sync on green signal

By Mumbly

Resident (49)

Mumbly's picture

30-04-2019, 11:53

Hi all,

I've recently purchased a SONY LMD1410, which is, a Professional monitor, with the intention to use the RGB signals (not composite). This monitor requires the CSYNC signal must be mixed with the green signal (Sync on green: SOG).

My turbo R (A1ST) outputs RGBS on the din 8 RGB connector, so I need to inject the S (pin 4 on din 8, pin 20 on scart) in the green signal.
to do it so I used a circuit with a polarized capacitor (100ufd) and a resistor of 680 ohms like explained in this article

sync on green

which , partially works, meaning that the colors are good, but from time to time the hsync on top of the screen unhook, with the effect that 20% of the top screen is not well on sync.

I've seen another circuit based on transistor:

https://www.raphnet.net/electronique/sync-on-green/SyncGreen...

Anybody has experienced such issue ?
I didn't tested yet the transistor solution

Login or register to post comments

By Wild_Penguin

Hero (541)

Wild_Penguin's picture

01-05-2019, 11:22

Is the monitor this one?

Are you sure it can not accept separate sync trough the composite video input? Seems weird a monitor would require sync-on-green, bot I suppose it is possible. I have no experience with those circuits....

By Mumbly

Resident (49)

Mumbly's picture

01-05-2019, 21:48

Thanks Wild_Penguin for your interest

Indeed, it’s the lmd 1410, the main difference between the lmd 1410 and 1420 is the ext sync
option, the 1410 doesn’t have this option unfortunately.
You think if I put csync on composite video line 1 and r g b ...
But the component/rgb and line 1 cannot be selected together.
But I can test, I´ll keep you posted on my investigation results

By Wild_Penguin

Hero (541)

Wild_Penguin's picture

01-05-2019, 22:59

Yes, I looked trough the user manual, and noticed the difference. It's is a longshot, but worth a shot still, to see if it works that way. It could be an undocumented feature in the monitor!

By bore

Expert (115)

bore's picture

02-05-2019, 09:18

The LMD-1420/1410 Service Manual could also be worth having a look at.
If I were to guess the 1410 uses the same PCB as the 1420 for the BA board but with ADG779 replaced with a 0 ohm resistor.
If you can find it it should be possible to remove it and solder in your own external sync signal. (But that removes the sync on green option.)

But it is probably easier to just try the transistor version in your first post.

By Mumbly

Resident (49)

Mumbly's picture

02-05-2019, 16:48

Perhaps the csync is a rvbs signal (composite signal of rgbs) this may affect
The sync result, does a turbo r A1 st is providing a pure csync (composite of h and vsync) or a rvbs on the din 8 pin 4??

By Mumbly

Resident (49)

Mumbly's picture

02-05-2019, 17:20

True, I prefer, in a first instance, not changing the monitor pcb.
But I will have a look to what you have explained in the instruction manual, I missed that part

By Mumbly

Resident (49)

Mumbly's picture

04-05-2019, 21:32

Problem solved: the resistor of 680 ohms is the issue.
680 ohms is the value to transform a TTL signal to a SOG compatible 0.3VPP signal , TTL voltage level is about 5 to 3.3v , the Turbo R outputs a Csync signal of 1.8 vpp, not a TTL signal VGA like, the resistor value is then too high and must be replaced by a 470 Ohms resistor.

Thanks for your collaboration, guys: without having read carefully the service manual, I wouldn't have found the solution Smile