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 The CXA2075 AV Famicom

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Drakon
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PostSubject: The CXA2075 AV Famicom   Wed Feb 08, 2012 11:10 pm

Today I soldered together the video circuit of one of the kits I ordered. I wanted to test if it's possible to replace the cxa1645 that comes with the kit with a cxa2075 so I didn't solder in the encoder chip. Since I just wanted to test if the chips would be compatible I wired up the cxa2075 in such a way that it would easily be removable. So I present you with......

The cxa2075 av famicom prototype:



And does it work?



Better than I expected! Now I'm going to clean up my gaming area and test to see if the video quality looks improved over the cxa1645. There's also a chance that the picture quality will be even more improved with the encoder soldered right onto the kit but I ran out of loose cxa2075 chips and I'm waiting on the next batch to show up.
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PostSubject: Re: The CXA2075 AV Famicom   Wed Feb 08, 2012 11:12 pm

Did some testing and indeed the picture is sharper than before! Also I think the colour encoding looks a little better than before! I ordered some more loose cxa2075 encoder chips a while ago so I'll wait for those to show up before I solder one directly onto the kit pcb.


Last edited by Drakon on Wed Feb 08, 2012 11:28 pm; edited 1 time in total
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teknix1



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PostSubject: Re: The CXA2075 AV Famicom   Thu Feb 09, 2012 6:07 pm

Nice work Drakon! I'll be ordering the chip to replace the 1645 in my kit. Was it a simple drop in replacement or did you have to change the circuit surrounding it a little?
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PostSubject: Re: The CXA2075 AV Famicom   Thu Feb 09, 2012 6:37 pm

teknix1 wrote:
Nice work Drakon! I'll be ordering the chip to replace the 1645 in my kit. Was it a simple drop in replacement or did you have to change the circuit surrounding it a little?

It's almost a drop in replacement. The composite video circuit is different and I havn't messed around with wiring that yet.
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PostSubject: Re: The CXA2075 AV Famicom   Fri Feb 10, 2012 1:05 am

CXA1645:



CXA2075:

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teknix1



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PostSubject: Re: The CXA2075 AV Famicom   Fri Feb 10, 2012 1:09 am

Nice work! Seems like there's a slight change in brightness or contrast. Regardless, I'm very anxious to see where you can get from here by playing with the circuit.
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PostSubject: Re: The CXA2075 AV Famicom   Fri Feb 10, 2012 1:36 am

teknix1 wrote:
Nice work! Seems like there's a slight change in brightness or contrast. Regardless, I'm very anxious to see where you can get from here by playing with the circuit.

Yeah the 2075 kit I weakened the resistor because the s-video from these kits looks a bit dark. Really there's nothing to "play with" at this point it's as good as it will ever get right now.
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teknix1



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PostSubject: Re: The CXA2075 AV Famicom   Wed Feb 15, 2012 6:41 pm

This is awesome, any chance you might share the specifics of this mod? What value of resistor, etc... I got my board yesterday. Still waiting on the CXA2075, should be a matter of days now.

Thanks in advance!
Nic
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PostSubject: Re: The CXA2075 AV Famicom   Wed Feb 15, 2012 6:44 pm

teknix1 wrote:
This is awesome, any chance you might share the specifics of this mod? What value of resistor, etc... I got my board yesterday. Still waiting on the CXA2075, should be a matter of days now.

Thanks in advance!
Nic

Uhh I already have extra cxa2075 chips you didn't need to order any. Anyway the av famicom kits I use are designed for the cxa1645. The cxa2075 is meant to be a pin compatible drop in replacement for the cxa1645 which it is. I only changed one part from a cap to a resistor but even that part's only necessary for composite video. Anyway just check the datasheets for the cxa2075 and the 1645 and you'll see for yourself.
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teknix1



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PostSubject: Re: The CXA2075 AV Famicom   Wed Feb 15, 2012 7:14 pm

Sounds good, I'll take a peek at the datasheets then.

Thanks
Nic
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PostSubject: Re: The CXA2075 AV Famicom   Sun Feb 19, 2012 12:24 pm

After extensive testing this mod is a complete success and 100% finished. The only thing my cxa2075 video circuit lacks is composite video but I don't care at all about composite video so I consider this mod as completed.
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