MV-1 "Work RAM Error"

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
This error message in my 1-slot US Neo cab was intermittant for a while but now it appears every time I boot up. I have the standard US BIOS and the oldest hardware rev of the 1-slot board out there (MV-1, with joystick connectors and memory card reader support). When I boot up, here's what appears on the screen:

WORK RAM ERROR

ADDRESS
00100000

WRITE
0000

READ
1000

I am assuming this means it's a bad IC somewhere. How can I locate which one it is? Can it be replaced and if so, how? I really do not want to get a new mobo for this machine, as I have the memory card reader installed and all that good stuff. Any other ideas on what this could be, if not a bad chip? Thanks...

Dan
dan at bunnyears dot net
http://www.bunnyears.net
 

Razoola

Divine Hand of the UniBIOS,
Staff member
Joined
Nov 12, 2002
Posts
4,632
Before you start thinking about replacing ic's it could actually be a bad trace on the pcb to one of the ic's. As a first port of call I would advise giving the PCB a good clean.

Raz
 

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
OK. I have given it a half-hearted clean (compressed air etc), but have not pulled the board from the cabinet or disassembled anything. A friend strongly recommends putting boards in the dishwasher--he's done it in several of his classic arcade games--and says as long as you remove the things that would corrode (like, say, the metal bracket for cars on a Neo board) it works wonderfully--just chips and PCB come through wonderfully. Ever hear of that one?

Any better ideas on how to give the board a thorough cleaning?
 

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
Update: I ran the board through the dishwasher three times. I just hooked it up and the RAM error remains. Any advice? I have to assume now that it's a bad chip.
 

RiotoftheBlood

Chin's Drinking Partner
Joined
Jan 10, 2001
Posts
2,779
As Razoola said it could just be a bad trace. I think the next thing to do, especially since you already have the board out of your machine, is to spend a little time and look over it closely under plenty of light, paying the most attention to the visable traces. I would even consider using a magnifying glass. The washing will also probably help you see a litte better. If it's just a broken trace somewhere, that can be repaired much more easily than hunting for an IC, not mentioning hunting for a replacement.
 

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
Okay. A bad trace--you mean the actual pathways etched into the PCB? Can those be bridged with a piece of wire or something?
 

SuperGunGuru

Galford's Armourer
Joined
Jan 19, 2004
Posts
458
A good thing to invest in is a multimeter. I have one and it's invaluable to help troubleshoot games. It can tell you if a trace on a PCB is broken or not. I actually have a 4 slot pcb with a video ram error. It's got a major amount of scratches on the back, but I have yet to really mess with it since I've learned how to use a multimeter (I'm kina intimidated cause I may have to jump a lot of traces if the scratches did some damage. Maybe I'll get lucky, but at least I'll know where I stand). If you find a bad trace it can be bridged with a piece of wire. I usually just use wire to jump between the two points between the trace.
 

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
I am armed with a digital multimeter but I need to learn how to use it. So I guess that's step one, and maybe I can find the issue thataway. Thanks!
 

MKL

Basara's Blade Keeper
Joined
Mar 8, 2002
Posts
3,685
Digikey has a 32K x 8bit sram made by Windbond that should be a replacement for the old Toshiba TC55257 and Sony CXK58257 that you find on Neo hardware.

Digikey# W24257S-70LL T/R-ND

Hope someone can confirm this.
 

Dan Elektro

Morden's Lackey
Joined
May 22, 2001
Posts
363
So I still have the toasted MV-1 board but I bought another so I could be up and running again (thanks Dean). But I'd still like to get the original board repaired and keep it as a backup. I'm really not going to be able to change this chips myself; anybody interested in a little freelance engineering work?
 

stuffmonger

Baseball Star Hitter
Joined
Mar 9, 2005
Posts
1,254
Dan Elektro said:
So I still have the toasted MV-1 board but I bought another so I could be up and running again (thanks Dean). But I'd still like to get the original board repaired and keep it as a backup. I'm really not going to be able to change this chips myself; anybody interested in a little freelance engineering work?
I might give it a try... I have the hardware already to do it... I might even be able to burn you a unibios 2.0 ;) . Hows about this... I'll try to fix your mvs, and for compensation, I get to order an extra eprom for the unibios (about $6.50). I'll burn you a unibios 2.0, and install it if you have a board with an unsoldered bios (I still have a little difficulty with desoldering)... If i can't figure out how to fix your board, I'll still give you the unibios for your other mvs (unibios is better than stock bios), and I'll return the board back to you. I live in LA county, so if you feel like having me do this for you, I'm somewhat local, so shipping would be pretty cheap (or you could drive it to me).
 
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mainman

CPS2 Person.,
Joined
Mar 26, 2001
Posts
3,357
Dan Elektro said:
I am armed with a digital multimeter but I need to learn how to use it. So I guess that's step one, and maybe I can find the issue thataway. Thanks!

Ok is the fluke meter analog or digital. I going to assume its digital because you do not see those many analog meters. Ok on the meter depending on the type of meter you have turn the nob or push the button on to the symbol that looks like a sound wave. When you do that pick up the two lead that are coming out of your meter usually black and red and touch them together. They should buzz, this sound tells you that you have a electrical connection. This electrical connection can be a good thing when confirming none of your traces have been broken or a bad thing when you have a electrical conection ( short ) where there shouldn't be. Basically just follow the traces form point a to point b


Dan Elektro said:
So I still have the toasted MV-1 board but I bought another so I could be up and running again (thanks Dean). But I'd still like to get the original board repaired and keep it as a backup. I'm really not going to be able to change this chips myself; anybody interested in a little freelance engineering work?

Lucky you I currently have a surplus of the ram chip on hand and I am not busy right now so I do it for you for $20 providing you live in the U.S and pay for the shipping to and from me. I am a technician by trade surface mount no problem for me and I live in the south bay area of california which is local if you really live in California, U.S Also did you damage the board more in addition to the work ram error because that a bigger problem. Replacing the surface mount ram chips no problem, trouble shooting additional problem if you fried the board putting it in a dish washer is more work and I do not have time to trouble shoot the whole board. If problem is outside the ram issue I return the board along with 20 dollar fee.
 
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