dead mega CD?

Hi

I have a mega CD. I pulled it out after a few months to change oit the bios.

I pulled the old one out (thankyou sega for putting an eprom socket there) and put in one burned from a guy called iggi from the racketboy forums...

I went to turn on the unit... and nothing... its should have power but something seems about strange.

I measured the power on the power board and it seems that when the DC adapter is out, it gets 9v. when I put it in the CD console, it gets 0v, when I turn on the MD, it gets 18v. all i see on the screen is a few bits of data that the MD sometimes shows... but then nothing.

this thing was working before... what could have happened?

also I have a pain in the butt ribbon connector where the plastic support backing glue has undone it self and it takes me maybe 5 minutes to put the damn thing back together.

I tried to measure the voltage off the main circuit board from a random caps positive terminal to the ground thats gold around the PCB and got 0v...

so this makes me think that maybe my voltage regulators have died... is that uncommon to happen??

what do you guys think?

It would be easier if someone could sell me a model one sega cd power board please ^^

how can i test IC6, TR1,2,3 and 4?

is it posible that the chip was burned wrong and killed it as soon as I turned it on?

FIY guys, its not working with the new or old bios.

Just an obvious thought, but are you sure you hooked up the right power adapter?

i am using 2x 9v1.67A regulated adapters for both the MD and MCD.

both work fine... i was using the same adapters before and it was working. however there was a severe degridation in sound... I replaced all the caps in the mcd except for the audio ones so im not too sure if its just them... I can replace them tomorrow... but I have a feeling something serious has burned out.

also the fuse has been bypassed

A bad ROM should not 100% kill it, the ROM serves as a boot-loader. Put in the original ROM and see what happens, as the Genesis hardware reads the ROM in the Sega CD and then Boots, giving full power to the Sega CD. Without a working boot ROM, it will act dead for the most part. Do you get audio out from the back of the unit?

well, it has the origional rom in there now... and nothing... I will check the sound... but im pretty sure there is nothing as not even the red and green lights come on... I will also try swapping bios`s out again... baybe its a bad connection hopefully.

*edit*

finished swapping the bios`s... tried sticking them in backwards, swapped again... still nothing.

i did see however that the red and green lights lighted up for a very brief moment... and then died out sort of slowly... but then i realised i didnt plug in its power... plugged that in then nothing again.

I will quickly try the japanese PSU, see if that makes a difference

unfortunatly it didnt make a difference

I would try replacing the fuse. It is worth a shot

it doesnt have a fuse anymore... its just got a piece of hard wire instead.

i`ll see what I can pick up tomorrow at jaycar...

I'm guessing you fried something. Replacing the fuse with a hardwire is a bad, bad idea.

it was by passed along time ago. the megadrive doesnt have one and lots of other devices dont either... plus its on a regulated PSU... so im not worried so much about that. with any luck, its just a few blown voltage regs... if I am lucky.

ill post results later tomorrow

Quote:

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Originally Posted by nhm

I'm guessing you fried something. Replacing the fuse with a hardwire is a bad, bad idea.

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You beat me to it! lol Anyways, I would think that you fried something as well by not having a fuse installed.

Ahem ... Check if you didn't place the audio/power supply flat cable inverted. It has plastic spacer on one of the sides so if you insert it inverted, it's as good as if it was missing... :daze:

Quote:

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Originally Posted by m68k

I would try replacing the fuse. It is worth a shot

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I agree the Sega CD has a common issue with the stock fuses.

well, unfortunately jaycar didn`t have the stuff i needed so i will have to make a mail order from rs components. if it is because of a psu/fuse issue, its most likely to be a transistor/diode/voltage reg issue.

does anyone know how to trick the board into turning on so i can find where the fault is?

Short the collector and emitter pins of the green NEC transistor at position TR4.

I thought that might be the problem... I'll give that ago later tonight. :D

Actualy on a closer inspection, there seems to be a bit of goldy brown sort of fluid that seems to have dried up around it. It looks like its leaked from the under side... I really doubt that its glue or flux too...

so with any luck :D

I gave it a go... looks like i might be taking a step in the right direction.

I shorted the pins like you said and I saw the green and red lights turn on briefly, but it dimmed like before again... it did that twice to three times in a row but then stopped doing anything... however I have a feeling it was a fluke.

What should I do now do you think? Do you know where I could borrow someones model 1 board to do some testing and maybe even buy it :P

Honestly, I think your problem is a MAJOR electrolytic capacitor failure (like, all of them are dead).


Why they're so important ? Because they decouple the power supply, making it stable.

Most of them are decoupling capacitors but some are related to audio. So once you get it booting you might be surprised by the fact that some of it's audio sources might be muffled or completely silent.

Anyway, since you're now on the right track, good luck with the repair. Any doubt you might have, I'll try my best to aid you with. :cool:

Well, actualy, I did replace all of the caps...

stupid thing isn't working... and I've just found out I have a shit connector on the board for 9v in... so I'm going to hard wire that tonight and replace those transistors and clean all of the ribbon cable contacts.

i could use some luck right about now >_<

My opinion is maybe a transistor, so replace it
If it is a model 2 sega cd , let it die
If it is a model 1 SAVE IT!

