How to Determine TTL Sync

[Tempest_2084]

I decided to get brave and crack open some of my SCART cables. I apologize in advance for the crappy pictures, but they're not an easy area to get to so I had to make due with a crappy phone and a flashlight. Hopefully these pictures can help determine if they have the correct resistors and capacitors to get 75 Ohm sync.

Genesis Model 2 - Looks like there's just one resistor and nothing else


SMS - Looks like three resistors on the RGB lines and another one across some pins



SNES - Looks like three caps and a resistor



NES (RGB modded) - Same as the SNES one.. Three caps and a resistor



Can we tell anything from these pictures? If so I can crack open the rest of my cables and take pictures. I appreciate all the help everyone has been giving me so far.

[Josh128]

Is the color code on those resistors Green, Black, Orange, Red? 4 total, in that order? Hard to make it out.

[Tempest_2084]

Is the color code on those resistors Green, Black, Orange, Red? 4 total, in that order? Hard to make it out.

I think so, I'd have to open it again to be sure. What should they be? I have a better quality picture somewhere.

[Guspaz]

C-sync and TTL are not mutually exclusive terms. You keep saying "csync or TTL" like they are

C-sync refers to the *type* of sync (composite sync meaning horizontal and vertical sync combined (not to be confused with sync on composite video))

TTL refers to the *amplitude* of the sync signal, its lower voltage counterpart is "video level sync" AKA 75 ohm sync

Ok so it's not CSync it's 75 Ohm sync? Gotcha.

No.

csync 75ohm
csync TTL

These are both two things that exist. There is 75ohm csync and TTL csync.

Look at it another way: csync just means there's no video signal riding along, it tells you nothing about what kind of sync it actually is.

[Tempest_2084]

C-sync and TTL are not mutually exclusive terms. You keep saying "csync or TTL" like they are

C-sync refers to the *type* of sync (composite sync meaning horizontal and vertical sync combined (not to be confused with sync on composite video))

TTL refers to the *amplitude* of the sync signal, its lower voltage counterpart is "video level sync" AKA 75 ohm sync

Ok so it's not CSync it's 75 Ohm sync? Gotcha.

No.

csync 75ohm
csync TTL

These are both two things that exist. There is 75ohm csync and TTL csync.

Look at it another way: csync just means there's no video signal riding along, it tells you nothing about what kind of sync it actually is.

Ok I think I understand now. I just wish there was an easy way to tell what my cable is doing. I guess even looking at the inside of the SCART head doesn't help all the time because the needed components might be in the console plug side of the cable. I think I'm just going to assume all my cables are 75ohm csync and take my chances with the 5X Pro.

[TooBeaucoup]

Ok I think I understand now. I just wish there was an easy way to tell what my cable is doing. I guess even looking at the inside of the SCART head doesn't help all the time because the needed components might be in the console plug side of the cable. I think I'm just going to assume all my cables are 75ohm csync and take my chances with the 5X Pro.

While there's obviously no guarantee, I think the main cable makers that everyone goes to have been doing the 75ohm cables over the last few years. I think you'd only have gotten TTL if you specifically asked for it.

[Tempest_2084]

While there's obviously no guarantee, I think the main cable makers that everyone goes to have been doing the 75ohm cables over the last few years. I think you'd only have gotten TTL if you specifically asked for it.

I'm thinking the same thing.

[matt]

Ok I think I understand now. I just wish there was an easy way to tell what my cable is doing. I guess even looking at the inside of the SCART head doesn't help all the time because the needed components might be in the console plug side of the cable. I think I'm just going to assume all my cables are 75ohm csync and take my chances with the 5X Pro.

I'd be willing to bet that your cables all use composite video for sync. That's how the SCART standard was designed - its primary purpose was to display composite video, with the RGB lines as a way to add closed captioning or other overlays. Using SCART to display pure RGB video is kind of a hack and there's no reason for a standard European SCART cable to use csync.

None of your cables have an inline resistor on pin 20, which is what would be necessary to attenuate your consoles' sync signal to 75 ohm levels. The resistor that all your cables have is for the blanking voltage, which is what tells a PAL television to switch to RGB instead of composite (this is a remnant of SCART RGB's close caption origins). The resistors on the SMS cable are on the RGB lines, rather than the sync signal.

