Genesis:Video Output Notes

All Genesis/Mega Drive consoles are capable of outputting RGB, and all except for the two Wondermega models have it available in stock form. Every model also outputs composite video, which would have been the default choice alongside RF during their heyday.

RGB Cable Components

In all Genesis/Mega Drive consoles, the amplified RGB signals coming from the video encoder chip are directly wired to the AV output connector and do not have any of the required components connected to them. Each signal needs a 75 ohm resistor (which lowers the brightness to a proper level) and a 220 uF 10V capacitor (to filter out DC offset), and these must be added to the cable itself. The composite video signal can be used for sync, and requires no extra components since it is already buffered inside the console.

All RGB cables that use composite sync should have a 470 ohm resistor and a 220 uF 10V minimum capacitor with the positive leg facing the console on the sync line, which is pin 7 for the model 1 and pin 5 for systems with a 9-pin mini-DIN connector. The voltage rating should not be below 10V.

32X Jumper Cable

The Sega 32X video jumper cable does not need any components in it, as it simply passes through RGB from the host console into the 32X, where it is mixed with the 32X's own video output and sent through its own connector. Some aftermarket jumper cables do this perhaps a little too well, as they also pass through the 5V pin. This can be dangerous for both the 32X and attached Genesis/Mega Drive as it can backfeed 5V from the Genesis into the 32X. More information on this can be found here.

French Model 1

Model 1 Mega Drive consoles sold in France (model numbers 1600-09 and 1601-09) only output RGB and lack the supporting components necessary to output composite video. In addition, they output 75 ohm composite sync whereas all other Mega Drives output TTL sync. These were also packaged with a special SCART cable (Adapteur R.V.B.), but can be made compatible with standard SCART cables by jumping the sync output to the unused composite video pin on the DIN connector. A special adapter for French consoles is also available for owners of HD Retrovision cables.

Video Encoder Notes

Sega went through a variety of video encoder chips with the Genesis hardware, each performing the same basic task of amplifying RGB out and also converting it to composite video for use with most displays.

Sony CXA1145

This is the initial encoder that Sega chose for the Genesis and continued to use until the mid-1990s. It outputs relatively mediocre composite video, and is made worse on model 1 consoles with odd "rainbow banding" that covers the entire screen. The CXA1145 outputs separate chroma and luma signals, but they are intended to be fed back into the encoder itself to generate composite video and were not designed to drive proper S-video output. It can be modified to output S-video though, and the original Wondermega console does feature this video output while making use of the 1145. Two variants of the CXA1145 exist, the CXA1145M which is an SMD chip and the CXA1145/CXA1145P which is through-hole.

The CXA1145 is found in the following consoles:

• All model 1s except for VA6.8 revisions (CXA1145/P for VA0 through VA6.5, CXA1145M on VA7)
• Some VA0 through VA1 US model 2s, especially those manufactured in Japan during 1993 (CXA1145M)
• Some VA3 model 2s (CXA1145M)
• Most Japanese Mega Drive 2s (CXA1145M)
• Wondermega (CXA1145M, the only console to output S-video using this encoder)
• JVC X'Eye (CXA1145M)
• Mega Jet (CXA1145M)

Sony CXA1645

During 1994, Sega switched from using the CXA1145 to its successor, the CXA1645. It is an improved version of the 1145, utilizing less components and can also drive proper S-video output (only requiring a 75 ohm resistor and 220 uF capacitor for both chroma and luma). Composite video is also improved over the 1145, with a slightly sharper and more saturated picture.

The CXA1645 is found in the following consoles:

• Some VA2 through VA3 model 2s
• US and Asian VA4 model 2s
• Aiwa Mega CD
• Genesis Nomad
• Genesis 3

Fujitsu MB3514

The MB3514 is a pin-compatible clone of the CXA1145 that is more commonly found in PAL Mega Drive II consoles, but did see use in some NTSC consoles. Its composite video quality is comparable to the CXA1145, but is slightly noisier with some noticeable vertical lines on certain color backgrounds. It also exhibits significant color bleed and fringing on NTSC model 2 consoles. The MB3514 also does not output a 75 ohm composite sync signal on pin 11 like Sony encoders. However, one major advantage of the MB3514 is that it can output proper S-video, only requiring a 75 ohm resistor for each signal.

The MB3514 is found in the following consoles:

• VA6.8 model 1
• All VA0 through VA1.8 PAL Mega Drive IIs
• Some VA1 and VA1.8 US model 2s
• Some Japanese Mega Drive 2s
• Asian Mega Drive 2
• Wondermega M2 (the only console to output S-video using this encoder)
• CDX/Multi-Mega

Samsung KA2195D

Only found in US model 2s, the KA2195D is generally regarded as the worst encoder found in any Genesis console. Although RGB output is generally fine as always, composite video output is fairly poor with noticeable vertical "jailbars" and other artifacts. Much of this can be cleaned up by installing a small PCB which fixes the subcarrier signal going to the encoder or by performing an entire encoder swap. The KA2195D also does not have chroma and luma outputs, meaning an S-video mod is not possible with this encoder.

The KA2195D is found in the following consoles:

• Most VA0 through VA2 US model 2s
• Some VA2.3 and VA3 model 2s

ROHM BH7236AF

This encoder is a pin-compatible clone of the CXA1645 and is only found in PAL VA4 Mega Drive II consoles. Its output quality is essentially the same as the CXA1645 as well.