MVS MV1T VRAM error help identify chip (resolved)

Joined
Apr 2, 2020
Posts
8
Hi everyone,

I have an MVS MV1T that all of the sudden started developing bad patches of graphics on backgrounds and such (not sure if character sprites as well?).

I get the following
VRAM DATA (0000)
Address 000E13

screen but I am not sure which ram module physically it is on the board that is not working to replace.

Thank-you!
IMG_20200329_223553736.jpgIMG_20200329_225137841.jpgIMG_20200423_101638023.jpg
 
Last edited:
Joined
Apr 2, 2020
Posts
8
I tried reflowing the legs of the chips at G3 and G4 and no luck. I will try to find some replacement chips then (looks like ebay - from hong kong or china... :/).

Thank you shadownkn55.
 

HeavyMachineGoob

My poontang misses Lenn Yang's wang
10 Year Member
Joined
Apr 3, 2011
Posts
5,790
Uh, there's only two chips for Video RAM though. The others are x2 Work RAM and x2 Backup RAM. All are plain old 256Kbit Static RAM chips used for different jobs.
 

shadowkn55

Genbu's Turtle Keeper
15 Year Member
Joined
Dec 9, 2006
Posts
2,386
Uh, there's only two chips for Video RAM though. The others are x2 Work RAM and x2 Backup RAM. All are plain old 256Kbit Static RAM chips used for different jobs.

There are actually 4. 2x 256kb and 2x 16kb. He was probably referring to the possibility that the other 256kb srams need to be replaced as well.
 
Joined
Apr 2, 2020
Posts
8
Thanks everyone. I wanted to buy a few extra in case the others decide error as well. Although I will probably use replace the 2 faulty ones first to see. I used to think these old arcade/console hardware were indestructible, then my snes started glitching, then learned about capacitors leaking, then batteries leaking, then RAM issues with MVS (from not even that much use).

I just ordered 6 from Digi-Key.
 
Last edited:

shadowkn55

Genbu's Turtle Keeper
15 Year Member
Joined
Dec 9, 2006
Posts
2,386
I need to make a correction. VRAM is at locations G4/H4. Work RAM is G3/H3. Backup RAM is H5/H6
 
Joined
Apr 2, 2020
Posts
8
I got the replacement RAM chips from Digikey today and tried to desolder each leg and lift but ended up giving up. I ordered some Chip Quik smd low temp solder to do this. I am not comfortable with hot air stations.
 

shadowkn55

Genbu's Turtle Keeper
15 Year Member
Joined
Dec 9, 2006
Posts
2,386
What I like to do if you don't have fancy tools is snip the legs off of each of the four corners and then apply solder to remove the legs. Keep doing this until all the legs are removed and the chip should have nothing holding it to the board. Then use solder wick to remove the excess solder. Clean the area with flux remover and solder on the new ram. This should be done with a chisel tip especially when using solder wick.
 
Joined
Apr 2, 2020
Posts
8
Success! Thank you shadowkn55!

I followed your tip and snipped the 4 legs at the corner and slowly lifted the other legs. I replaced only the 2 chips at G4 and H4, but have enough spares for the others. All the tests passed and even my normally static sounding Windjammers is now like 99% no static (maybe the volume might be too loud the other 1%). No more graphic glitches. I would have never figured out which chips were the vram without your help.

I am running the mvs board through a supergun manufactured by retroelectronik v1 and using a pc power supply, the voltage meter onbard said it is 5.12 v. Would that have been enough to have harmed the RAM originally or the board overall? I do use other jamma boards on this setup as well and don't want to fry components.IMG_20200430_161748033.jpgIMG_20200430_162216670.jpg
 
Last edited:

shadowkn55

Genbu's Turtle Keeper
15 Year Member
Joined
Dec 9, 2006
Posts
2,386
What I meant was snip the corners, remove, and rinse/repeat with the "new" corners. I don't like lifting legs if I can avoid it. But at least you got it done without lifting any pads.
 
Joined
Apr 2, 2020
Posts
8
My wire snipper's tip was not fine enough to get the inner pins so I used a dental pick and soldering iron to slowly lift each leg. Thankfully I didn't lift any pads or traces.
 
Top