can be found in modern CRT TVs to support better picture quality from DVD players and Set Top / Cables boxes. It is found on many later model CRTs and LCD screens.

NOTE - This schematic will not upscale a 240p signal. Many LCD tvs will not display a 240p picture through Component video in!

This schematic was intended to be used for consumer CRT TVs as another way to support RGB (particulary in arcade setups where crt tubes are getting harder to find/replace). It is designed to be used as an external device (outside of the system) rather used internally.

Includes

  • Audio pass through (to support the development of custom retro console cables)
  • Additional variable resistors (trim pots) to attenuate incoming RGB signals and create an all-in-one style plug (useful for per retro console customisations ie snes pal).
  • Composite Video to Composite Sync (to extract csync from normal composite video, in case a system does not natively output csync - like snes pal)
  • Mostly use through-hole components to make it easier to assemble (except for the THS amp - which will require careful soldering skills).

Design Note(s)

  • Designed primarily as an external unit, input are assumed to be 75 ohm signals (hence the use of 75R resitors to ground). You may need to remove these if you intend to adapt this pcb and use it intenally.
  • For arcade boards you will need to attenuate the RGB signals to a level that your consumer CRT will accept (it 3-5V p-p down to 0.7V p-p) - this can be done altering the resistor values (google arcade to scart for more info and recommended adjustments and warnings as does incorrectly it may damage your hardware).

Materials

  • Used 1/4 watt resistors 5% (either ceramic or metallic - though many TV mods use ceramic, so use cermic if possible)
  • Low voltage maerials is acceptable (ie I've been using 6.3v for the electrolytic cap without any issues)
  • Monolythic ceramic capacitors were used (104, and 105 - again use metallic ones if ceramic is unavailable).

Initial successful testing (on version VA01 19/4/2020):

  • Snes Pal, Dreamcast NTSC, Arcade 60-in-1 Jamma PCB

Warning

  • No Warranty provided /use at own risk. Will not be held liable for any damage (its free after all!).
  • Use quality video cables (cheap imported video cables have weird resistance values which create all sorts of video interferences - keep cables short too!).

Please share, clone, improve and share again (pay it forward) - that way we can all benefit. This was based on many designs found on the web using the BA7230 chip and from plenty of own my trials and testing the quality of outputs.

Documents

Sheet_va3

PCB_VA03

BOM

ID Name Designator Footprint Quantity
1 LM1881 U3 LM1881 1
2 THS7374 U2 TTSOP-14 1
3 10u C5 CAP-D3.0XF1.5 1
4 0.047u C4 RAD-0.2 1
5 1u C12,C14,C13,C11,C8,C7,C6 RAD-0.2 7
6 0.1u C1,C2,C3,C9,C10,C15,C16 RAD-0.2 7
7 BA7230LS U1 SZIP24 1
8 75 R2,R3,R8,R1,R9,R10,R13 AXIAL-0.3 7
9 1k R4,R7 AXIAL-0.3 2
10 2M2 R5,R6 AXIAL-0.3 2
11 680k R11 AXIAL-0.3 1
12 1K2 R12 AXIAL-0.3 1
13 R_3386P_US RP1,RP2,RP3 RES-ADJ-TH_3386P 3

Attachments

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Comments (2)

RTG//DOGamingEnterprises Reply

This seems like a good circuit, but can I modify this circuit. I feel like it is missing some connections.

dekkit Reply

@valdezramses03 It is designed as an open and accessible base circuit to provide for the many possible use cases and range of connectors out there.    If you need a version with specific sockets, feel free to message me directly.

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