After repairing my mega cd , ended up destroyed i guess :(

hello,


i posted it by mistake in sega discussion, sorry for that..


i really need some help with my mega cd (pal) , it was left for long not working, recently thought of repairing it , i did the following:

replaced laser
replaced potentiometers as i felt they were lose, but it wasnt them preventing games from loading
replaced all laser board caps as 2 were dead (OL on esr).
replaced all motherboard caps, made a huuuge mess out of many , but gave them jumpers from here and there,
jumpered the fuse..

well, it worked pretty well, all ok, even audio was fine except that certain audios were not coming through the mega cd audio out, including the (taa daa) at sega logo , sonic spinning sounds in sonic cd, his spinning sound, rings taken sounds etc, but those were coming through the mega drive audio out.

so i was fine with that, assembled it, then i played sonic cd , guess what, sound started crashing it first stage, it even once gave me both lights blinking and cd ejected, even in audio players tracks were reading just crashing noise, i found one cap came out from mb, points were gone, gave it jumpers, no use (bios main music was ok all time, only in game sound was destroyed)

then i thought of going to power board, found 2 bad caps near the right side (the 100 uf) replaced them, then thought of replacing all caps (all remaining are 10 uf), which was baaaaaaad idea, old and cold solder caused many bad points, well somewhat i guess i replaced all

tried it again, now wooorse, no music at all in the game just noise (earlier i was getting music of sonic cd opening screen, beginning of stage , then crashes)

went to check solders again of power board, found something toooo weired, the negative side of about 7 caps was no giving closed circuit with earth !! so I got a stupid idea which i did

i gave all those negatives of all those caps an earth jumper, tested it.. frozen screen of bios

removed the jumper, now only frozen screen of bios..

is it gone? totally?

i feel deeeeply sad , i have above average to good electronics experience, but i ended up doing this

please help me, thanks

 

Have you got pictures of your repairs?

 

well i don't have of all but i will try to take some if thats too important

what matters now that is the symptoms (frozen bios screen) mean full death of the console? did i burn the cpu by that jumper which i added to negatives of caps then removed?

 

It's very possible. That's why pictures would be helpful to see where the damage is and where jumpers were attached.

 

That's normal, the mega cd audio out is meant to be a mixer, you need to connect the Megadrive to it with a jack cable to get both consoles output.

 

Droid III is right, you need a mixing cable to get all audio through the RCA jacks on the Mega CD. However, you can get both MD and MCD audio via the audio outputs on the MD itself without the need of a mixing cable. The headphone jack on my Model 1 and the stereo output on my Model 2's miniDIN connector are what I use for this.

Now the 32X is a different story...

 

thank you droid iii & monkeyboyjoey , but what made me do the jumper which destroyed everything before i remove it (but that was too late) is the scratchy audio in game and in audio player although bios sound was normal and fmv audio was normal too !!

but for the current status, freezing bios frame with no lights, is there any chance that this is repairable??

thnx again

 

one more important thing is that maaaaany caps smds or electrolyte their negative terminal is not getting an earth connection, why is that? my understanding is that all negative terminals should give continuity with earth .. which part could be doing this?

and what is the name of this black component pleaee ?

 

and for photos of current status, here are some, but please note ... it was working like that without a problem, then sound started getting scratchy, then i tried giving all caps negative jumpers manually, then it went frozen or dead, even after removing all jumpers...

 

The black box is L2, a choke coil.

There's a few damaged pads and C44 and C46 are missing. C45 looks bridged and cold. Several others look like cold joins. Did u use solder flux when soldering new caps?

At this point I would recommend sending it to a professional to rebuild those points and recap. Hopefully it's still salvageable.

 

i agree with you regarding cold solders, however with all of your comments it was working, stopped working just after giving jumpers no negatives of caps , there isn't any missing cap i guess but i will check .. but appreciate your reply

 

That is not correct. While many caps are indeed connected to ground, not all of them are. By connecting all of them to ground you will have shorted a lot of things on the board, and a lot of things could have died as a result.

 

ok this is indeed a highly useful reply, and quite late too, Iam basically a Mechanical Engineer however my hobby since childhood is electronics with above average experience, but at the end of the day human errors will always occur mainly when you feel sleepy while working.. also this reply indicates that the damage is mostly veeery high due to that stupid jumper of mine..

So if I may ask, where does negative come to other caps? does it come during power on only? and by which component?

thnx again..

 

An electrolytic capacitor may be used in a circuit where the positive leg will have a higher potential than the negative leg. It will still be biased correctly if the positive leg is at 5v and the negative leg is at 3v.

 

thnx for the info, but if I may ask , do all the caps negative leg have to give continuity? in other words : will they all have a common source of negative?

thnx again..

 

Not necessarily.

 

ok cool , thnx alot really

 

Maybe you can find a cheap one with a faulty laser and get it up and running by replacing it with yours.

 

well ya know but do you know what feels so sad? is that i repaired it all the way to the level in this video, replaced all caps, aligned the new laser, even replaced the potentiometers, and it worked fine, just frustration drove me to try an unproven theory ended up burning something big..

here is the link



thnx anyway

 

i don't know why but the site refuses to upload the gifs of the mega cd before it died..