+-^CrossBow^- Posted August 5, 2023 Share Posted August 5, 2023 (edited) I thought it might be a good idea to have a dedicated topic on the various cable setups that folks might be using that work or don't work with the current 1.0 revision of the 7800GD. Confirmed to work with 7800GD AV out: Rad2x for Sega MD/Genesis model 2. Works out of the box without issue and provides great results. Requires a micro HDMI to full HDMI cable that doesn't come included. https://www.retrogamingcables.co.uk/sega/mega-drive-2/SEGA-MEGA-DRIVE-2-GENESIS-2-32X-HD-RAD2X-HDMI-480P-CABLE Hyperkin Genesis to HDMI - Requires external power. Works well but does crush the darker colors quite a bit. https://www.amazon.com/Hyperkin-HDTV-Cable-Genesis-Sega/dp/B07RW8R3QF?ref_=ast_sto_dp Kaico SEGA SATURN 2x" HDMI-Converter (Info provided by @Emwee) https://kaicolabs.com/product/kaico-sega-saturn-2x-line-doubler-hdmi/ Sega Mega Drive 2 / Genesis 2/ 32X Component YPbPr cable - This provides YUV component output but might not work on all TVs. https://www.retrogamingcables.co.uk/sega/mega-drive-2/Sega-Mega-Drive-2-Genesis-2-32X-Component-YPbPr-cable-240p Standard Sega Mega Drive 2 / Genesis 2 RGB to SCART cables should also work but results will vary from TV to TV and scaler to scaler. As an example, I've not gotten any to work through my OSSC, but they did work fine on my RetroTink2x SCART and are reported to work great on the Retrotink5x Pro. Here are some links for some that are of good quality: https://www.retrogamingcables.co.uk/sega/mega-drive-2/sega-mega-drive-2-sega-genesis-2-rgb-av-scart-cable-tv-lead https://insurrectionindustries.com/product/sega-genesis-model-2-rgb-scart-cable/ - Insurrection Industries is located in the US Edited November 22, 2023 by -^CrossBow^- Adding additional options 4 Quote Link to comment Share on other sites More sharing options...
atarimonster Posted August 8, 2023 Share Posted August 8, 2023 Hi, I am trying to get the best picture on my PAL-Maschine as well. And The Hyperkin Cable just work out of the box with very good picture on PAL-Machines. In Germany You can buy it here: https://dragonbox.de/de/produkte-fur-sega-megadrive/megadrive-genesis-mastersystem-hdmi-kabel.html Greetings from Germany 1 Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted August 8, 2023 Author Share Posted August 8, 2023 4 hours ago, atarimonster said: Hi, I am trying to get the best picture on my PAL-Maschine as well. And The Hyperkin Cable just work out of the box with very good picture on PAL-Machines. In Germany You can buy it here: https://dragonbox.de/de/produkte-fur-sega-megadrive/megadrive-genesis-mastersystem-hdmi-kabel.html Greetings from Germany Yes I mentioned the Hyperkin Cable set in my original post. It does work and work well, but I've noticed that a few of the much darker hues are being crushed in the output and just appear as black. It mainly seems to affect the background graphics in a few games where it doesn't show up or is hardly visible. But again, I suspect most folks aren't going to notice or care when the rest of it looks as good as it does. Quote Link to comment Share on other sites More sharing options...
mimo Posted August 9, 2023 Share Posted August 9, 2023 I bought the RGB Scart version from herehttps://www.retrogamingcables.co.uk/sega/mega-drive-2/sega-mega-drive-2-sega-genesis-2-rgb-av-scart-cable-tv-lead nice quality and a great image on my old LG Plasma TV Quote Link to comment Share on other sites More sharing options...
marauder666 Posted August 9, 2023 Share Posted August 9, 2023 Tested quite a few different TVs in last couple of weeks. A forum member sent his PAL machine which was crashing after a while. Having no idea if its the console, GD7800, or anything else, got him to send console, GD7800 and the no-name brand SCART cable he was using. Crashing was due to the voltage regulator, sorted that (a long story in itself). Did some testing on various TVs and monitors, couldn't get a sync'd picture on any of the flat panel TVs, added a resistor to the SCART cable to lower sync to a level similar to what it would be in a composite video signal, and had more luck. When working the picture looked pretty good. TVs were all connected by SCART, no scalers. Working. Sony 32" LCD (2006), Samsung 40" LCD (2012?), Sony TV/VCR combo, Sony PVM (1994), Sony BVM (1988), owner's Panasonic LCD works too, but a bit offset to the left. Not working. Toshiba 43" (2007), Sony 17" non-hdmi (2004?), GBS control scaler into LaCie 19" VGA monitor (maybe 50hz into a VGA display causing bad sync). 1 Quote Link to comment Share on other sites More sharing options...
