I killed my Mega-CD when I tried to install a region-free BIOS

I fumbled big time.

Hi guys. I ordered a Mega CD 2 BIOS to Bad_Ad84 and for some reason the installation went wrong. Long story short I failed at desoldering the chip, tried to cut the legs, failed again, then successfully used braid to desolder it. I then put the chip on a socket, soldered it, then got a black screen, no led. I'm usually not bad with a soldering iron but obviously that was an off day for me.

I suspect I messed up the board when I tried to cut the legs. Then again maybe my soldering is just off. However I have no idea how to test each leg, as I can't follow the traces and I don't know where they are going. My question to you is: where do each pin go? More specifically where do pin 19 and 20 go? These two are the ones I tried to cut and messed up most. If the trace is fucked up, at least I could try to run a wire to where it should go to repair it.


tl:dr; Where do each BIOS pin go?

 

Do you have a multimeter? You need to test continuity with all connections.
Did you actually put the chip in the socket before soldering the socket?
To clear some confusion, what chip is now in the socket, the old chip or the new one?

 

I would imagine the service manuals would have the information.

 

I do have a multimeter.
I did put the chip in the socket before soldering it. Is it bad?
The new chip, the programmed eprom, is in the socket. I have destroyed the original BIOS chip in the process, several legs are broken.

It probably would! I will look at them now, I didn't know they were online (and on this forum, no less!)

 

Does it have continuity beeper? If so use it. First check connection between each chip leg and the socket legs. Then follow the traces going from the socket legs until you have a point you can probe and test continuity. I do not think anyone is going to draw you a picture of it, you will have to follow the traces yourself, or look into the service manuals.

Well, sort of. Normally you install the socket, then put the chip in. It avoids unnecessary stress on the chip. IT also solders better as you have less mass to heat.
Talking about the new chip, you inserted it on the right orientation?

The beauty of removing chips without damage is that you can then reuse it for troubleshooting purposes. No use discussing that anymore here.
Maybe you can post a picture of the area of the board you worked on?

 

That's the thing though. Because the Mega-CD board is multi-layered, several traces run within it and can't be followed. I found the service manual here http://www.assemblergames.com/forums/showthread.php?44343-Sega-Service-Manuals with the BIOS pinout and the connections. I'll check them as soon as possible.

Yep, I checked that several times. I may redo the solders on contentious pins without the chip in, once they're identified.

I know! I was really upset when I realised (wrongly) that I couldn't desolder it and that I had to cut it. Then after I tried to desolder it again I felt how I wasted a chip.


I found the service manual here http://www.assemblergames.com/forums/showthread.php?44343-Sega-Service-Manuals with the BIOS pinout and the connections. I'll check them as soon as possible.

 

Moved to the modding forum - the Sega forum is really for development. You should get more help here.

The answer is that you're just going to have to sit and work out what you did wrong for yourself. A decent light, a magnifying glass (a magnifying light is a good option) and a multimeter will be your friends here.

 

oops, sorry I didn't see that section.

Yes, I know I'll have to work it out myself. But you guys giving me the service manual was already a huge help.

 

The most likely problem might be that you broke a trace just next to one of the pin, or also very likely you ripped off one side ( or both ) of some of the through-holes pads. Try removing the chip, it might help you see better then check visually the condition of each holes and the surrounding traces.

I have never working inside a sega cd yet but I know that those pads are very fragile on some genesis.