Matchbox s-vid encoder

Ive just completed my matchbox PAL encoder project.





Has anyone made one smaller than this.

Reason for the project is mainly because I wanted to try the AD 724, my 725 encoder works well with mvs boards but is shit with most other boards. The 724 does not use a 4FSC clock (there is an option to do this if you wish), normally its a straight 4.43 MHz parallel-resonant xtal for PAL, it will be interesting to see if this has an effect on the colour with other boardsets issue. (Thanks for the chips John Smith )
AD do not ship to PNG for some reason

Read all about the 725 woes here:
http://www.neo-geo.com/forums/showthread.php?s=&threadid=74336&highlight=colour+encoder

I thought Id make a mini encoder just for fun, the challenge is on- who can build a smaller encoder.
I left the 3 x 75ohm RGB termination resistors out because my supergun has them wired to the jamma socket pins.
Also I havent bothered with comp video, the AD 724 does not use a luma trap, so the cross chrominance may be an issue. So its S-video only.
Could have left the variable cap out I guess, its just that after the chroma problems experienced with the 725 thought it would be good to have some adjustment here.
Looking forward to testing it tonight

Damn no chroma even with MVS. something obviously wrong with the wiring. Tomorrows another day.
Other boards seem to run better (in B/W) than with the 725

Edit: The sync is more stable. Raiden 2 boardset would continually vert roll with the 725 but locks with the 724.

Pretty good setup, but I'd expect part of your troubles are caused by the fact that you are cramming it in so tight an area. Probably getting some shorts in addition to the 724 vs 725 issues. What are the dimensions of your circuit?

Here's a board I just did with a CXA1645P. Next to a JROK 3.0 for size comparison. I could chop about another 0.5 to 0.75 inches off it too pretty easily. No shorting on this one.

The board is 18mm X 30mm (0.75" X 1.25")

There are no shorts, about 1mill clearance on each lead, I need to check the logic for pal/ntsc enable. May have got that wrong.

How do you find the colour using the CXA encoder on non mvs boardsets ?

ttooddddyy said:

The board is 18mm X 30mm (0.75" X 1.25")

There are no shorts, about 1mill clearance on each lead, I need to check the logic for pal/ntsc enable. May have got that wrong.

How do you find the colour using the CXA encoder on non mvs boardsets ?

Click to expand...

I actually use the CXA based encoder for Turbo Grafx/Duo and PC Engine mods for S-Video and it looks great! The colors are just right, which is normally a challenge on the Turbo systems since they have weak RGB output. The CXA1645 (and also the CXA1145) work well for just straight amplifying the RGB signals. I don't use if for composity since those systems have that already, but it should work fine if you hook up the luma trap. The nice thing about the CXA1645 is you can readily find the SMT version in Saturns and early PSX systems (also in a few Gen 2 Genesis and all Gen 3 Genesis systems).

But I've never tried the CXA chips on other arcade (or even MVS) setups, but it should work fine. The CXA chips are used in the AES systems and the 1645 specifically is used in the Neo CD.

Im just about to chuck it in with the AD encoders. The no chroma was due to the wrong capacitance accross the xtal (the VC was stuffed). Tried running the AD724 in both PAL & NTSC, same results= unstable sync, intermittent colour.

So Im resigned to the fact that the AD 724/725s are excellent for encoding comp/s-video from MVS and a few other jamma boardsets. But generally speaking the performance with most jamma boards is lousey using pal or ntsc, even when splitting and tailoring the sync input(s) to the encoder.

How do jroks look with various jamma boards. Must get one to find out I guess.

how are the jroks going with other boardsets ?

Toddy,

I'll let you know man. I buckled down and got a JROK after I burnt out a couple of the AD chips.

James said he mailed out my JROK soon so I should get it this week.

Oh, ToeJam, meant to get back to you too.

I'm still in the process of testing my encoder too. I tried it on a MAS 'gun and it was WAY too bright. Need to screw with the levels a bit before I release it for anything other than Turbo Grafx stuff.

D-Lite,

What kind of TV do you have for use of your MAS system? And do you have any of the Midway games like Ultimate Mortal Kombat 3 that you can try?

TV is a 32" RCA or Samsung, can't remember which. No Midway games though, sorry. And actually the MAS Systems Gun belongs to 300wins