Where can I tap a sync signal for s-video?

[thesteve]

the 4558 is way too slow (tried it)
a transistor amp can be built that works well.
the 1881 also works, but must have a capacitor input, duo to the offset in the chip

[lastcallhall]

the 4558 is way too slow (tried it)
a transistor amp can be built that works well.
the 1881 also works, but must have a capacitor input, duo to the offset in the chip

Hm. I put a 0.1uF cap on the 1881 composite pin and it didn't change anything.

I think tomorrow or sometime soon, I'm going to rebuild the circuit from scratch. This can't be that complicated.

I just hate having to undo everything and start all over again... >=(

[thesteve]

a good way to confirm the sync sig is to hook it to a tv.
the tv will see the sync as a black picture (not rolling)

[lastcallhall]

a good way to confirm the sync sig is to hook it to a tv.
the tv will see the sync as a black picture (not rolling)

So, here's what I did, and my observations:

I took the csync signal from the 6260 and added it to the composite out jack on the system and the image stabilized, albeit in B/W, which leads me to believe that the sync signal is good on the system, I just need to rework the CXA1645 circuit - something must have gotten messed up somewhere.

Parent/teacher conferences tonight, so I doubt I'll get to this until morning, but I'll figure it out...

[thesteve]

the 1645 needs the sync to be TTL levels (0 to 5V switching)
you have about 180mV off the chip

[lastcallhall]

the 1645 needs the sync to be TTL levels (0 to 5V switching)
you have about 180mV off the chip

OK, so what would you suggest I do? Is using an op amp for the sync going to be enough? Should I use the RGB/SYNC shown here:

http://www.gamesx.com/grafx/pce_rgb.jpg

then feed it into the chip?

I'm kinda lost right now and not sure which way to go.

I'd appreciate the help.

[thesteve]

nope that circuit wont work at all

[SignOfZeta]

OK, seriously, there are a lot of s-video modded Duos out there. Someone must know how to do it.

Also, my question got buried back there: will a Neobitz work directly from the Hu chip or do I need something else? I also have a JRok.

[thesteve]

ok i dont know anything about neobits...........checking......................nope
not enough info on the jrok.

most have used the 1881 sync stripper on the composite output.
the TE uses a common emitter transistor amp, which causes +sync of TTL levels.
the best way is comp sync from the chip--->common emitter transistor amp----->logic inverter------>encoder ic

[grahf]

SignOfZeta, I've always heard that the JRok kits don't work for whatever reason, and the guy who makes them doesn't know why. Never tried one myself, though. I have no idea about the Neobitz.

lastcallhall, seriously, stop jumping around all kinds of hoops and just go with the LM1881. It's pretty much the standard way to do this, and it works. Everyone uses it for everything. Here is a picture of a circuit from the gamesx page:

Original link: http://www.gamesx.com/misctech/lm1881.htm


It's incredibly easy, and you only need like 50 cents worth of components. You are ONLY going to use pins 1, 2, 4, 6 & 8.


Composite out is pin 1, which is what you're after. This goes into your CXA1645.

Composite Video goes into pin 2, NOT composite sync from the HU6260. The easiest place to get composite video is off the back of the original AV out plug. Just solder a wire to the right place on the inside of your Duo. You need to put an 0.1uf capacitor in-line, which looks like this: http://www.newpages2u.com/images/12882347761ef4fa1d3bb9fa56b4ee022142f88ecc.jpg and will say "104" on it.

Pin 4 goes to ground. Make sure the LM1881 and your CXA1645 circuit share the same ground. The grounds for everything should end up connected to the ground on your Duo's motherboard.

Pin 6 is the "set" pin. Not reset. You need another 0.1uf capacitor, the same one as above. You also need a 680kohm resistor. Make sure the value is correct. You hook both of these parts to pin 6, then the other side of them goes to ground. The same ground as everything else.

Pin 7 is 5v input. You can use any value up to 12v, but it's easy enough to get 5v off of the Duo motherboard, and I personally use 5v.


Good luck, and if this still doesn't work please post pictures of what you have currently made.