Looking at the photos of your cables, they are all low end cables with no shielding. These cables are made in Asia and were designed for low budget PAL television owners, not tech savvy retro gamers with fancy scalers and pro monitors. I've never seen a cable like this that was wired for Csync. While they are not the best cables in the world, they should work fine for your purposes and you should be fine using them with your Retrotink.

[mikechi2]

Ok I think I understand now. I just wish there was an easy way to tell what my cable is doing. I guess even looking at the inside of the SCART head doesn't help all the time because the needed components might be in the console plug side of the cable. I think I'm just going to assume all my cables are 75ohm csync and take my chances with the 5X Pro.

I'd be willing to bet that your cables all use composite video for sync. That's how the SCART standard was designed - its primary purpose was to display composite video, with the RGB lines as a way to add closed captioning or other overlays. Using SCART to display pure RGB video is kind of a hack and there's no reason for a standard European SCART cable to use csync.

None of your cables have an inline resistor on pin 20, which is what would be necessary to attenuate your consoles' sync signal to 75 ohm levels. The resistor that all your cables have is for the blanking voltage, which is what tells a PAL television to switch to RGB instead of composite (this is a remnant of SCART RGB's close caption origins). The resistors on the SMS cable are on the RGB lines, rather than the sync signal.

Looking at the photos of your cables, they are all low end cables with no shielding. These cables are made in Asia and were designed for low budget PAL television owners, not tech savvy retro gamers with fancy scalers and pro monitors. I've never seen a cable like this that was wired for Csync. While they are not the best cables in the world, they should work fine for your purposes and you should be fine using them with your Retrotink.

Good eye and yup those look like Alibaba specials with composite video sync, which is technically correct but sadly no shielding. Will work just fine with the 5x.. maybe with some noise and hum compared to the good stuff but still far better than composite. I say use them and play the damn game for now.

[Tempest_2084]

Ok I think I understand now. I just wish there was an easy way to tell what my cable is doing. I guess even looking at the inside of the SCART head doesn't help all the time because the needed components might be in the console plug side of the cable. I think I'm just going to assume all my cables are 75ohm csync and take my chances with the 5X Pro.

I'd be willing to bet that your cables all use composite video for sync. That's how the SCART standard was designed - its primary purpose was to display composite video, with the RGB lines as a way to add closed captioning or other overlays. Using SCART to display pure RGB video is kind of a hack and there's no reason for a standard European SCART cable to use csync.

None of your cables have an inline resistor on pin 20, which is what would be necessary to attenuate your consoles' sync signal to 75 ohm levels. The resistor that all your cables have is for the blanking voltage, which is what tells a PAL television to switch to RGB instead of composite (this is a remnant of SCART RGB's close caption origins). The resistors on the SMS cable are on the RGB lines, rather than the sync signal.

Looking at the photos of your cables, they are all low end cables with no shielding. These cables are made in Asia and were designed for low budget PAL television owners, not tech savvy retro gamers with fancy scalers and pro monitors. I've never seen a cable like this that was wired for Csync. While they are not the best cables in the world, they should work fine for your purposes and you should be fine using them with your Retrotink.

Good eye and yup those look like Alibaba specials with composite video sync, which is technically correct but sadly no shielding. Will work just fine with the 5x.. maybe with some noise and hum compared to the good stuff but still far better than composite. I say use them and play the damn game for now.

Thank you all for the info. I feel better now, but I think probably should upgrade. What brand/company do you all recommend for cables? I know HD Retrovision gets high praise, but they're all component cables. Who makes the best SCART cables? Well at least good quality ones that don't run $70+

It looks like Retro Access has a new line of cheaper fully shielded cables called Fortaflex. I think these might work for what I want:

https://retro-access.com/collections/fortraflex

I assume all my consoles will work with 75 Ohm csync? Other than my NES (the first RGB mod that was created) and my TurboDuo (another early mod) none of them are modded with anything unusual.

EDIT: I have a ton of questions now. I think I might start a new thread since this no longer has anything to do with TTL Sync.