SainT Posted August 9, 2023 Share Posted August 9, 2023 3 minutes ago, marauder666 said: Did some testing on various TVs and monitors, couldn't get a sync'd picture on any of the flat panel TVs, added a resistor to the SCART cable to lower sync to a level similar to what it would be in a composite video signal, and had more luck. This is an issue with the current batch of 7800GD using composite video based sync cables. The sync ends up being ~1.2V, which is slightly above spec. Ideally use a csync based cable, which is fine, but is actually a little low at about 180mv, or add a 75R resistor inline for the composite sync based cables. This is being rectified with the next batch of carts with both sync methods coming in at about 700mv (give or take) depending on the video cable used, which is what is considered as a good reference voltage for sync. Quote Link to comment Share on other sites More sharing options...
marauder666 Posted August 9, 2023 Share Posted August 9, 2023 One I forgot, a friends, Panasonic Plasma, probably around 12 years old, didnt work either. This has terrible analogue signal handling though and was expected. I guessing here, but maybe some of these older LCD TV's with SCART sockets really need composite video on the SCART as per the spec, rather than Csync. Quote Link to comment Share on other sites More sharing options...
SainT Posted August 10, 2023 Share Posted August 10, 2023 14 hours ago, marauder666 said: I guessing here, but maybe some of these older LCD TV's with SCART sockets really need composite video on the SCART as per the spec, rather than Csync. I think the biggest issue is the sync is very jittery, it's only in the realm of something like 700ns per frame, but that's more than enough to cause issues with many TV's. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 12, 2023 Share Posted August 12, 2023 (edited) Hello, @SainT I tried a CSync cable from 2 well known companies(RA/RGC) on my Framemeister and neither worked. I tried them on a Retrotink scart2comp and they both work, but with a lot of jitter at the top of the screen looked like a sync issue. It also takes a very long time for anything to show up on screen so I'm not able to get to the update screen. Anything I can modify inside of the cart to resolve this? My main scaler is the Framemeister. Edited August 12, 2023 by Icelvlan Quote Link to comment Share on other sites More sharing options...
xeex Posted August 12, 2023 Share Posted August 12, 2023 I'm using a $14 RGBS cable from Amazon on a Sony PVM, and it's excellent. It even came with 4 RCA to BNC adapters. (This is not a component cable.): TNP Sega Genesis RGB/RGBs Adapter Cable Connector Quote Link to comment Share on other sites More sharing options...
SainT Posted August 12, 2023 Share Posted August 12, 2023 17 hours ago, Icelvlan said: Hello, @SainT I tried a CSync cable from 2 well known companies(RA/RGC) on my Framemeister and neither worked. I tried them on a Retrotink scart2comp and they both work, but with a lot of jitter at the top of the screen looked like a sync issue. It also takes a very long time for anything to show up on screen so I'm not able to get to the update screen. Anything I can modify inside of the cart to resolve this? My main scaler is the Framemeister. Some bending at the top of the screen in the first few visible lines is normal, compatibility with specific frame capture devices I cannot help with unfortunately. I use a Tink5xp and then into an HDMI capture device myself. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 13, 2023 Share Posted August 13, 2023 5 hours ago, SainT said: Some bending at the top of the screen in the first few visible lines is normal, compatibility with specific frame capture devices I cannot help with unfortunately. I use a Tink5xp and then into an HDMI capture device myself. What about the fix you mentioned above? Are we able to change the current resistors on this PCB? Would be easy to do. Quote Link to comment Share on other sites More sharing options...
SainT Posted August 13, 2023 Share Posted August 13, 2023 (edited) 6 hours ago, Icelvlan said: What about the fix you mentioned above? Are we able to change the current resistors on this PCB? Would be easy to do. Using a csync (not composite video sync) cable should be fine. There is nothing you can change on the PCB, it has required more rework than this to fix the issue fully. If you want you can change the 470R resistor in the video cable to a 75R, this will bring the sync up to about 700mv, which is more common. It’s currently at about 180mv, which also works fine, but is a little low. The main issue with devices not locking on the sync is that there is jitter in the sync by a few cycles each frame. There is nothing that can be done about this and this is the main compatibility issue with modern scalers and capture devices. And I should mention that the bending seen in the first few lines of the screen is nothing to do with any sync voltage levels or resistors, it’s how I deal with the jitter. I’ve found scalers and capture devices deal better with small jitter per hsync rather than large jitter per vsync. So at the beginning of the frame a dump all the collected jitter cycles into the hsync pulses. In general, this seems to work quite well, but you get get some bending for a few scanlines. Edited August 13, 2023 by SainT 1 Quote Link to comment Share on other sites More sharing options...
