Sega CD-2 no power craziness !!!

Hi,

I really don't get it, and I need some help...

I bought a Sega CD model-2 from ebay which was not working, no power, and no display, however it was not the fuse before I get angry replies, the power LED doesn't come on, and I can see continuous laser beam inside which disappears if I close the led switch the laser stops, the screen is black, however when I flip my modded Mega drive switch to other regions I get the wrong region screen...

I tried the following (I do work with electronics and I have 20+ years of experience with soldering etc so cold solder etc is not a factor over here).

1- I checked all caps, all were fine, I took some which I suspected out and tested with ESR meter replaced which ever suspected (1 or 2).

2- fuse is working of course as I said.

3- transistor Q301 is fine, also tried another similar one I have no effect.

2- Q302 is also fine, took it out checked it, even replaced it with a working one from a parts mega cd I have, no effect, so I restored the original.

3- Q401 took out, same thing, not effecting.

4- voltage regulator replaced.

5- dioides d301 , 401 , 601 tested, all working fine.

6- applied flux to the cpu contacts and gave it heat gun to reflow, no effect.

7- I went crazy so I thought maybe the bios chip is gone, so I took it out, replaced it with a biod from a PAL mega cd 2 , it changed the region to PAL, now it gives black screen which I put mega drive region switch on PAL, and gives wrong region screen on the NTSC UC & JAP positions, so it was not the bios chip either !

the board looks so clean, not missed up, so what do I do from here? is there a major IC dead (which I cant really check its beyond my capabilities and available tools)?

(Note: please don't ask for photos, it wont help, no cold solder bla bla issues over here, if you have seen similar cases of complicated no-power sega cd, just please give me a hint, or suggestion)

Thanks a lot in advance...

 

[Redacted, it's late..]

 

just hoping for some help please,, thnx

 

So the power LED doesn't work, but there seems to be power? Have you checked that the polarity of the power flow through the system is correct? And that the LED works?

 

As lame as this may sound I'd ensure that the edge connector is clean and that all of them make proper contact. Kinda sounds like its not communicating with the genesis. And have you tried running a game?

Also, ensure that the av out pins are not cold. I have seen some that were cold despite looking perfectly fine.

 

Check the voltage regulator if you used a pull from another system, and check the connector to the genesis, please post Photos, there are a lot of revisions

 

the led works, because once i kept switching on and off for tens of times it worked for less than a second then went off again, polarity of the power supply? i use a genesis power supply center is negative..

thnx for the ideas, but av is through the genesis mega drive and it works fine i use it to play sometimes, running a game doesn't do anything, the laser beam is coming with cover switch open , in this case no laser should come , unless i close the cover switch , so it doesn't read cds of course, regarding the contacts they look shiny however i will give them an alcohol clean once more ..

both voltage regulators are good, however i can try them once more, do you suggest a certain test for them?

thank you all for replying and still hoping for more help please

 

update, tried to clean contacts of slot of sega cd , snd even expansion port of mega drive, that didn't help ..

so any other clues plz?

 

There are 2 major board revision. It would help knowing which version. Does the drive connect with 1 cable or 3

 

hi , thanks for replying, its the 3 cables version

 

That probably rules out a drive communication problem. Can you get an actual Sega Genesis? I have seen weird glitches and crashes that are specific to revisions of the Sega Genesis. One example is lunar ii crashes if it detects a ram cart through a 32x and model 1 Sega Genesis. It’s possible that the bios is crashing due to a hardware revision that it was never designed to account for,

 

hi, first of all thanks for your reply, and to not to think that I am a stubborn person, I tried it again with a mega drive 2 other than my original moded sega genesis 1, same behavior.

your theory is good, but its not applicable here because if it was just a hardware glitch preventing bios from taking off then at least I would have got the LED to light up, but there is something else.. and major as it appears..

still open to any ideas or suggestions, thanks in advance

 

any further suggestions?

 

This is the point where I would parts bin it.
Edit: to put it simply at this point it is probably an ic chip, cracked trace or bad solder joint somewhere, the next thing to do is take chips and swap with a known good board, highly risky and not recommended

 

Use an ohms meter to check every trace. Other than that it could a be a dead chip. Testing every trace is going to be hell and generally gives me tunnel vision. I like to take a sticky note and cover an area that I have tested as I go along. This will rule out redundant testing that happens when you are burning the candle at both ends. I use a sharpie to mark a trace that I have found faulty. (Sharpie comes off with a wipe of alcohol.) Best of luck.

 

Thanks alot , I will try that out.

 

Thanks alot , I will keep that on mind

 

At this rate I would just throw it back up on eBay, someone can use the shell or laser. You never know what someone else did to it before hand, it's always a gamble buying broken stuff as they will lie about it and claim it's untested or they couldn't get it to work and just gave up on it etc.

 

If the LED cannot light up despite it working, won't it mean that the current is going elsewhere (i.e. short circuit)?

 

well said, any suggestions / methods to tackle that? known parts to start from ? as I said individual parts on my mind were found working including the voltage regulator ic301..