[matt]

Retro acces cables are easily the best quality you can buy, but it's overkill for 90% of gamers. Their fortraflex cables will definitely be good enough. IMO Insurrection is your best bet; their stuff is well made, affordable, and most importantly it's usually in stock.

If your cable is properly shielded, there's no need to use csync unless you have a device that requires it, such as an Extron unit or an old computer monitor.

[ldeveraux]

Retro acces cables are easily the best quality you can buy

Not if you bought them in 2018. I think I bought 7-8 of the highest quality cable from them and had issues with 3 of them. Mostly bad soldering on the inline resistor, but unless the quality has improved in 3 years...

[Tempest_2084]

IMO Insurrection is your best bet; their stuff is well made, affordable, and most importantly it's usually in stock

Yeah I was thinking about going with them as long as their cables were decent. Bob seems to think they were ok and almost indistinguishable from the Retro Access ones in terms of picture/audio quality. While I want good quality cables, I'm not going to zoom in 500 times and inspect each pixel. I'm honestly more concerned about audio buzz and highly noticeable fringing/interference patterns than anything else.

[Tempest_2084]

Being the masochist that I am, I decided to open up my two cables that go from one scart switch to the other and the one that goes to my TV. These cables are a bit odd as they appear to have a loose pin wired that gets wedged in between the metal shielding and the SCART connector itself (it popped out when I took the picture). I assume this is for ground, but what a weird way to do it. They look like the typical cheap thin gauge wires, but they appear to have *some* shielding in the actual cable itself. Are these cables crap as well? Should they be replaced? I'd hate to upgrade the rest of my cables and have them do no good because the final cable is crap.

Here's a picture of it (ignore the lovely finger, I had to try and hold it together while taking the picture)

[matt]

That loose pin is just a way to connect the shell (aka pin 21) to ground.

The real test of whether or not a cable is good enough is to try it in your setup. That cable does have some external shielding, but there's still the potential for interference between the video and audio lines. Once you get your 5x, try your consoles with and without the switcher and the intermediate cables and you should be able to figure out if there's enough signal degradation for it to be a problem.

[Tempest_2084]

Ok I'll wait for the 5X to get here before replacing this cable since it might actually be ok.

[Gunstar]

Probe the video and sync pin to ground voltage on an opened up SCART connector while running the 240p suite on a full IRE white screen.

Just to clarify the SCART doesn't need to be attached to the TV, just that it's outputting a white screen from the source?

[eightbitminiboss]

Probe the video and sync pin to ground voltage on an opened up SCART connector while running the 240p suite on a full IRE white screen.

Just to clarify the SCART doesn't need to be attached to the TV, just that it's outputting a white screen from the source?

Needs to be plugged in to complete the circuit.

[Gunstar]

Probe the video and sync pin to ground voltage on an opened up SCART connector while running the 240p suite on a full IRE white screen.

Just to clarify the SCART doesn't need to be attached to the TV, just that it's outputting a white screen from the source?

Needs to be plugged in to complete the circuit.

Thanks!

[Retrorunner]

I am currently lost which RGB cable can be used with the Retrtink5x. Would be thankful for some advice about my cables. I own two cables for

1.SNES PAL RGB cable with sync stripper which does not have 75ohm
(I am using this cable with my PAL SNES Dejitter Borti mod)

2.Mega Drive 2 PAL RGB cable with composite video and no 75ohm

So both cables doesn't use TTL sync BUT what about the missing 75ohm?
...and what would happen if you use TTL sync with the Rx5? Does it take some time until the Rx5 stops working?

[Guspaz]

As a general rule, using TTL sync with any product that does not support it will mean that, whether it works or not, it will cause highly accelerated degradation to components as they are being fed five times the expected voltage.

Sending any electronic device multiple times the voltage they're expecting is never a good idea.

[awe444]

Suppose I have a cable or device that is outputting TTL sync via a BNC connector, and I want to attenuate it to consumer level voltage without soldering anything. Is a “75 ohm terminator” (example pictured below) a plug and play solution to accomplish such attenuation?

[Retrorunner]

As a general rule, using TTL sync with any product that does not support it will mean that, whether it works or not, it will cause highly accelerated degradation to components as they are being fed five times the expected voltage.