mmervine Posted August 13, 2023 Share Posted August 13, 2023 Thanks to the tip from CrossBow, I purchased the Hyperkin Genesis-HDMI cable and can confirm that it works well with my 7800GD! 2 1 Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 13, 2023 Share Posted August 13, 2023 10 hours ago, SainT said: Using a csync (not composite video sync) cable should be fine. There is nothing you can change on the PCB, it has required more rework than this to fix the issue fully. If you want you can change the 470R resistor in the video cable to a 75R, this will bring the sync up to about 700mv, which is more common. It’s currently at about 180mv, which also works fine, but is a little low. The main issue with devices not locking on the sync is that there is jitter in the sync by a few cycles each frame. There is nothing that can be done about this and this is the main compatibility issue with modern scalers and capture devices. And I should mention that the bending seen in the first few lines of the screen is nothing to do with any sync voltage levels or resistors, it’s how I deal with the jitter. I’ve found scalers and capture devices deal better with small jitter per hsync rather than large jitter per vsync. So at the beginning of the frame a dump all the collected jitter cycles into the hsync pulses. In general, this seems to work quite well, but you get get some bending for a few scanlines. Unfortunately this is my main genesis cable, so I don't really want to change the value. Is there not a resistor that can be changed on the PCB to bring up voltage on the output of the cart? I don't have an issue changing an smd resistor. Quote Link to comment Share on other sites More sharing options...
SainT Posted August 13, 2023 Share Posted August 13, 2023 1 hour ago, Icelvlan said: Unfortunately this is my main genesis cable, so I don't really want to change the value. Is there not a resistor that can be changed on the PCB to bring up voltage on the output of the cart? I don't have an issue changing an smd resistor. No, it has required an additional 5v level shifter. If I were you I’d be inclined to change the resistor in the md2 cable and find out if it makes any odds, if it doesn't, it’s a moot point. If it sorts your issue then you could bodge in a level shifter, or I’d be happy to replace the cart for you when I have a suitable replacement. I’m reasonably confident it will make no odds when using a csync cable. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 14, 2023 Share Posted August 14, 2023 (edited) 4 hours ago, SainT said: No, it has required an additional 5v level shifter. If I were you I’d be inclined to change the resistor in the md2 cable and find out if it makes any odds, if it doesn't, it’s a moot point. If it sorts your issue then you could bodge in a level shifter, or I’d be happy to replace the cart for you when I have a suitable replacement. I’m reasonably confident it will make no odds when using a csync cable. I'll give it a try sometime this week and let you know Thanks! Edited August 14, 2023 by Icelvlan Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 14, 2023 Share Posted August 14, 2023 (edited) Hi @SainT, Just did a quick test putting a 75ohm resistor on sync and it worked right away on my Framemeister. Edited August 14, 2023 by Icelvlan Quote Link to comment Share on other sites More sharing options...
SainT Posted August 14, 2023 Share Posted August 14, 2023 7 hours ago, Icelvlan said: Hi @SainT, Just did a quick test putting a 75ohm resistor on sync and it worked right away on my Framemeister. Nice, thanks for the update! Are you replacing an existing 470R resistor with 75R? If so, that's interesting, I didn't think this would have much effect. But equally I'm pleased as the latest PCB revision will help with compatibility. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 14, 2023 Share Posted August 14, 2023 Yes replacing a 470 resistor with 75. What would be the fix on the PCB though? Quote Link to comment Share on other sites More sharing options...
SainT Posted August 14, 2023 Share Posted August 14, 2023 4 minutes ago, Icelvlan said: Yes replacing a 470 resistor with 75. What would be the fix on the PCB though? Cut the traces going to the mini DIN CSYNC and composite video pins then bodge in a 3.3V->5V level shifter onto the CSYNC output from the FPGA and feed the 5V signal into the CSYNC pin on the mini DIN. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 14, 2023 Share Posted August 14, 2023 (edited) Silly question but I see 1 resistor in path and and 1 going to ground. Couldn’t I just change one of those? I didn’t take measurements of these. Edited August 14, 2023 by Icelvlan Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted August 14, 2023 Author Share Posted August 14, 2023 25 minutes ago, Icelvlan said: Silly question but I see 1 resistor in path and and 1 going to ground. Couldn’t I just change one of those? I didn’t take measurements of these. Not sure where you are seeing that? On my 7800GD the trace directly off the encoder goes straight to the Sync on pin5 and there is a tiny trace connecting pin5 to pin4. It is pin4 (Usually the composite video signal) that is being used by many of the known cables for c-sync. There might be other resistors etc before that IC chip but not from the IC directly to the pins on the AV out. Quote Link to comment Share on other sites More sharing options...
SainT Posted August 14, 2023 Share Posted August 14, 2023 1 hour ago, Icelvlan said: Silly question but I see 1 resistor in path and and 1 going to ground. Couldn’t I just change one of those? I didn’t take measurements of these. 18 hours ago, SainT said: No, it has required an additional 5v level shifter. Quote Link to comment Share on other sites More sharing options...
Icelvlan Posted August 14, 2023 Share Posted August 14, 2023 The resistors are before the encoder Quote Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.