sega cdx issue/ need advice or parts

I have a SEGA CDX that has a faulty bottom board (the one with the cart slot). I narrowed it down by swapping boards between another CDX but ill describe the symptoms just in case there is someone out there who knows a easy fix or any. I have replaced the motor/housing and the laser (sfc93aq) so its not that or the top board, or the ribbon cable.

When it powers on there is no response from laser, doesn’t slide position or attempts to focus.

The motor doesn’t spin at all when powered.

The display comes on but all that shows up is the image of the earth but the “SEGA CD” text isn’t there, just “1993 SEGA Ver. 2.21” in the top right

The lcd only displays “GAME”

It wont register if the door is open or not

And every so often it appears to lose and regain sync

so what do you think? Bad caps? Fried bios? If anyone has a ideas im open to it, I have a caps kit on the way but im not confident that it will do the job. I have a vague recollection from a post I saw years ago that may have described something similar about the display and the response was the issue was a dead bios.

Im thinking that im going to need a new board, if anyone a spare and could part with it id be very thankful, id pay whatevers fair or trade say... a new cdx laser or install one for you ( ive done it plenty of times) or whatever let me know.



cheers

 

I remember seeing a similar post before and I think the BIOS was the issue. You could get a new region-free BIOS to replace it with. You can order one from someone here on ASSEMbler games or program a 40-Pin EPROM with one of the files found here:

http://assemblergames.com/l/threads/region-free-bios-for-mega-cd-version-2-00.54254/

 

thanks for that, if anyone knows who i can get a region-free BIOS from im keen. but id still want a spare board just in case that don't work
if any one else wants to weigh in im still checking in
thanks all

 

Caps or BIOS is what it sounds like. They do have a hacked BIOS for the CDX, but its next to impossible to find a chip to flash.

BIOS; http://www.sega-16.com/forum/showthread.php?15605-Multimega-CDX-Region-mod-thread

 

Could be a BIOS issue but I think that symptom can also occur if the two boards don't communicate with each other. I doubt it is a cap issue since the caps on board are for the +5v power rail and while that could cause that symptom it is more likely it would not boot. Check around your Sega ASIC chips, these systems can get corroded pins by the cart slot from age. It's a really common trouble spot.

FYI, you will get that outer space image with no "Sega CD" text if you run the top board without the CD board. Very possible your problem is the Sega CD ASIC (upper left chip right beneath the cart slot).

 

hey cheers segasonicfan, its quite optune that you came across my post! I have been hoping to get a reply from you over at digitpress. Its probably bad form to spam cross forum so ill just give a link, could you please take a moment to give it a read
thanks
http://forum.digitpress.com/forum/s...out-opening-the-console&p=2023614#post2023614

 

Hey, yeah I don't really go onto digitpress ever...but I just looked at your post and I think you would find this thread useful:
http://www.sega-16.com/forum/showth...er-replacement&p=620535&viewfull=1#post620535

I've not actually used an oscilloscope on a CDX yet because these adjustments have always worked for me. If you compare your pots and readings with the image in that post you should be OK. If you want to use an oscilloscope just follow the Mega CD 2 Service Manual that is floating around the net (also on Sega-16 forums). You just need a scope that does 20Mhz. but honestly I've had great success just adjusting to these pot values (which you should only have to do if someone messed with them, otherwise your laser is probably a dud). Don't ever adjust the pot on the laser itself...

-Segasonicfan

 

cheers, yeah ive usually just had to swap out the laser and its been good to go, i tried those adjustments with the multimeter ref and they were way off with the T.Gain, but this is with a revision that docent have the jumper between the two boards, this seems to be more uncommon as far as i have seen so i may be out of luck. oh well, you cant have too many spares

 

T.Gain and the other pots should have nothing to do with the revision you are talking about. The boards (and settings) are almost identical, the only changes among revisions I have seen being related to the analog audio output mixing stage. I've never seen a CDX that had a different setting for T. Gain, and there isn't any reason it should other than someone messing with the pot at some point. That jumper wire is nothing but an added ground, removed in later boards I believe because they found it was unnecessary.

Also, if you are adjusting the pots with the system running, make sure to use an insulated driver as it is really easy to short the pins inside them with a regular driver.

