Where to get: Sony CXA1645 chips

[PDP-13]

Whats the video quality like on the Analog devices 725/724 ?

At their side they list it as a very 'economical' component, which is synonymous in my mind with cheap and junky.

Or is it good?

[PDP-13]

Also a circuit diagram would be nice.
(NTSC, Composite synch, with no luma tap as I'm using Svideo...)

[Guest_viletim]

PDP-13,

Download the datasheet and see the app. circuit "Interfacing the AD72x to the (Interlaced) VGA Port of a PC".

The AD725 requires an oscillator (also in the datasheet) and you can leave off the Y-trap componets if you like.  If you're using an AD724 you can connect it straight to a crystal without the needs for ans osc. circuit.

I've not personaly seen the output of one of these chips so I can't comment on the quality (i'd expect it to be pretty good though).

[D-Lite]

The AD chips are different and I don't just mean the look and layout.  They perform significantly differently than the Sony CXA chips.  I use an encoder that has the AD724 and another that has the AD725 and they don't work with a lot of systems that the CXA does.  It really depends what you need it for.  The AD chips work great with Neo Geo, Atomiswave, and a few others.  They do work with Turbo Grafx and Genesis, but some effort is needed to get them to work.

[PDP-13]

Really... Hmmm.

well I've given up on the Sony chip... its costly and uncommon.

How tricky can it be?

If I've got a 15Khz RGB and Composite synch input of any sort (in the proper .7 volt range) this chip should be able to handle it right?

(Genesis[32X/CD] / Neo Geo / TGFX-16 / Ect...)

give or take a few capacitors or resistors. Also you can't beat the price. (Free!?!  :lol: )

[phreak97]

i could sell you a CXA1645M out of a correct model psx which went to parts long ago if you wanted. even though it's international shipping it should be cheap.

[RARusk]

"The one problem I have with RGB -> S-Video converters are;
They are bloody expensive.
$100 or more (usuall MUCH more.)
I have a schematic for a Sony CXA1645 RGBS to S-Video/composite converter, but!
I can't find a single source for Sony CXA1645 chips in North America (so far).
I don't think the whole thing would cost more than $45, including connectors and other fiddly bits (which are easily found).
Does anyone have some of these chips, or know where to get them?
any help would be much appreciated."

Maybe you might want to take a gander at this:

http://www.neobitz.com/Pages/Mods/SystemMods.aspx

I don't know the price but it should be inexpensive plus you get Component Video as a bonus. It might also work with Progressive Scan RGB (VGA) - think DreamCast. Imagine playing "Soul Caliber" on a large Progressive Scan capable Component Video TV.

[Endymion]

Still can't find one? What about a Sega Saturn? Don't all Saturns have the 1645? Find a broken one and go to town. Some guy on ebay was selling bundles of them last year--yeah, broken!

[phreak97]

well, i'd send anyone a cxa1645 for like $10 inc postage... i have only one though

[PDP-13]

To RARusk; yeah its $100+ US. (no single boards sell for less than $100 and I suspect they use the SAME chip I am.)

To Endymion; sacrifice a PS I might, a Saturn NEVER!  (well perhaps a broken one)


Also even if the Analog Devices AD 725 I have sucks hugely, it did not cost me.

Too bad those Tiny little pins are going to be uber tricky to solder...

(I'm going to hand solder a thin copper wire to each pin, and that wire will go to a wire wrap board of some kind.)

not a ideal solution but it should work.

If I had a digital camera I would take some pics and make a little guide for those who want to build the same... oh well.

[phreak97]

dont use bare copper wire, it oxidizes, itll turn into a resistor eventually. use wire wrapping wire, the stuff i got is some mix of copper and some other coating, itll never oxidize, it's made to be exposed. i soldered bits of it to each pin on a smaller chip with the same pin spacing, then put the wires through a bit of perf board with enough space to not short anywhere. it works perfect.
if you want a pic, let me know, you can all see my crappy job of soldering this one.

[werejag]

can someone make a pcb layout for AD 725 for a neogeo

[laugh]

For any of you wondering how to solder the SOP CXA1645M IC onto a breadboard of any sort, check this little piece of board out.

My RGB -> NTSC converter pics

That little piece of board will let you mount a SOP IC and then attach onto regular DIY boards' holes.

I took apart a broken Saturn, and snatched a CXA1645M and  2 VHC04 IC's. I used VHC04 in my circuit instead of HCT04 or HC04, because it's just plain BETTER in every aspect, plus 2 of them were in the Saturn for free.

I found it pretty easily, but I'm in korea. You should try to look for these to mount the CXA1645M as well as the subcarrier generator IC (Hex inverter, ie. VHC04), it's no sweat and neat as well.

I wish I knew that I could post as a guest a little sooner.

[werejag]

can you go into more detail so i can build one?

im ntsc since im in the states

[PDP-13]

Where did that SOIC adaptor come from... that would be much better than soldering transformer core wire to each pin. (and getting half the connections either shorted or cold-jointed...  )


Also get these PDFs from the Analog Devices site:
120333814AD725eb.pdf
774020909AD725_0.pdf

The evaluation board gives out the whole circuit, but the documents are not that easy to read... <_<  

[phreak97]

if youre going to solder wires, like i did, dont use transformer core.. it's insulated, and you cant strip it easily.. it's a bitch to work with. use 'wire wrapping wire' and strip the insulation off the whole strand if you need to. it's plenty thin enough for the rgb encoders, and it has an alloy coating so it wont corrode. while yes, it isnt designe for soldering, it solders 100% fine, it's what people use in ps2 mods alot of the time. it's perfect for almost any console mod, it's single strand, no stray bits, it's made so when you bend it into place, it stays there, it's uber thin, and itll take an amp through it quite happily (my tests show it starts getting warm about 1.6A at around 12v or something, it burned the insulation at over 2A). this all means it's perfectly fine for led mods, region switches, anything really. also the insulation doesnt shrink back more than half a mm or so, so it's great for tiny joints where you only want a fraction of a mm stripped off the end.

heres a pic:
wire

[viletim!]

yup...wire wrapping wire is the stuff to use. It's only rated for about 300mA so don't use it when real current is involved.

[werejag]

anyone good at making pcbs
can someone design a pcb for either the ad725 or the CXA1645 chips

[emuman100]

The CXA2075 is a great IC, but when in use it gets HOT! There is a CXA2075 in the TV de Advance. The video quality is excellent, but noisy in the TV de Advance because it's a cheap device made in China.

I plan on using either the AD725 or the CXA2075 with my project that includes an ADV7125 video DAC. Probably the AD725 will work best with the AD DAC and produce nice video, but I'm not even sure yet. I'm building a circuit that takes the LCD signals from the DS and converts them into NTSC signals. This is hard enough as it is without worring about what RGB encoder to use.

[RGB32E]

I have an AD725 Evaluation board.  Unfortunately this device (as an eval board) is not compatible with many arcade PCBs.  The Capcom CPS1 and 2 based games look awesome... provided that you have about 300 ohms series resistence on R, G, B video signals (to drop the voltage).  I haven't tried my Neo-Geo MVS... partially because the free board I picked up doesn't boot properly!

One thing to note about the AD725 is that it can accept both separate and composite syncs.

[Guest]

A fair warning to all you PSX vandals: I gutted SCPH-7501 for spares (needed laser unit for blude debug anyway). Unfortunately there is no CXA1645 chip in this model.