Figured out a sync switch. Thanks!

I'm looking to build a multi input RGB/supergun box. The one problem is that I will be using a dedicated line for both sync/compsite(to have sync stripped from) and a game system switch box. So some systems will have a dedicated sync and some won't. I want to use a LM1881N chip but I am unsure how to wire it up.

I was looking at maybe just wireing it to kill the power to it, but I don't know if it will allow a sync signal pass though when powered down. I'm not sure of any other way wire it, but if anyone has a better idea or doesn't understand how i'm presenting it please let me know.

-Drewmantrivia

Bump. Anyone? D-Lite maybe? I got the idea from seeing one of his superguns on his site.

Drewmantrivia

Drewmantrivia said:

Bump. Anyone? D-Lite maybe? I got the idea from seeing one of his superguns on his site.

Drewmantrivia

Click to expand...

Don't loose hope...

I'll get you some info tonight if nobody else does....

I forgot about this thread. I just don't have the time right now.

I'll try to do describe here without the aid of pics.

When looking at the LM1881 such that you can read the text, you have the following:


+5V.......blank........connect.......blank
......................................\
........................................\
..........................................\
............................................\
..............................................\
................................................\
sync out.......sync in........blank.......Gnd/connect


On the sync in have a 0.1 uF cap between the sync in on the IC and the wire.

Where I have "connect" above, you need to connect these two points with a 680k Metal film resistor and a 0.1 uF cap in parallel. This in addition to having the ground go to that lower right pin.

Are you doing this for systems or a supergun, or both?

Yeah, I can't figure out what exactly the purpose of this "RGB/supergun" box is. It seems like any JAMMA board will not need this sync splitter and any game system will require it?

I'm betting both.

I just did a supergun for someone that has an extra DB-9 male connector on the back. This is designed for INPUT, not output. On the port are RGB and R/L audio inputs as well as +5V and Ground. By putting in those inputs the user can run the encoder as well as utilize the RGB pots and audio attenuation and switches to output component or S-Video without the need for buying additional encoders or even for plugging in the supergun's power.

D-Lite said:

I'm betting both.

I just did a supergun for someone that has an extra DB-9 male connector on the back. This is designed for INPUT, not output. On the port are RGB and R/L audio inputs as well as +5V and Ground. By putting in those inputs the user can run the encoder as well as utilize the RGB pots and audio attenuation and switches to output component or S-Video without the need for buying additional encoders or even for plugging in the supergun's power.

Click to expand...

That's what I was thinking.... But few systems need stripping anymore...

norton9478 said:

That's what I was thinking.... But few systems need stripping anymore...

Click to expand...

"anymore"

Retro systems do though. Turbo

Ok, first off My bad on explaining this.
I understand how the LM1881N chip works. I checked out the info from gamesx.com What I am looking to do is build a Supergun AND a RGB to component/s-video/compsite box for my retro game systems using JROK's new board. I figure to kill 2 birds with two stones for what it is going to cost.

I want to standardize the all the connections so it can use RCA jacks all around for the game system cables and Jamma boards connections. I will have several systems that i will have to hookup so this will be alot easier for me this way. And i can use a simple game switch box with component jacks like this one http://hardware.gamespot.com/Story-ST-x-2011-x-x-x

The back of my box will look like this minus the audio jacks.


Now some systems have Sync outputs and some don't. For the layout I want to do i can only have the one jack for both Sync and/or a Composite signal to be stripped. So that is why I need the switch. ALso seeing that D-Lite did it for one of his makes me think that it could be needed AND possible to do. I'm just not sure on the execution of how to do it.

Now to shoot my self in the foot. I would test all this out on my own, BUT i can only afford so much at a time so i have bits and pieces of of the whole thing so I can't actively test anything yet. I just want to have all my info straight so I can get everything i need and just sit down one weekend and put it together. Which reminds me D-Lite I need to talk to you about power supplies and buying one from you.

Any Ideas or thoughs on this using a Sync that can be switched or could the LM1881N be passive in sending a Sync signal through when powered down?