 

You shouldn't adjust laser mechs blindly, nor would reading other potentiometers give accurate results. Follow the correct procedure as per the service manual - which would probably require an oscilloscope and special test CD. And you shouldn't use a screwdriver to adjust live pots - use a trimmer tool. Given those symptoms, though, you shouldn't be adjusting them at all.

If a board isn't working, you should at least be checking your voltages to narrow it down before you try switching components because it might be that one.

 

agreed, if you have access to those things. Not everyone does though, and this method has worked for repairing CDX's in the past for me, which is why I share it. Granted, these lasers run ~$20 on ebay right now so it's not exactly the riskiest thing.
To clarify, this is addressing another CDX issue he is having (with another unit I presume) described in the digitpress forum link. Sounds like the laser he got was a dud, but putting these pots to stock or "near stock" settings will help eliminate some issues.

-Segasonicfan

 

CDXs are easy to break. Don't fuck around with them blindly like an idiot.

 

dylbob42 looks like it might be your lucky day:
http://www.ebay.com/itm/Sega-Genesi..._DefaultDomain_0&hash=item28020569c2#viTabs_0

might be worth sending an offer to this guy. youd have to swap your laser assembly and LCD and HOPE this board works. Still, they dont show up often. Very rarely actually.

 

cheers all,
In the past i haven't needed to do anything but replace the laser, and i only adjusted the pots after i found a reference segasonicfan had provided. But you cant win them all,your bound to get stung once and a while when you buy cheap AS IS FOR PARTS, anyway its situations like these that set you down a path to learn new things.Im getting around to ordering a oscilloscope, put that service manual so some use. interesting read, they would adjust units to play damaged cd's.
But it looks like i missed out on that board . i did save that search on ebay so i may get lucky, thanks anyway i appreciate the effort. i did managed to get a cdx for $20, guy said it was badly corroded so but i may be able to pick at it for parts. worth the 20 just for the shell, ive seen cdx going for cheap because the window was missing or the battery door was ripped off, no one wants a ugly unit.

 

yeah, that's an amazing price for a broken unit. I'm looking for ONE of the bottom screws for my case, if you ever come across an extra I also have an extra metal shield plate, and some other extra bits if you are looking for any missing pieces. And that little resistor looking thing soldered to the copper on the bottom board is actually a CAPACITOR - took me forever to learn that, lol.

I've also repaired a lot of these units and one that was REALLY corroded with leaking electrolyte all over the power board. I've documented a lot of info on the DC-DC board and a lot of other stuff on this console, should you need help with that unit.

 

yeah that cap, you gotta be weary of that one. i noticed console 5 were stocking them but not atm. send me your address ill send you a screw in about a week, (ill be out of town) i just did a autopsy on that $20 cdx
you cant tell but the entire inside is covered in a fine rust dust, that chunk of rust is what was the ground shield, no sign of that cap

and what was left of the shield.....

the scary part is that when i asked the seller what was the story and what swamp did he drag it out of, he said he got this from another seller and he was surprised than it even turned on......? i was more surprised that he event attempted it! when you open the door massive chunks of rust fall out!

for parts indeed, hes dead jim. all that in the red is either rusted out or dead copper. the rest is pristine
and some how cleaned up ok

at least i got a working power board out of the the deal

top board is looking promising besides a via or two, tossed the laser because the magnet turned it into a ball of rust shards but the motors and housing look good after a clean, i bet someone out the needs that little spring

 

My goodness that looks horrible! How does this even happen? Did the original owner throw it in a swamp for 20 years and then decide to sell it? Wow. Glad to see some parts are still good on it.

 

that was pretty much my reaction , and almost word for word what i asked him. still cant believe it powers on

 

used grandpa's rusty nail cleaning trick, soaked in coke for a couple of hours and lifted off quite a bit of rust. made the coke taste like shit tho

 

HOLY 7#642! that sure takes the cake on nasty consoles! I had a rusted out Saturn last month and it doesn't hold a candle to this poor bastard. Amazing the CD board turned out OK though. btw, if you use a hot air reflow station you might even be able to save that top board (IF the traces survived, which is a big "if") Those Sega ASICs are the same in model 2 Gennys. Nice you a got the power board board though! Everything working OK on it?
btw, I have a blown output on my IC21 (315-5619), let me know if you decide you can part with that chip on the rusted board. It's only used in the CDX :/ Hopefully you can get this one working though! I recommend a LOT of isproplyne alcohol and ear swabs. Send us pics of those rusted ASICS, Im super curious