Problems modding Saturn VA13 from PAL-M to NTSC

[robmanv]

Hi guys, i´m trying to mod my sega saturn VA13 from PAL-M to NTSC (below some pictures of original situation). I just swap a crystal oscilator (X1) 14.302 mhz to 14.318 and it stop´s from read any cd-r or originals (shows like a music cd).

What i did that shows a perfect NTSC image but dont read any games (shows like audio cd):
- Link IC21, point 1 and 7.
- Removed JP2 link and put it on JP1.
- Put a 2k2 resistor on R142 (near IC21), without it the image appeared missing colors.
- Swap cristal oscilator 14.302 for 14.318


I realized that just swapping the cristal oscilator from 14.302 to 14.318 is enough to make my saturn stop reading disks. When i put back the crystal 14.302, with same soldering showed in pics below, my saturn go back to normal playing any games but in pal-m mode.

[zyrobs]

Does it struggle reading the disc or does it instantly checks them as audio? Can you hear it moving up to check the security ring?

Might just be the laser needing a tweak.

[robmanv]

Instantly check as audio. When i put another regions cd-r, show that the cd is incompatible.

[buckoa51]

Interesting results. Hey Zyrobs have you ever done a successful crystal swap or know anyone who has on a Saturn? This is something that I was intending to look into at some point so I am curious.

[robmanv]

I think that after swapping crystal oscilator creates some clock disparity. Everything appears perfect without reading any disks. Maybe linking R142 resistor is not a good option.

[zyrobs]

Mar 20, 2015 9:56:23 GMT buckoa51 said:

Interesting results. Hey Zyrobs have you ever done a successful crystal swap or know anyone who has on a Saturn? This is something that I was intending to look into at some point so I am curious.

I've fully converted one of my PAL Saturns to a NTSC unit (swapped the master clock from 17-something Mhz to 14.318Mhz), and I recall SaturnHST doing something with one of his units as well.

Mar 20, 2015 15:02:44 GMT robmanv said:

I think that after swapping crystal oscilator creates some clock disparity. Everything appears perfect without reading any disks. Maybe linking R142 resistor is not a good option.

R142 is bridged with a 0ohm resistor on a factory ntsc va13 unit, so bridging it is not a problem. All the changes you made correspond to differences between the Brazilian PAL-M units and factory NTSC units, so as far as I know it should work. Such a small clock speed difference really should not affect the unit, if it did they'd have used an extra crystaé for PAL-M compatibility, such as with the tectoy skeletons (which are stock ntsc but have an extra oscillator board next to the video encoder to output the necessary clocks).

I just noticed that you have a modchip there. Have you tried loading games without it? Also, can you post some pictures of that chip, front and back?

[buckoa51]

I've fully converted one of my PAL Saturns to a NTSC unit (swapped the master clock from 17-something Mhz to 14.318Mz), and I recall SaturnHST doing something with one of his units as well.

Nice, I'm looking into getting a dual frequency oscillator to market, so I might have further questions for you.

[robmanv]

Yes i tried without modchip and had the same results, reading as audio cd. Here is some pics of modchip:

[zyrobs]

Excuse the 2 year bump, but a friend had the same problem, and pointed out to me that the CD Block ASIC uses a different crystal. Normally all Saturns use 20MHz, but on the VA13 Tectoy PAL-M units, they use a 19.978MHz crystal.

20 / 19,978 = 0,9989

compared to the pal-m*4 master clock to the ntsc*4 one:

14,302445 / 14,318 = 0,9989

Both crystals were reduced by the exact same ratio. So at a guess, the reason why a VA13 Tectoy PAL-M Saturn ends up not reading the disc, after being modded back to NTSC, is because the CD Block is now running out of sync.

So, in case anybody else attempts changing a PAL-M VA13 units to fully NTSC: on top of replacing X1 to a 14,318MHz crystal, you also need to replace X5 with a 20MHz one. It's the crystal around IC37, near the battery in the corner.

[robmanv]

After 2 years i was hoping for this answer and i can say, it worked on the first try!!! Thanks my friend zyrobs, this answer is worth gold! Now i will enjoy my NTSC Sega Saturn.