MVS MV1FZ hav video error 00008000 5555 0000

[davidcoolman]

Dear NLG community,
I recently got a pair of 'non working' MVS MV1FZ slots in a garage sell and I request some of your knowledge to repair them.
One has no sound, but i'll keep that one for later since it doesn't look too bad 
The one who's worrying me more is  halting on boot with:

Video ram error
00008000 5555 0000

After searching a bit i found that it was pointing to (both?) fast ram (CXK5814) chips, however changing them do not guaranty repair:
It appears it's relevant to check continuity between chips (LSPC2-A2 to CXK5814)

I found pinouts for LSPC2-A2 (thanks to http://wiki.neogeodev.org, this seem to be a BIG reference ), but not for the ram chip (they actually need the information)

My question is what are the pins pairs i need to check to diagnose?

Thank you by advance

PS the board doesn't look rusty or physically damaged

[channelmaniac]

Unless there is clear physical damage to the board, the RAM will most likely be bad.

Since you are getting "0000" as read back from the chip, check the R/W, /OE, and /CE pins for activity. One of the enable pins may be tied to ground, I forget off hand if that was done on the NG boards... but that's a common trick used by hardware developers.

If you have the proper activity, replace the RAMs. They are VERY common to go bad.

For the one with no sound, check the traces around the battery for corrosion damage. If that's not it then replace the caps in the sound section.

RJ

[davidcoolman]

Tanks a lot Mr Channelmaniac
I still have to figure out what the pins are but ill Google That and learn something

For the no sound mvs it is weirder in fact the neo geo welcome sound is very slow and after That nothing...

The amplifier has obviously Been changed who knows why...
There is no corrosion i read somewhere, maybe from u these batteries are timebombs so i removed booth but no leaks...

By the way tank you for your quick answer, and for all your contributions in general.

Dav

[davidcoolman]

I found à french blog where you also helped with this ram error
I checked pins 1 to 8 , 9, and 24 to 18 had continuity the other pins are for data input output

http://pdf1.alldatasheet.com/datasheet-pdf/view/47128/SONY/CXK5814P-35L/+35Q_9UOLLXaE/1MvDtCXpDGV+/datasheet.pdf
 
I guess i have to order a pair of new ones,

I will keep u in touch

[davidcoolman]

As expected, Mr Channelmaniac was right,
I changed the fast ram that just came from hongkong and the problem was solved!
however, i must warn newbees like me that de-soldering intergated circuits is a pain in the @..
i damaged a coupla traces so i had to fix them back. not suggest people not used to these manipulations just cut the old chip and resold on leftover pins,
but that's just a suggestion.
thank again Channelmaniac!
I can now work on the bord having sound issues but i'll start a new topic.
Best regards,
dav

[channelmaniac]

Congrats!!!!

If your problem is missing audio or very low audio then replace the capacitors in the audio section of the board. Bad caps are a common problem.

[davidcoolman]

Merry xmas to all!
I finaly had Time to play with my mvs but something is weired:
The brightness is blinking frequently like everything 15seconds.
I duno if it was prior my repair or after it...
The only thing i know is i accident l'y removed a tiny yellow stuff underneath the board which i suspect to be a capa or à resistor...
I replaced it but i m not sure it s still ok...
Anybody has specs of these components?
Thanks

[channelmaniac]

Most likely no on specs...

Look to see if the part has connections to power on one side and ground on the other. If so, it's a simple power bypass cap to filter the power lines going to the chips. Bypass caps generally run between .01 to .1uf.

[davidcoolman]

Hi Channelmaniac, great reading from u!
i haven't tried yet to check the voltage/ground linkage on the tiny 'capacitors'
i actually had the same symptom with the other 'no-sound' MVS so i started to blame the PSU, nd changed it with no result...
i took everything back to my old CRT test-TV and everything was fine...
...the weired blinking stuff comes from the plasma HDTV... damned you Samsung!
could it be some sync problem...
however, i well recall using my RGB PS2 on this HDTV with no such problem.

maybe i made something wrong with the scart adapter basically following this but without any resistors:
http://www.geocities.ws/podernixie/htpc/jamma2euro.gif

still needs investigation, cause even if the image is crappy on this 50 inch TV, it's kinda fun playin' with friends in the living room and not in the basement for some reason...
 

[channelmaniac]

The Neo Geo is well known as having a sync signal that drives some TVs crazy. You may want to post over on the Neo Geo forums to see if those guys have any ideas on cleaning up the signal a bit.

[starzag]

Hello, everyone.
I am new to this forum and I really don't know how it works.
I have two boards : MV-1A and MV-1FZ with different issues.
MV-1A coin switch 1and 2 worked in input test, but it did not take credits if I want to play game.
MV-1FZ had a graphics problem like "insert coin" sign was corrupted.
On both boards I did power up without cartridge and all dip switches down and started getting "back up ram error" ,
which does not want to go away. For MV-1FZ I even changed the ram 3 and 4, no result.
really strange. What I notice is that ram 4 has no activity on 2 data bus lines 5 and 8, which come from Bios chip.
Do you have any suggestions?

[channelmaniac]

Check continuity on the traces. You may have a gouge on the board that has cut them.

Also check for proper operation of the chip select/enable lines and the read/write line. If you don't know those pins, grab the datasheet for the chip from www.datasheetarchive.com

Raymond

[starzag]

Hi,Raymond
Thanks for the reply. I am not sure that open traces are my case.
Initial problem of MV-1FZ was that coin switch did work in test mode, but not in real.
All I did is, power up the board w/o cartridge and i don't know why , all dip switches down.
And I got back up ram error ever since. No repairs were done, for that reason I don't suspect open traces.
The only thing I think could be the relation between the coin issue and back up rams.
It is really weird, basically because it happened on the 1A board too( i mean dip switches and back up ram), which had graphics problem.
I don't know what happen, it is beyond my knowledge.
Roumen