complete DUO S-Video mod

[kid_rondeau]

Grahf,
I finally finished my S-video mod for my TG-CD, and it works...just not very well. The picture (color, clarity) is beautiful, but it's kind of wavy and jumpy. Any idea what this could be? I built the circuit per the diagram, and the only substitution I made was using the EL1881C for the LN1881 which I can't find.

[grahf]

I havn't tried the EL1881Cs yet personally, so unfortunatly I cant say. Its supposed to be a drop in replacement, so it SHOULD work fine.

Its hard to guess exactly what the problem is without seeing it in person.. It sounds like it could just be some interference. Double check the grounds, and also recheck the decoupling caps for VCC1 and 2 (make sure the polarity is correct on the electrolytic caps). Also, where are you getting your 5v from? If you look at the pic of my first board I posted on the first page, you can see that I pulled power from the middle of the board. There is a nice wide 5v plane which you can tap into.

Dont give up on it, you'll get it going eventually.

[kid_rondeau]

Whoa, thanks for the quick reply!

Here's an update:
I rechecked my connections and saw nothing flagrantly wrong, so just for the heck of it I tried the sync line on the expansion board in place of the stripped sync signal from the composite...YUCK!! It was dim and B/W and the vertical hold was off...I figured I'd have better luck if I went back to how I had it before, and retried.

I don't know what I did differently...maybe I just had a crappy connection from the 1881 before, but...

WOW!!!!

What an INCREDIBLE picture!! The first game I tried was Sidearms. No more weird "flashy" buildings in the first part of stage 1! And all the blues look so rich!

It is ALMOST completely stable as far as the picture is concerned. If you look VERY carefully, there is some periodic distortion about a third of the way up every few seconds. It's so minor, though, that I scarcely even notice...and I'm VERY picky about stuff like that.

Thanks for the encouragement!

[nat]

If you look VERY carefully, there is some periodic distortion about a third of the way up every few seconds.

Those are my Dark Lord powers affecting the planet's magnetic field. Don't worry about it.

[D-Lite]

The LM1881 is readily available in any quantity from Jameco if anyone needs them.  Both SOIC ($2.34 each) and DIP ($2.85 each).

[kid_rondeau]

OK! Got it!
I wasn't satisfied with the distortion on the picture (however minute) so I did some circuit cleanup last night, including:

-I didn't bus all the ground connections together
-I brought the 1881 about 1cm closer to the 1645
-I didn't use a socket for the 1881 (not sure if this helped, but you never know)

After about three hours of work, I tested it, and it works completely perfect now. Huzzah!

[grahf]

Nice work man, congrats on the finished board. Its a great feeling when you finally get something working.

[nat]

Anyone know where I can get a cxa1645m? I see I can get the LM1881 from Jameco.

I don't want to order a bulk quantity of the CXA's, just 1 or 2.

So I guess if any member here has a couple extra they want to sell me...  :-"

[Michael Helgeson]

If yo don't have a local source check ebay. They get sold off and on there.

[nat]

There's one listing up right now. The seller has 135 of these chips, but he's asking $20 a pop plus $8 shipping. Needless to say, shipping something the size of a quarter domestically doesn't even come close to $8. Beyond the obvious raping on the shipping charge, $20 seems a bit high to me.

Or is this what I should be expecting to pay for this item?

[Michael Helgeson]

Currently,yea,unless you have a local supplier that will let you pay slightly more then what they get them at in bulk.

You can also strip the chip off of dead Saturns and I think Ps 1 systems use them also.

[D-Lite]

There's one listing up right now. The seller has 135 of these chips, but he's asking $20 a pop plus $8 shipping. Needless to say, shipping something the size of a quarter domestically doesn't even come close to $8. Beyond the obvious raping on the shipping charge, $20 seems a bit high to me.

Or is this what I should be expecting to pay for this item?

That's about the going rate.  Unless you feel like buying 100 of them

[nat]

I bought everything else that I need to do this mod today.

I guess I'll go ahead and order a couple of those from that eBay seller.

I'm going to go ahead and build an encoder based on grahf's work early in the thread. I'm going to do the mod first on a core TG-16 and see how it goes. I might try my Duo next if all goes well.

[CkRtech]

Odd place for my first post, but -

I just bought into the TG16 world for the first time this week. The original U.S. TG16 should arrive any day now. It's pretty exciting. I have never owned a TG16 OR played a TG16. I remember the commercials for it - going to Babbage's and seeing it out on display. Never played it.

That day will come to an end soon as it gets added to the collection of game consoles and games. One thing I make a hobby is improving video output of VG consoles. I'm not a guru in the area at all - I just have an interest in it.

nat - I would like to hear about your experience modding the core TG-16. I have an external RGB -> S-Video solution for the Sega Genesis, and I wouldn't mind rigging up a cable on the TG-16 that allows it to use the Genesis adapter. I am not sure if the level of RGB output is the same for the TG16 compared to the Genesis or not. If so, it should be an easy mod.

Look forward to talking TG video output with you guys,
CK

[nat]

I haven't done much with regards to video on the Genesis, but I can tell you that if you're looking to do an external "mod" on the TG-16, there is an expansion port on the back where you can tap the video signal directly off the VDC. You can get both RGB and composite from this port. I am assuming you are tapping the RGB signal from the Genesis in a similar manner, so your method would probably work on the TG-16 too.

The mod that I am doing is internal-- I'm actually going to add an S-Video port to the machine itself. Ideally, I'd like to do a component video mod but I understand that would be a bit more difficult.

Anyway, here is the pinout for the rear expansion port:

AR GG 01 VM 32 30 27 GG 17 20 22 23 13 11 10 08 GG 05 03 GG VV VN VR

02 CD 35 34 VU 29 26 15 19 21 VJ 14 12 VG 09 07 06 04 24 VT 37 36 VP

AL VV VS 33 31 28 25 16 VL VK QQ VI VH QQ VF VE VD VC VB VA GG VZ VQ


The pins you'd be interested in are:

VR -- Blue RGB signal
VP -- Green RGB signal
VQ -- Red RGB signal
VN -- Horizontal sync signal
VZ -- Vertical sync/composite video feed
AR -- Audio Right
AL -- Audio Left

All "GG" pins are ground.

I've personally never done anything with an RGB signal from one of these machines, but I have rigged up a few connectors over the years so I could use standard A/V cables for stereo sound and composite video on a core system that only has RF out of the box. Since I absolutely refuse to touch RF.