Sega Mega CD Pro CDX v1.80i problem and solution...

Had another look at my faulty Datel Pro CDX import player cartridge for Mega CD. The thing only worked every once in a blue moon. So I opened it up and replaced all the parts that could cause trouble. Being one capacitor and one mosfet. Also cleaned the pin connector thoroughly. To no avail. Still, I managed to find out what the problem was. Apparently the thing is very sensitive to residual energy. Every time I used the cartridge I have to unplug the power brick with the cartridge still in the console, and move the Mega Drive power switch on and off for a second to release any residual energy. After that I plug it back in, and it works like a charm every time. The more you know...

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Originally Posted by elmagicochrisg

Apparently the thing is very sensitive to residual energy. Every time I used the cartridge I have to unplug the power brick with the cartridge still in the console, and move the Mega Drive power switch on and off for a second to release any residual energy. After that I plug it back in, and it works like a charm every time. The more you know...

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How did your mind go there to think of that as a possible solution? But cool that you did. http://i.imgur.com/v99tEAu.gif

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Originally Posted by elmagicochrisg

Had another look at my faulty Datel Pro CDX import player cartridge for Mega CD. The thing only worked every once in a blue moon. So I opened it up and replaced all the parts that could cause trouble. Being one capacitor and one mosfet. Also cleaned the pin connector thoroughly. To no avail. Still, I managed to find out what the problem was. Apparently the thing is very sensitive to residual energy. Every time I used the cartridge I have to unplug the power brick with the cartridge still in the console, and move the Mega Drive power switch on and off for a second to release any residual energy. After that I plug it back in, and it works like a charm every time. The more you know...

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Wait, there's a MOSFET in there? that's really hard to believe...do you have a pic? I'm always intrigued at the guts of Datel products.

I know you have to switch a NES and SNES on and off after disconnecting it before you mod it. To get rid of the stored energy on the board. That's why you can still see the red light come on for a split second after you unplugged it and you switch it back on afterwards. So with that thought in mind, I tried getting rid of any residual energy that might've stored up in the cartridge...

Also, I'm persistent... lol

Mosfet: ZVP2106A

Attachment 10557

It's not broken, sir. Mine does the same thing. The cure is find yourself a non TMSS Mega Drive unit. The problem is the design of the CDX "anti TMSS" circuit. It doesn't work very well and causes the damn cart to fail booting often.

Honestly get yourself a region free BIOS and toss the CDX PRO back to the drawer (it's a nice collector item but not really that useful considering that a few games try to detect it and then refuse to play).

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Originally Posted by segasonicfan

Wait, there's a MOSFET in there? that's really hard to believe...do you have a pic? I'm always intrigued at the guts of Datel products.

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The point of that transistor is allow the cart to control the /CART pin. For that to work, there's the DATEL PAR ASIC (so it can apply cheat codes into the CD BIOS to mod it's behavior), the CDX ROM with the patches and the splash screen program and a PAL (programmable logic chip) which in turn control the said transistor. The PAL is there to disconnect the CDX ROM and set the /CART pin high so the CD BIOS can boot with the PAR ASIC already set up with the cheat codes which modify the CD BIOS for REGION FREE.

The reason why the OP has that problem is that the CDX cart has a circuit to bypass the TMSS screen and it depends on the charge/discharge of a electrolytic capacitor which is on the CDX board exactly to control the TMSS bypass circuit state on power on.

On a non TMSS console that is not necessary and has no effect on the boot process so, 100% boot rate, no weird rituals with the cartridge or with the cables. (lol)

Wow, thanks for the thorough explanation. At least now I know there is 'nothing wrong' with my cartridge...

Just wish I had known that sooner. Oh well, a fresh cap never hurts... :lol:

I also have a Mega Everdrive, so I can load any BIOS I want. Still, I like using the Pro CDX and don't mind the workaround.

Something about using old hardware just feels more satisfying... :stick:

Everdrive doesn't work properly for loading the CD BIOS. Horizontal VDP interrupt doesn't work properly due to that.


A couple big games including Snatcher and Silpheed fail to run or glitch while running the CD BIOS from an Everdrive because they use/require the horizontal interrupt feature...