Sega CD Model 2 No Power

I've gotta sega cd that's been nothing but problems for me since I've gotten it...

1. I got it in a somewhat working condition the adapter included was under amperage so it wouldn't read discs based on that.

2. In-between buying a new adapter and troubleshooting the disc drive board had gotten broken thanks to an idiot roommate, so I soldered a different replacement board on I picked up off craigslist.

3. Upon plugging in the new adapter I made the mistake of trusting the same idiot roommate and the voltage was set incorrectly to 12V(I asked him to switch it to 9v as he was plugging it in while I was moving crap around), blew the fuse.

4. Bypassed the fuse by jumping directly with a wire and made 100% sure my adapter was set to 9v, I had been looking into getting a new fuse but in the mean time my console was finally working...
Played mickey mania and a few other things for the first time and put the thing away (left plugged in).

5. Today moved all my stuff around and the genesis/sega cd nearly fell down went for a bit of a bumpy ride ( My electricity also went out between this but I've got the console hooked to a surge protector )...
Now the console doesn't power on at all.

Did I blow another fuse?,
Is there anything I should check?

I'm gonna be getting another multimeter soon (some how in my house shit disappears even though you don't misplace it),
Any points specifically I should check?

Can someone also suggest a replacement fuse from Radioshack that would suit the already common blown one as well as any other caps or fuses I may've blown being an idiot.

This is the one I've jumped:


Edit:

Also I haven't noticed any leaky caps, or anything looking/smelling burned/blown.

 

You bypassed the fuse and didn't put in a new fuse later? That's just stupid. Enjoy your new parts console.

 

Yeah, I was careless but I only did it to see if I was wasting my time trying to fix it (If it wasn't gonna work if I added a new one)

The stupid thing I did was didn't unplug it after I tested it out...

It's been sitting since then till now, and I understand it was stupid and careless I didn't think to unplug the thing as I wasn't using it.

Are you 100% sure it's fried at that point?
it's not like I've fucked with it at all since the fuse was bypassed besides testing it once.

I assumed it would've blown a cap or something without the fuse in-tact I'm not that experienced with electronics.

 

12V would not blow it. Reversed polarity CERTAINLY does, though.

Listen to this wise piece of advice: Avoid at any costs using universal power supplies (of the kind which allows for polarity reversion) or power supplies you're not sure of their polarity.

Due to the fact that MOST equipment using barrel style plugs have + on center and SEGA stuff follows the Nintendo standard of having negative on center, you're asking for trouble if you use any power supply on the SEGA/MEGA-CD.

As per why it's not protected with blocking diodes (the Mega Drive/SEGA Genesis unit is actually protected against polarity reversion) such a protection would cause a voltage drop which cause the MD/Genesis original "power brick" unsuitable for powering the CD unit. So they did choose to use a fuse instead.

Unfortunately when such accidents happen a power cut off transistor (A NEC 3 pin green part near the power circuitry) will be short-circuited or open. That's what prevents the machine from powering up. You need to replace that and the fuse now.

 

Have any pictures of the NEC 3 pin?,
And would there be anything else possibly damaged considering the fuse wasn't intact?

Also the 12v isn't what blew this pin you've mentioned if that is damaged,
It only blew the fuse...
As it was working properly after bypassing the fuse which after bypassing it is when I was using a 9v adapter with the proper polarity (I double checked this before plugging it in, after bypassing the fuse).

As I was saying above the console had been functional (as far as I know I hadn't tested it before doing this except for like a week before ) until it slid down my TV ( I had it on top of it, and moved my table like an idiot ) in a rather rough manner, but with the fuse still bypassed so I'm assuming additional components may have been fried due to the fuse not being in-place.

Regardless if you could give any more information or pictures about this "NEC 3 Pin",
I'd greatly appreciate it as well as any additional advice.

 

it's a transistor. A green 3 legged thing which is mounted near the power circuit. If you give me a picture of the board I can point you where it is.

Anyway you better taking it to someone who understand a little bit of electronics. Having a proper fuse in place would have saved the transistor from blowing. That's what APE was talking about.

 

I know a bit about electronics...

I was just being careless/lazy.

I intended on replacing the fuse with a proper one but ran into an issue at radio shack where I couldn't find the right size holder/case for the fuses, and got annoyed so I didn't deal with it.

 

There's no case for that fuse as it's surface mounted... lol

 

I meant an alternative fuse, not an exact replacement man.

 

So I did a bit of research, I guess the Resistor you're talking about would only be present on a model 1 and it's labeled either TR3 or TR4 on the board.

I suspect my issue may be the voltage regulator at Q301 I believe it is,
The voltage regulator is B963, I'm honestly not sure how to test it.

I'm also looking for any other transistors being present on the board.. and trying to find my fluke.

EDIT:
I've taken as many pictures of the board as I could for you in the highest quality I could there may be some of the same stuff but the pictures seemed a bit blurred so I figured re-taking them and using both in-case some parts were blurred and others weren't.

I also haven't seen very many pictures of the board online so hope this thread ends up helping other people along the way,
So far I've found various articles where people solved the problem similar to mine but never actually gave the solution and just disappeared.

http://imgur.com/a/3yuTH

 

Q301 is the green part I was talking about. Q302 (the small one on the other side) controls it. So both need to be checked.

 

oh guys tip for model one owners tr1 can go aswell.
fixed one a while back.

 

I have the Sega CD same model same issue, I put in a restable fuse and replaced Q301 with TIP127G but I cant see what Q302 should be, its reading an open on all legs and I should read some resistors in the chip.

 

take a look at the sega service manual you can download them.

 

The Sega Manuals are good, but the original PNP and NPN are not made anymore and I cant find a good cross reference, I'm going to try and get a tip122 that is the NPN that is the opposite of the PNP TIP127.

 

Q302 is listed as 2SC2812-5-CP-TB, 2SC2812-6-CP-TB, 2SC4362 and UN221L. The first two are for the SegaCD and the last two are for the MegaCD. Not sure why it lists four different parts in the component sheet but there you go.