Thanks for the help and intrest
Drewmantrivia

The reason to install the LM1881 is that many systems DON'T have a straight sync signal output. BUT, they all have a composite output, which is what you need the LM1881 for in terms of stripping sync from the composite.

And yes you need it switched. Don't rely on passive throughput of the sync through the LM1881.

Cool. But I still need some help with my original question. How do I wire something like this with a switch and still keep my RCA jacks the way they are?

I checked in with Lawrence at Gamesx and he said to just leave the LM1881N chip on all the time and feed it Sync and Composite and it won't matter. It seemed to be a bit simplfied of an answer.

That is why i'm asking here and mostly to D-Lite. How could it be done. I have looked and have not seen any diagrams or how-to's on the web to explain it. It just may be so simple that i'm missing it for myself but I just don't see a good way to do it. Knowing tha that you may have done something similar to this is why i'm asking.

If you can lead me in the right direction or give me a hand please PM me or send me a e-mail. Drewman21@hotmail.com

Thanks

Just use a SPDT switch.

The middle pin is the output. One of the outer pins is the regular Compsite sync line. the other pin is the composite sync (stripped from composite video) line.

norton9478 said:

Just use a SPDT switch.

The middle pin is the output. One of the outer pins is the regular Compsite sync line. the other pin is the composite sync (stripped from composite video) line.

Click to expand...

Ding.

You also should probably wire another switch SPDT on the imput to the LM1881 circuit.

One has composite sync in (Where available), the other has Composite video in.

Some PCB/Encoder combos work better if you run the Composite sync through the LM 1881 circuit first.

I love diagrams and MSpaint!

So if i'm hearing you right is this what i'm looking at for a hookup?

[/URL][/IMG]

Just using the one RCA jack for both Sync and Composite sync.

I not sure what another spdt switch to the LM1881 chip would offer me for options but let me know if I did this correct to what you guys are saying.

And really guys thanks for the help so far. If you ever get to Fargo ND i'll buy both you guys a drink!

-Drewmantrivia

Yep.

You guys rock! Thanks D-Lite and Norton. I'll let you know how it goes.

-Drewman21

Fargo,

Isn't that where Roger Maris is from????

Anyhow, That's some iLl fuckin MS Paint... I've seem some where the RCA jacks looked like Hams....

I've seen some where

Drewmantrivia said:

I love diagrams and MSpaint!

So if i'm hearing you right is this what i'm looking at for a hookup?

[/URL][/IMG]

Just using the one RCA jack for both Sync and Composite sync.

I not sure what another spdt switch to the LM1881 chip would offer me for options but let me know if I did this correct to what you guys are saying.

And really guys thanks for the help so far. If you ever get to Fargo ND i'll buy both you guys a drink!

-Drewmantrivia

Click to expand...

Hello,

I want to make this LM1881 Sync separater as well. Where can I find 680k Metal film resistors and 0.1 uF caps? Online store prefered due to my location - Radio Shack? Any help would be greatly appreciated.

SeaWolf69

SeaWolf69 said:

Hello,

I want to make this LM1881 Sync separater as well. Where can I find 680k Metal film resistors and 0.1 uF caps? Online store prefered due to my location - Radio Shack? Any help would be greatly appreciated.

SeaWolf69

Click to expand...

www.digikey.com
www.jameco.com


Radio Shack will have 0.1 uF cap (ceramic disc)

D-Lite,

Thanks for the links. Can you tell me exactly which model 680k Metal film resistor and 0.1 uF cap? There seems to be different variations and I'm not sure which ones to get? I'm looking through jameco.

SeaWolf69

SeaWolf69 said:

D-Lite,

Thanks for the links. Can you tell me exactly which model 680k Metal film resistor and 0.1 uF cap? There seems to be different variations and I'm not sure which ones to get? I'm looking through jameco.

SeaWolf69

Click to expand...

I'll see if I can find the part numbers for you but how about these options:
- I send you the resistor and cap (2 resistors, 3 caps, so you have an extra of each)
- I send you the whole circuit with the LM1881N prebuilt (no switch though)

PM me if you want that. It'll be much cheaper than buying and shipping from any vendor.

never mind