[lastcallhall]

SignOfZeta, I've always heard that the JRok kits don't work for whatever reason, and the guy who makes them doesn't know why. Never tried one myself, though. I have no idea about the Neobitz.

lastcallhall, seriously, stop jumping around all kinds of hoops and just go with the LM1881. It's pretty much the standard way to do this, and it works. Everyone uses it for everything. Here is a picture of a circuit from the gamesx page:

Original link: http://www.gamesx.com/misctech/lm1881.htm


It's incredibly easy, and you only need like 50 cents worth of components. You are ONLY going to use pins 1, 2, 4, 6 & 8.


Composite out is pin 1, which is what you're after. This goes into your CXA1645.

Composite Video goes into pin 2, NOT composite sync from the HU6260. The easiest place to get composite video is off the back of the original AV out plug. Just solder a wire to the right place on the inside of your Duo. You need to put an 0.1uf capacitor in-line, which looks like this: http://www.newpages2u.com/images/12882347761ef4fa1d3bb9fa56b4ee022142f88ecc.jpg and will say "104" on it.

Pin 4 goes to ground. Make sure the LM1881 and your CXA1645 circuit share the same ground. The grounds for everything should end up connected to the ground on your Duo's motherboard.

Pin 6 is the "set" pin. Not reset. You need another 0.1uf capacitor, the same one as above. You also need a 680kohm resistor. Make sure the value is correct. You hook both of these parts to pin 6, then the other side of them goes to ground. The same ground as everything else.

Pin 7 is 5v input. You can use any value up to 12v, but it's easy enough to get 5v off of the Duo motherboard, and I personally use 5v.


Good luck, and if this still doesn't work please post pictures of what you have currently made.

Good deal, that sounds workable. Thanks!

Quick question, though - I'm doing this on an american TG-16, not my Duo. Would the video signal from VIDEO A23 on the EXP port suffice for pin 2 on the LM 1881?

[thesteve]

yes

[lastcallhall]

 

Still didn't work.

Here are some closeups of what I'm looking at:

Here's the LM1881. Solid green is video in from pin A23 on the EXP port, striped green is sync out, solid blue is 5V in and the two striped blue are tied together and are connected to ground.


Here's a shot of the voltage regulator. You can see the striped blue wire coming from the LM1881 to the center pin which is ground, along with another ground wire from the CXA1645, as well as the solid blue 5V wire from the LM1881, and the 5V line from the CXA1645 (Will show shortly) connected to voltage out, which should supply a 5V voltage to all components.


Here's the CXA1645 itself. Pin 1 is grounded, pins 2,3,&4 are RGB respectively, pin 5 is No Connection, pin 6 is connected to pin 3 of the oscillator (shown above the IC), pins 7, 12, & 19 are all tied together, and fed into pin 4 of the oscillator, which is connected to the voltage out on the regulator (shown in the previous pic). Pin 8 is no connection, pin 9 is grounded, and pin 10 is sync in. Pin 11 is no connection.


Bottom half of the 1645. Pin 13 is connected to a 47KOhm resistor and a 0.1uF capacitor, which are then each ran to ground. Pin 14 is connected to a 10uF capacitor connected to ground, while pins 15 and 16 are connected to a 75ohm resistor and a 220uF capacitor in series each, connected to chroma and luma respectively. Pin 17 has no connection. Pin 18 is connected to a 20kohm resistor out to ground. Pin 19 has been discussed earlier, pin 20 is also connected by a 75ohm resistor and 220uF capacitor in series out to composite out. Pins 21, 22, & 23 are not used for this circuit. Pin 24 is connected to ground.


Here's a shot of the ground wires all bundled together and fed into a single wire for organization's sake (note: my finger is on the composite out wire; the striped orange wire ABOVE my finger is connected to the bundle of wires running to ground:


So... here we are.

[thesteve]

check if the output from the 1881 chip will give a raster (sync no-pic) on your monitor.
another note when you have multiple grounds tie them together at the chip

[lastcallhall]

check if the output from the 1881 chip will give a raster (sync no-pic) on your monitor.
another note when you have multiple grounds tie them together at the chip

OK, I'll take a look shortly, thanks.
Also, I tied together several groups of ground @ the chip - there's something like 12 grounds on the unit and I got them down to four before tying them up to one on the way out...