sega cd corrput internal ram

[qzack]

Thanks for the reply.

As much repair as I do $100 for a rework station may be overkill.
I just do this as a hobby and solider basic stuff in college as part of coarse in electronics engineering.
I do however appreciate the advice.

I'm still thinking that this may be more of a voltage issue than one with the actual IC modules because of the fact that I can't format it at all and get an error.
I have a multimeter at home, what would be the points on the board to check for proper voltage..? Part of this problem (formatting the ram) has to do with the voltage regulator not giving enough
so the system locks the ram to battery and makes it so you can't access it. If I were able to access it and format it then discover that my saves are corrupt or won't save, this might
explain to me the modules going bad but this is not the case.

[db Electronics]

I have a multimeter at home, what would be the points on the board to check for proper voltage..?

IC6: Battery Backup IC: MB3790 (referenced as IC9 in the schematic I linked earlier)

This IC determines which voltage supply the BRAM operates off of: the internal +5V, or the battery (when the power is off). It has a comparator built-in which automatically switches the BRAM over to the battery supply when the console's internal +5V supply drops below a certain threshold (i.e. when you turn off the system). Important pins to measure on this IC, and they're expected readings are:

Pins 13,14 - Vin - should measure +5V when console is powered up, 0V when powered off
Pin 5 - VBat - should measure around +3V regardless if powered up or not
Pins 3,4 - Vout - should measure a bit under +5V when console is powered up, and a bit under +3V when not powered

A powered state might be hard to achieve with the cover off and what not...

This is the best I can do by simply looking at that schematic, I do have two model 1 Sega CDs at home, I can conduct tests in parallel to yours to help you out over the weekend if you require.

[qzack]

Here is a dropbox link with better pictures of the IC chips.

https://www.dropbox.com/s/e3uuevz5ebet63y/SegaCD-MB.rar

I appreciate the help that you have given me. I plan to open up my model one tonight and start checking voltages.
In looking at the pictures from the drop box download above, check image DSC04807.jpg as it is a nice pic of the model one motherboard.

This board layout is the same as mine I'm pretty sure.

This should give you the right IC numbers as they are clearly seen. Let me know if by some chance you want me to check another IC....

Thank you again for helping me.

[db Electronics]

Those pictures are of a different revision than your original picture. While most ICs look like they're in the same place, the reference designators are not the same, be weary of that. These new pics on Dropbox do line up with the schematics I provided however, hopefully this is the same revision as your unit.

[AlmostOriginal]

Here is another image which should do the job.

http://img20.imageshack.us/img20/4789/dsc0439td.jpg

Yay, thats my picture / Mega CD!

[qzack]

I hope you don't mind me borrowing it then
I appreciate it as I wasn't at home to take pics of my board but it matches perfectly.

[AlmostOriginal]

No problem! I always keep looking for my own pictures in case some one would use it for scam or claiming they took the pictures. But since you using it for "fair" use i don't complain. I hope you can get your Sega CD back together soon. Sadly i can not help since i am not smart enought to be at any help.

[douglie007]

heres IC16 forsale http://www.mcmelectronics.com/product/P-MB8464A and I get a dealer price from there so if you want to try I will call and see how much it would be for me to buy for you

[qzack]

Ok. I totally messed up. F$!?ed up is more like it.

I had just ordered a cap kit to start replacing some of the smaller circle (game gear) caps.
When I went to remove C43 it pulled one of the solder pads off the board. Where can I run a jumper wire
to compete the circuit...? The pad is totally gone. I was careful in trying to remove the cap but apparently not
enough. This is on my unit with the ram issue.

On the other unit I have combed the board looking for damage and it's impossible to know where to start. So now
I have two dead sega cds. One that freezes on boot up and the other with a pad I broke off with no access to the ram.

Before I started the cap replacement on the one board I took voltage readings on the IC 16 and they are way low below 3 volts. The board that freezes on boot, I took voltage readings on it and got around 2.2v

[douglie007]

always add solder to the pad before removing it, it lowers the melting point of the existing solder. do you have a pic ?

[qzack]

Yes.
It was the Positive Pad (+) on C43 that I messed up. The negative is fine and intact.

https://drive.google.com/file/d/0B_Y...it?usp=sharing

[qzack]

I fixed the damaged pad by "carefully" scraping the board to reveal some copper and soldered the cap. My sega cd behaves no different than it did before the cap replacement on the main board.
I have not replaced the caps on the power board as of yet.

I also left the two 100uf caps on the main cpu board alone as I don't think by replacing them my memory format problem is going to be fixed.

I am glad that my unit has returned to normal function. I did play a few games and it doesn't act any different than it did before. I'm not sure what C43 does but I must of fixed it
or I think I would be experiencing some king of additional problem than just being unable to format the ram at this point.

[Xalphenos]

Hey qzack I responded to one of your threads regarding this issue a while back. Well I have an update. I did a full cap replacement and it didn't fix my ram problem either. I really didn't expect it to though. Then I tried re flowing the ram chip, again that didn't work. Then I used some chipquick and removed the old ram and soldered in a KM6264BLG-10, which I had researched a month or more ago. Fired up the system and was able to format the ram first try. So far it seems to be working great. Unfortunately I can't test the ram further because the system wont read any discs. I replaced the laser in it at the same time but that didn't seem to help in that regard.

There is a guy on ebay selling the ram chips for about US $10 shipped.

EDIT: Oh yeah thanks db electronics I used your information to check for voltage on IC6 to make sure that was working as well.

And for all you "pics or it didn't happen" people.
http://imgur.com/LOI6vj8
Not my best and I haven't cleaned up the flux, but the system is still essentially useless so...

[douglie007]

Hey qzack I responded to one of your threads regarding this issue a while back. Well I have an update. I did a full cap replacement and it didn't fix my ram problem either. I really didn't expect it to though. Then I tried re flowing the ram chip, again that didn't work. Then I used some chipquick and removed the old ram and soldered in a KM6264BLG-10, which I had researched a month or more ago. Fired up the system and was able to format the ram first try. So far it seems to be working great. Unfortunately I can't test the ram further because the system wont read any discs. I replaced the laser in it at the same time but that didn't seem to help in that regard.

There is a guy on ebay selling the ram chips for about US $10 shipped.

EDIT: Oh yeah thanks db electronics I used your information to check for voltage on IC6 to make sure that was working as well.

And for all you "pics or it didn't happen" people.
http://imgur.com/LOI6vj8
Not my best and I haven't cleaned up the flux, but the system is still essentially useless so...

The replaced chip did it format to 125 blocks or larger? if larger I might get one

[Xalphenos]

No it wasn't any larger. It is exactly the same as the original. You got me thinking now though. Does anyone know of a larger memory chip that would be compatible?