Gyruss PCB Problem: Bad Character ROM?

Possibly. You'd have to verify the contents of the eproms to see if they're all still good. More likely its video ram. But verifying the program contents is a good place to start....
 
Looks familiar. Had the same problem. Fixed mine by replacing the Ram chips @ 7A and 7B on the large board. 2149 rams I believe.
 
# this document is not going to be of much use to you unless you have
# the schematics and follow along.

# Gyruss ROM files from TANT archive
GYA-1.BIN - 11J - CPU Z80, 8K, Addr 0000 - 1FFF
GYA-2.BIN - 12J - CPU Z80, 8K, Addr 2000 - 3FFF
GYA-3.BIN - 13J - CPU Z80, 8K, Addr 4000 - 5FFF
GY-5.BIN - 18E - CPU 6809, 8K, Addr 0000 - 1FFF
GY-6.BIN - 02H - Graphics ROM
GY-7.BIN - 5B/6C - Graphics ROM, 8K Bank 1, MSB
GY-8.BIN - 6B/7C - Graphics ROM, 8K Bank 0, MSB
GY-9.BIN - 7B/8C - Graphics ROM, 8K Bank 1, LSB
GY-10.BIN - 8B/9C - Graphics ROM, 8K Bank 0, LSB
GY-11.BIN - 6A - Audio Z80, 8K, Addr 0000-1FFF
GY-12.BIN - 8A - Audio Z80, 8K, Addr 2000-3FFF
GY-13.BIN - 11H - Audio 8039, 4K, Addr 0000 - 0FFF

# Gyruss CPU board memory map, gleaned from the schematics ...
#

#Addr Chip Loc Romfile? Description
#-------- ---- ---- ---------- -----------
0000-1FFF 2164 11J GYA-1.BIN 8k EPROM
2000-3FFF 2164 12J GYA-2.BIN 8k EPROM
4000-5FFF 2164 13J GYA-3.BIN 8k EPROM
6000-7FFF 2164 14J N/C 8k EPROM
8000-87FF 2128 17C 2KB RAM, shared w/6809
8800-8FFF aliased ram
9000-9800 2128 5J,3J,2J 6KB SRAM
A000
B000
C000
D000
E000
F000

#
# CPU Board custom "6809"
#
0000 \_ /VCOUNT = 0, R/O places contents of 819:825 on data bus
1000 /
2000 \_ /9IRQ = 0
3000 /
4000 \_ SRAM @ 14A,13A,12A,11A MUXED with sprite generator. Even / Odd
5000 / Data is split between X and Y; X related to cols, Y related to rows
6000 \_ /9ZRAM -- Accesses 2K shared memory between Z80 and 6809
7000 /
8000 \
9000 |
A000 \ _ Not mapped.
B000 /
C000 |
D000 /
E000 \_ Program ROM, 8k 2764 (E000 - FFFF)
F000 /


Not having the board in front of me, I would probably be inclined to start by checking the SRAMS at 11-14A first, replace them if you can, and work backwards through the TTLs between them and the CPU if replacement does not fix.

Not much going on on this board, a few minutes with a logic probe may find a stuck input or output / shot TTL on the board. I'm finding this increasingly common these days. Good news is that it boots and doesn't watchdog. This takes a lot of stuff off the suspect list. And likely means it's not the shared SRAM or main program RAM.
 
I have seen more logic problems than memory on gyruss boards I have fixed in the past. They used alot of fujistu chips and they dont seem to hold up as well as others.
 
I pulled a couple of chips out today that had a rainbow-esque tarnish on them. I cleaned them all up, reseated and was able to get some additional graphics (continents from the globe on the title screen). I will hopefully have time next week to probe these.
 
I had one once that was working perfect except the continent was missing. The problem was a bad ttl chip. Do you have a burner so you can verify the roms?
 
I had one once that was working perfect except the continent was missing. The problem was a bad ttl chip. Do you have a burner so you can verify the roms?

I don't, I may ask one of the local guys if they can help out on this.

This poor Gyruss has seen better days.
 
I just fixed 3 sets of gyruss boards this evening. One set had this same issue among a couple others. I started with just a white snowy screen, nothing was visible. I replaced one of the 2149 rams and it brought up some blocks where the moving sprites should be. I now had a grey screen and no color at all. Tracked the problem back to a bad color prom. Replaced and the background was there and in full color but the moving sprites were still grey blocks. Traced it back and found a second bad color prom. This brought the colors back but the graphics were still a little off....the second 2149 was bad! My guess is a ram went out and took out everything with it.
The board also had a problem where it would constantly coin up and start a game on its own. This was easy to find, a bad 367 @ 2B.
Ok enough rambling, I would try swapping out the 2149 rams first. There is also at least one custom that will cause the same issue but the 2149 rams are more likely the problem.
 
Back
Top Bottom