MV-1F Video RAM Error

[daskrabs]

Bad RAM chip or trace? or something else?

 

[Xian Xi]

Check the upper video ram, looks to be missing control signals. WE, CE and OE.

 

[daskrabs]

Check the upper video ram, looks to be missing control signals. WE, CE and OE.

Not sure which chip that is.

 

[xsq]

There should be two chips labeled Sony CXK5814P-35L, it's one of those.

 

[mjs256]

There should be two chips labeled Sony CXK5814P-35L, it's one of those.

Yes, it is one of the CXK5814P-35L chips - they are the fast video RAM. In my experience it is almost always a bad chip and not a bad trace with these. From the error message it looks like only one of the two is bad.

 

[daskrabs]

Chip ordered.

 

[xsq]

I'd recommend to solder a socket in there. These chips don't take to heat too good and sometimes the replacement you get might be bad, so having a socket will safe you some worries.

 

[mr_e]

I'd recommend to solder a socket in there. These chips don't take to heat too good and sometimes the replacement you get might be bad, so having a socket will safe you some worries.

Aren't the ram chips surface mount?

 

[shadowkn55]

Aren't the ram chips surface mount?

The 35ns video ram chips are all DIP. Most of the other ram are generally SMT.

 

[sonix]

I have this error video ram error address 00008000 write 5555 read 0000. I replaced the both chips and nothing has changed. Does anyone has an solution.

 

[Xian Xi]

You have to check the control lines since the read says 0000. That means it's not getting any control signals.

 

[Asure]

Take some pictures of the general area around the new chips you installed.. maybe some traces cracked..

 

[sonix]

I've checked the traces already on top and bottom with a multimeter. The problem occurred when i accidentally plugged the jamma harness in with power on. Isn't there a fuse that coould be blown?

 

[Asure]

There are no fuses on any MVS motherboard. There _is_ lots of 74LS logic chips (and flatpack integrated versions of these) that do not like the massive voltage spike/inrush you gave them. You need a logic probe and some basic understanding of electronics to fix this.

Also you need to post much, much more details about this problem. We're not wizards. No crystal ball..
So we need to know which version mainboard, how many slots, how it happened (three posts later you tell us you fucked up.. etc.) And when someone asks for pictures, it's not just to see broken traces, we could have known the motherboard by now and instead i'm wasting time typing this post asking you _again_.

Anyway, you can do some tests on the rams and see if anything changes. But the 0000 read, that's a bad sign.

See http://forum.arcadeotaku.com/viewtopic.php?f=46&t=24021 for my repair log.

 

[sonix]

It is an mv-1f.

 

[Xian Xi]

Check pins 18, 20 and 21. 18 and 20 are grounded and 21 is connected to the LSPC2(86?).

 

[Xian Xi]

Also, you sure you didn't damage any of the connections when removing the old chips? If you desoldered everything right then it should be working after you replaced both chips.

 

[sonix]

pins 18 and 20 are grounded on both chip and 21 has good connection on pin86. I'm affraid that something els has fried. I also checked if the chips have power and ground those are ok also.