Quote:

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Originally Posted by villahed94

My opinion is maybe a transistor, so replace it
If it is a model 2 sega cd , let it die
If it is a model 1 SAVE IT!

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LET A CONSOLE DIE BECAUSE OF HOW MANY THERE ARE OF IT BECAUSE OF IT'S MODEL!?!?!?!? HAVE YOU NO SOUL?!?!?!?!? :mad:

yeah, its a japanese model one... it is as new condition too!

i can't say I'm a fan of the model 2s... I wish all segas used an ejecting CD rom as aposed to one with a flap... like a toilet! atleast its not as bad as a jaguar :P

what I love about the model ones is they stack verticaly... its just pure genious... it makes me wonder why you would ditch the design over cost considering the advantages of space saving it has!

I recon its the transistors too... but I am very worried that the new bios chip is causing a short circuit somewhere and has popped something important on the main mobo... like an important IC chip. touch wood!

Quote:

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Originally Posted by Defolto

LET A CONSOLE DIE BECAUSE OF HOW MANY THERE ARE OF IT BECAUSE OF IT'S MODEL!?!?!?!? HAVE YOU NO SOUL?!?!?!?!? :mad:

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If it is unrepairable yes, i would, get a new one.
If not repair it to work as better as it can, but there will be a moment when it doesnpt get to work.:sorry::sorry::sorry:

New BIOS chip ? Are you going to use the new region free hacked BIOS ?

thats what I have... I just stuck it in after maybe 1~2 months of not being used... and nothing. I really should have tried to test it before I put the bios in...

Hm ... Can you take high resolution pictures of the unit internals ? I could try to help you further with such pictures.

sure, no problem...

I'm gonna be back home late tonight though... have japanese class after work. maybe in another 7 hours... god its only 3pm here...

If you need parts, I can sell you my model 1. the laser assembly is shot, but everything else is in working condition.

If anything, Model 2s should be saved, they are more robust and will last much longer after repair. The Model 1 fight is futile at best, but still worth a try in most cases.
Now, if someone could mod a modern CD-ROM assembly to work in a Sega CD, that would be great. (for future repairs)

Not at all, i´ve been using intensely my model 1, after repairs,and working.

Also by the way, i think sony still makes the kss200 used in the model 1

MEGA-CD uses KSS240A, an laser pickup with integrated preamp (an equivalent of CXA1081 is inside of the pickup photo detector die)

It's an pretty expensive SONY laser pickup intended for use on high end table/rack mount CD-Players. (that's why they changed for the cost effective KSS210 on the MEGA-CD 2.)

Also that's why the MEGA-CD1 is better at dealing with scratched discs (when new or properly re-adjusted/repaired)

For info on general CD-Player repairs I recommend forums such as DYIAudio (http://www.diyaudio.com/index.php) as they contain an extensive forum about CD-Players repair which share a lot of components with our beloved MEGA-CD. :cool:

Anyway I'm still waiting anxiously for the pictures of the boards on this MEGA-CD unit.

Also me, but maybe is a blown transistor, because that makes strange behaviour in cd units, mostly when they are as old as a sega cd

ah sorry guys for the late reply.

I got stuck back at work... and just made it on time to class, so I missed out stopping by the electronics shop.

I only got 4 hours sleep... daaamn.

Pics will come tonight.

Quote:

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Originally Posted by Lastcallhall

If you need parts, I can sell you my model 1. the laser assembly is shot, but everything else is in working condition.

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if it comes to that... i will go for it. but it would be nice to fix it.

http://img838.imageshack.us/img838/2198/cimg2100.jpg
here you can see some brown crap under the transistor.
i also measured the voltage agross that diode f1 in both directions and got 9v. that doesnt seem right to me... does that mean its the diode thats failed?

http://img691.imageshack.us/img691/7421/cimg2101n.jpg
these are where i had leaking caps. they destroyed that green inductors contacts... to that was re done... it still seems to be functioning.

http://img840.imageshack.us/img840/720/cimg2103.jpg
you can see how its leaked through the otherside. those joints that it effected were all re done. it was working good after they were replaced.

If you can make pictures of the main board too it would be great.

F1 is the fuse. It should conduct to both sides.

The big capacitors (Black electrolythic capacitors) close to the voltage regulator IC seem to have leaked. replace them. They're highly likely to leak because they're close to the voltage regulator, which is a source of heat. For best results use capacitors rated for 105Celsius being LOW ESR doesn't matter much for this case because the voltage regulator here is linear, not a buck power converter like on PC motherboards. LOW ESR capacitors work here if it's what you can find. Mostly stick to the proper rating on voltage and capacitance. And please do not replace them backwards. They explode like grenades when inverted. ;)


The capacitor on the power jack is useless.Please remove it completely.

The main board might have leaked capacitors too. Please take pictures of it (and the CD to MD connection board as it contains capacitors too). :cool:

Ah sorry I made I mistake... I mean I measured 9v difference accross the diode d1, not f1. f1 has been bypassed.

those electolytic caps are brand new... about only a month old and maybe about an hours worth of use... so they are fine.

all other caps are replaced with tantalums.

http://img842.imageshack.us/img842/1431/cimg2104.jpg

Can I ask that you resize your pics? It's hard to see everything when it's all blown up like that.