Sega CD model 1 power problem.

I can't seem to upload them as they are to big but here is a rar file for them: https://www.dropbox.com/s/e3uuevz5ebet63y/SegaCD-MB.rar

 

Yes, the board needs repairs.

The capacitors at positions C28/C31 (near the WORD RAM chips) and C11/C12 near the SUB CPU WORK RAM leaked and caused trace damage to the pass through metalized holes.

 

So I need to replace those capacitors (at least) and something else?

 

No, the old capacitor leaked goo which corroded the copper traces near it. The traces need to be patched.

 

Which traces? And how do I do that?

 

I can't help you with that remotely, you would either have the knowledge and tools for measuring the board traces for continuity or send it to someone who can do the repair for you. Considering your geographical location, you might want to contact this guy at this very forum: Bad_Ad84
http://www.assemblergames.com/forums/member.php?63433-Bad_Ad84

 

Checking for continuity is easy. So I should check which traces those are, check continuity between points on the board between connecting points and if those are broken use wire to connect them. Right?

 

Word RAM is the two long ZIP package chips which are close to the leds (2x 16BIT by 64KB DRAM chips).

WORK RAM is the four ZIP chips near the connector that goes to the CD drive. The WORK RAM is 4 128KB by 4bits DRAM chips.

Both RAM banks go to the large SEGA ASIC (315-5548) and without them the SUB CPU won't be able to start, as it's program is unpacked and written to these RAMs by the Mega Drive 68000 during boot.

Edit: Just to be very clear, the LEDs are controlled by the SUB-CPU so if it can't start, they will never light up.

 

So if I get it right, the SUB-CPU can start on mine but can't connect to the RAM banks well?

 

No, no RAM = no lights, no Boot, no video.

Depending on the version of the BIOS, you will get the clouds background without the MEGA-CD logo or just solid black screen. The MEGA DRIVE can run but not the MEGA-CD CPU.

The MEGA-CD CPU cannot work without the RAM because it doesn't have a BOOT ROM. It needs the MEGA DRIVE CPU put it's BIOS on the VERY RAM that isn't working right now.

 

hate it when caps ooze nasty goo. much prefer it when they go pop or just dry up

 

So check RAM connections?

 

My launch day Japanese MEGA-CD almost died a nasty death to bad caps goo. When I removed the bad caps the board had just got hit with the fluid from them.
Apparently the capacitor leaks when you power it on after a long while off. It just boils and let the liquid exit by the bottom.

At first it's transparent, but sticky. Then it dries oxidizes and becomes black. That's when it starts to attack the board.

Basically, yes. That's what I've been saying ever since I saw the pictures. And if you don't feel like you're capable of repairing it, Bad_Ad84 is on the next country. He surely can help you with it.

 

yeah i see this happen with one of the power caps on a game gear, stuff is nasty and does a good job of eating up boards, never actually seen it ooze before until then, just the leaked stuff that had already leaked.

 

Yea I had to replace the caps in both my model 1 Sega/Mega CD's. Got some pics here

http://www.sega-16.com/forum/showth...-repair-thread&p=546388&viewfull=1#post546388

 

I've replaced all caps, that didn't seem to help...

 

Need to repair damage too

 

You seem to fail to understand that we're telling you to repair the damage caused by the stuff that leaked from the capacitors. It can bee seen in your pictures that your board has damage from oxidization.

 

I'm aware, but I first wanted to do the easy things and hoping that that fixed it. Or that someone more local came to the rescue.

 

l_oliveira doesn't waste his breath when telling you what the problem is.