Neo Geo AES NTSC refresh rate

C

Cyberdemon

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Hi,
I want to know if its possible to modify a NTSC AES to output a signal in 59.94 Hz and not the non-standard refresh rate 59.1856 Hz that the Neo have.
I must change the crystal oscillator from color carrier to get the standard NTSC refresh rate (59.94 Hz)?:conf:
I will apreciate so much your help.:)

P.S. Sorry for my bad English
 
N

NEO-GEO man

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Is it just me or.....

Scanrate3.jpg


MVS was the same too.
 
Xian Xi

Xian Xi

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61.18hz is on the newer AES systems 3-3 to 3-6, 1st and 2nd gen are 59.18hz. This was changed with a different crystal. 1st and 2nd have a 24mhz crystal and the newers are 24.16mhz.

MVS should have the 24mhz so it's weird if you're saying MVS is the same.
 
shadowkn55

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Would it be possible to fudge some of the numbers during horizontal scan with a re-written bios? There are a few pixels on the non-active video portion that could be removed to bring the refresh rate closer to 59.94hz.
 
C

Cyberdemon

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shadowkn55 said:
Would it be possible to fudge some of the numbers during horizontal scan with a re-written bios? There are a few pixels on the non-active video portion that could be removed to bring the refresh rate closer to 59.94hz.
Click to expand...

Maybe Razoola can answer these question, because he is the master of the neo-geo BIOS...(I have UNIBIOS v3.0 in my AES)
 
N

NEO-GEO man

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Xian Xi said:
61.18hz is on the newer AES systems 3-3 to 3-6, 1st and 2nd gen are 59.18hz. This was changed with a different crystal. 1st and 2nd have a 24mhz crystal and the newers are 24.16mhz.

MVS should have the 24mhz so it's weird if you're saying MVS is the same.
Click to expand...
Tis a very new model of MV-4 FT, so maybe it is holding the same XTAL as well. I will have to try the really old 2 and 4 slotters i have here and see what they say.
shadowkn55 said:
Would it be possible to fudge some of the numbers during horizontal scan with a re-written bios? There are a few pixels on the non-active video portion that could be removed to bring the refresh rate closer to 59.94hz.
Click to expand...

No. Doesnt work that way. BIOS has nothing to do with it dirrectly.
 
C

Cyberdemon

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Nobody knows about it? I will try to change the crystal of 24.00 Mhz by another value between 24.00 and 24.16 Mhz to reach the 59.94 Hz of refresh rate and then i will see what happen...
 
N

NEO-GEO man

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Give it a go, if it doesnt work, put the original back in!! ;)
 
mjs256

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Cyberdemon said:
Hi,
I want to know if its possible to modify a NTSC AES to output a signal in 59.94 Hz and not the non-standard refresh rate 59.1856 Hz that the Neo have.
I must change the crystal oscillator from color carrier to get the standard NTSC refresh rate (59.94 Hz)?:conf:
I will apreciate so much your help.:)

P.S. Sorry for my bad English
Click to expand...

There should be a coupling capacitor next to the crystal - changing the capacitance should slightly alter the frequency. Some boards have an adjustment screw to make it easy to adjust. Otherwise you can just put in a new capacitor with a different value.
 
Xian Xi

Xian Xi

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Make sure you change the right crystal and not the clock for the encoder. On the 3-3 to 3-6 it is in the lower right corner of the board.
 
GMFattay

GMFattay

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Cyberdemon said:
Nobody knows about it? I will try to change the crystal of 24.00 Mhz by another value between 24.00 and 24.16 Mhz to reach the 59.94 Hz of refresh rate and then i will see what happen...
Click to expand...

Did it work? Would love to do this mod to my MVS to try to get it working on my LCD
 
C

Cyberdemon

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GMFattay said:
Did it work? Would love to do this mod to my MVS to try to get it working on my LCD
Click to expand...

I could never get a crystal with values ​​between 24.0 and 24.3 to test ... but as soon as I try and get some discuss here how it works.
 
Tengugurl

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Does anyone know how to install a 24mhz Crystal into a first version AES?
 
Xian Xi

Xian Xi

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Tengugurl said:
Does anyone know how to install a 24mhz Crystal into a first version AES?
Click to expand...
Is yours missing? It’s on the upper left middle of the board but if you have the daughterboard it’ll be there instead.
 
Neo Alec

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I swapped out the 24.16 crystal for a 24mhz crystal on my 3-4 board. The readout on the OSSC went from 15.72kHz, 59.79Hz to 15.61kHz, 59.37Hz. It's close to my MV-1C, but not quite. The MV-1C is 15.62kHz, 59.18Hz. Moving the nearby pot doesn't appear to make any difference. Is it a problem if I have that pot set wrong?

I'm also curious why the AES always shows 263p , while the MV-1C says 264p. The AES is RGB bypassed, using the attenuated TTL sync.

Edit: Also, there is now more noise in the image on the Framemeister too. I guess the Framemeister is more sensitive about the refresh rate than I thought.
 
Last edited:
Neo Alec

Neo Alec

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Well, I learned something today.

First I reverted my AES by putting back the 24.16 crystal. The video looks clean again on the upscalers.

So then I decided to take an extra 24.16 crystal I have from a parts system, and put that on my MV-1C. With this change, the OSSC now reads 264p, 15.73kHz, 59.59Hz (not quite the same as the refresh on my AES, but pretty close). This has fixed most of the video noise I've been dealing with on that system for years, and removed the need for extra capacitors on the R,G and B lines. It's still slightly noisier than the AES, but a huge improvement. Very useable, and no longer needs weird brightness settings to look nice.

I wonder why more people haven't mentioned the refresh rate issue in regard to brightness and noisy picture. My MV-1C has the Tianfeng AV board installed, and it still didn't look right until I did this. Maybe because the refresh is better or worse on certain boards?
 
M

maki

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Neo Alec said:
Maybe because the refresh is better or worse on certain boards?
Click to expand...
When I compared the first gen chipset and the composite sync/ horizontal-/vertical blanking (SYNC/CHBL/BNKB) the different LSPCA revisions create, it was very obvious that all the syncs are very dirty coming from the LSPC-A0, the LSPC2-A2 is much cleaner and also has some extra concrete blocking/filtering caps.
I don't have a working MVS with your chipset on it (MV1C uses the last/latest IIRC) to check that.

Some DFO solutions aim for 24.3ish MHz instead of the AES 24.168ish to increase the hor. sync frequency and have better compatibility with LCD TVs.

I haven't noticed any other picture improvements on the first gen boards with different crystal speeds, but currently only running a CRT, no OSSC/HDMI, and didn't pay attention to that tbh.
 
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