RASTAN repair help needed

obitus1990 · Feb 16, 2023

Sorry for the somewhat crappy picture, which is a capture of a video (on a bad monitor) sent to me by the board's seller prior to my purchasing the PCB - I did not notice this until I received it and observed this graphic problem in person.

If you look at Rastan's boots, you can see that they have vertical stripes, alternating pink and red. And if you look more closely, you can see vertical bars running through Rastan himself and his throne.
The candy-striped boots are also seen on the "continue" screen and after beating a level. It's way more noticeable in person versus what this photo shows. I don't notice any other areas of the game having these color/banding issues. I have another 100% working Rastan board, and, have also checked the game in MAME, and his boots are solid red. If I had not obtained a second 100% working one, I wouldn't have thought anything about it, because the game is otherwise perfectly playable and seems to function normally. Where on the board should I be looking to try and fix this?

Thanks!

Pythagoras · Feb 16, 2023

Since the problems are limited to such small areas. I suggest that you start with dumping and verifying the program roms and the graphics roms.

Have a look at Mames Rastan driver. The tile map and palette data for the screens you are describing are located in the two last program roms. the tile grapics are in the "pc080sn" maskroms.

there are severals revisions and regions of the game. But if I take the newer US region set as an example, I would start with the following roms:

"main cpu"
"b04-42.21"
"b04-41-1.9"

"pc080sn"
"b04-01.40"
"b04-02.67"
"b04-03.39"
"b04-04.66"

obitus1990 · Feb 17, 2023

Thank you! I'll dump them this weekend when I get the chance. If it happens to be a bad mask ROM, are those, do I use a 27C512 EPROM as a replacement?

Pythagoras · Feb 17, 2023

No you can not use a 27C512...

From Jammarcade's Rastan repair log

"...The gfx ROMs on this board are 128kb fitted into 28 pins chips. Finding blank chips with these exact specs is hard nowadays so I used 128kb 32 pins 27C010/27C1001 EPROMs as replacement (I could use a 27C1000/27C301 EPROM to make the modification even easier"

"If you use a 27C301 or 27C1000 non-JEDEC EPROM (simplest way):

Connect pins #30, 31, 32 together and connect them to pin #1 with a small wire.
Connect pin #2 to pin #16 with a small wire.

If you use a 27C010 or 27C1001 JEDEC EPROM:

Connect pins #30, 31, 32 together and connect them to pin #1 with a small wire.
Gently bend pin #24 so it won’t plug into the socket and connect it to pin #16 with a small wire.
Solder a small wire on pin #2 that you will plug into pin #22 of the socket."

Another alternative is to buy this preprogrammed 28 pin 1Mbit Mask ROM replacement

obitus1990 · Feb 25, 2023

Today, I swapped out the mask ROMs as indicated in the Mame drivers. It didn’t fix the problem, nor did swapping the program ROMs that controlled this part of the graphics.

BUT…it was a mask rom problem….just not how you’d expect it.

Take a look at how beat up the edge of the socket is. Someone went nuts with a screwdriver removing ROMs here, gouging up the socket, and cutting a trace. The PCB was gouged into the underlying fiberglass. Cleaned things with IPA, then took out my most hated tool, the scratch brush, exposed some copper and did a very amateur trace repair with 30 guage wire.