MegaCD under the knife, surgeon's opinion needed

Years ago, I buy one Jap Mega CD very first run.
After months of good service, one night, I yelled very loud. (like in the movies you know, with arms in the air and stuff...)
I messed up with PSU and had fried my so beautiful Mega CD.

Black screen, no sound, no light, no disc turning...

Years later, i goes to a TV repairman with the AC board.
He test everything on it and fix them, except chip I guess.
Return to house, test: OMG screen of the sky!



But thats all, no sound and nothing more.
I said to myself: ok I try I lose.
I think the bios eprom may have been damaged.

Nowadays, Everdrive and Region Free Mega CD Bios make me mad!
Everdrive is mine but my Mega CD is still between life and death, and I need your help here.

I talked a little bit of my problem in the Mega-CD real region free thread and move it here, better place to bring back to life.

Some said that the problem was either from the transfer board, either from the flat cable between bios board and CD-Rom drive board.
After a real and deep inspection, I discovered that the inside of the machine was dirty as possible and bios board seemed to have some rust on it.


Situation:

If you prefer, here is the archive of all pictures below: Download.

• Transfer board

Seem clean.

• CD-Rom drive board

Seem clean too; dont want to dissect it.

• AC Board

Very dirty at some area but seem good.
On the 6th picture, it has a hit but continuity is good.

• Bios board

Here are coming problems...and a lot.
As you can see, some points seems unsoldered.
They are very, very small, and if my guess is right, work will be hard, very hard. :banghead:

What do you think about it?

• Bios Socket

Seem good.

• Bios Eprom

Written on it:
MBM27C1024-15Z
9147 R63

So here we are, maybe a rusty bios Board.
I try different Megadrive and it's always the same:
Power on, and after 1 second, sky appear but nothing more, no sound, no in front light, no turning disc.

What do you think about it?

 

Try with a new AC board, its the first thing that you have to do after an PSU accident ;D

 

I should have explain more on this point.
When I went to TV repairman, he took the AC board and fixed it.
He checked everything on it except the chip I think.
It is with the fixed AC board that sky screen reappeared.

And I would like to try with another AC board, but only got one Jap MegaCD.

I edit my first post for the explanation.

 

Electrolytic capacitors leaked, main processor board is corroded.

My MEGA-CD is exactly identical to yours but my board came with BIOS EPR-14563H.

EPROM is 27C1024 (16 bit, 128KB).:thumbsup:

You need to replace all capacitors on main processor board (what you're calling BIOS board) and repair all traces damaged by leaked fluid from capacitors.

My hacked BIOS should work fine once the board is repaired. Good luck ! :thumbsup:

 

Thanks for your answer.

Replacing capacitors should be alright.
About the trace, it will be very hard I think.
Traces are micro size and more, they are under a layer of a dark green kind of plastic.
By example in the middle of this pictures:



Here are size comparative pics:




The last one show the soldering iron I use to mod Megadrive or output RGB form mu Duo RX.
To be totally honest, I checked again the board and don't know if it's even possible.
My will on this titanic job very depend on one question as the board is corroded:
Will the rust expand very slowly to the rest of the board, even if I fix trace and capacitors?

 

It's not rust, its electrolyte. In all likelyhood its probably done doing its damage but cleaning it off the board is always a good idea regardless.

Replacing the capacitors is easy if you've got an iron with a smaller tip than that as well as the skill to not lift any traces in the process. Fixing the traces shouldn't be too difficult either if you've had experience doing so. After you lift enough like I have you get forced to learn how.

 

First thing is get rid of the corrosion source:

Remove all the bad capacitors (make sure you write down their values and positions)

WASH THE BOARD WITH NEUTRAL SOAP !

Leaving the board a few hours immersed in little bit of vinegar diluted in water is a good idea to neutralize the caustic from the rust after washing.

After the vinegar treatment, wash it again with soap and to finish, dry it with a hairdrier on mid power. :thumbsup:

The only parts of the machine you cannot wash that way is the mechanism/laser parts.

And remember, never try to power it on if it's moist/humid ! :-0

Actually water and soap is the best stuff to clean electronics.

 

Thanks for all those advices, I'll try it out but it's gonna be very difficult for traces.
I definitively can't let this first run MegaCD down. OH:

 

Don't say that. People here go mental at the mere mention of Electronics + Water.

 

It's true. If it's something you can completely remove power from, washing with water and soap is the BEST solution and it's the FIRST STEP on any kind of restoration project. :thumbsup:

My piece of advice:

DO NOT ATTEMPT TO WASH CPS2 B BOARDS. They suicide when you do so. :lol:

 

I had instead the problem of the moving chassis (model 1)

now I fixed it but the lens even if I fix it properly can not put up the lens properly because seems too much heavy

to understand that I took away fthe pick up (so with just the anchor) and it went up and down perfectly

Is there anything we can do about it?

Mak