Sending any electronic device multiple times the voltage they're expecting is never a good idea.

Thanks. After some research I came to the conclusion my SNES (PAL) RGB cable with sync stripper AND 470ohm should be OK for the retrotink5x:

https://www.retrogamingcables.co.uk/SYN ... B-STRIPPER

https://www.retrorgb.com/syncinscart.html

..but I am still not sure about the Mega drive 2 cable which uses composite video and has no 75ohm.

[matt]

Suppose I have a cable or device that is outputting TTL sync via a BNC connector, and I want to attenuate it to consumer level voltage without soldering anything. Is a “75 ohm terminator” (example pictured below) a plug and play solution to accomplish such attenuation?

No, this is just a BNC connector with a 75 ohm resistor connector to ground. It's used for the output side of monitors or test equipment to bring the signal down to the proper voltage level.

Consumer TVs have a 75 ohm resistor to ground on each video input. But with professional monitors, it's often necessary to daisy chain several displays together or to route the signal through other instruments for calibration purposes. Using a single terminator at the end of the chain allows multiple devices to run off of one input signal without dropping the voltage level too much.

Somebody should make a male to female BNC dongle with a 470 ohm resistor built in. It would be very useful.

[matt]

Thanks. After some research I came to the conclusion my SNES (PAL) RGB cable with sync stripper AND 470ohm should be OK for the retrotink5x:

https://www.retrogamingcables.co.uk/SYN ... B-STRIPPER

https://www.retrorgb.com/syncinscart.html

..but I am still not sure about the Mega drive 2 cable which uses composite video and has no 75ohm.

Any SCART cable that uses composite video for sync does not need any additional component on the sync line. Composite video is what SCART TVs were built to display.

[mikechi2]

As a general rule, using TTL sync with any product that does not support it will mean that, whether it works or not, it will cause highly accelerated degradation to components as they are being fed five times the expected voltage.

Sending any electronic device multiple times the voltage they're expecting is never a good idea.

Thanks. After some research I came to the conclusion my SNES (PAL) RGB cable with sync stripper AND 470ohm should be OK for the retrotink5x:

https://www.retrogamingcables.co.uk/SYN ... B-STRIPPER

https://www.retrorgb.com/syncinscart.html

..but I am still not sure about the Mega drive 2 cable which uses composite video and has no 75ohm.

Sync strippers inside a SCART cable is an awful idea. For my stuff please use sync on composite or sync on luma.

[Retrorunner]

As a general rule, using TTL sync with any product that does not support it will mean that, whether it works or not, it will cause highly accelerated degradation to components as they are being fed five times the expected voltage.

Sending any electronic device multiple times the voltage they're expecting is never a good idea.

Thanks. After some research I came to the conclusion my SNES (PAL) RGB cable with sync stripper AND 470ohm should be OK for the retrotink5x:

https://www.retrogamingcables.co.uk/SYN ... B-STRIPPER

https://www.retrorgb.com/syncinscart.html

..but I am still not sure about the Mega drive 2 cable which uses composite video and has no 75ohm.

Sync strippers inside a SCART cable is an awful idea. For my stuff please use sync on composite or sync on luma.

Ok thanks. What about Composite Video? (Mega Drive 2)

[eightbitminiboss]

That's what sync on composite is.

Edit: To clarify, there's composite sync (CSync), and sync-on-composite otherwise known as composite video sync.

https://en.wikipedia.org/wiki/Component_video_sync

[Retrorunner]

Ok got it. thanks. If its sync on luma or sync on composite in both cases it should be 75ohm terminated (for the use with the Retrotink5x) right?

[eightbitminiboss]

Ok got it. thanks. If its sync on luma or sync on composite in both cases it should be 75ohm terminated (for the use with the Retrotink5x) right?

In most, if not all cases composite video and luma are already at the correct voltage and shouldn't need anything extra on the line as explained before in this thread. CSync is the problem because it's normally way higher and intended for devices that can handle it (i.e., professional video equipment) and properly terminated. Hence why if Csync is your only option it has to be pulled down with a resistor to a safer voltage level for things like the Retrotink.