Nichibutsu MagMax graphics issuse

[r67055]

hi!
I ran into an original magmax pcb. Can you help me with where to start troubleshooting? all eproms are fine, checksum. Thanks

 

[Hammy]

This is a bottom board fault i think... check the ribbon cables, (and also check the 4 small rams - 41464 / 2114 i maybe wrong on part number..)

 

[r67055]

4 pcs 2148 rams here

 

[r67055]

I replaced the 4 rams, the error remained. the error will surely be around 4 rams here. if I remove the ram, the character is missing from the monitor. I don't know how to find the error after this.

 

[Hammy]

Yes, that's the 4 rams, usually the problem.
I can see fuji 161's , check those next
Also check the rom tracks are good from the rom data lines (i think it goes from the roms > 157's maybe)
If the fuji's and tracks are good check the 157's

 

[r67055]

Yes, that's the 4 rams, usually the problem.
I can see fuji 161's , check those next
Also check the rom tracks are good from the rom data lines (i think it goes from the roms > 157's maybe)
If the fuji's and tracks are good check the 157's

8 pieces of 74ls157 and I tested it with a tester. no. none of them are at fault

 

[Hammy]

Nice one! Now check those fuji's 161's and 257's..
Now i see them it's probably the 257's

 

[r67055]

Nice one! Now check those fuji's 161's and 257's..
Now i see them it's probably the 257's

the 2 pieces are 257 and good. I continue tomorrow

 

[r67055]

the 2 pieces are 257 and good. I continue tomorrow

I tested 12pcs, 161s and they all work

 

[Hammy]

Damn, there's those 2x fuji 377 , after this it must be line damaged somewhere / bad contact

 

[r67055]

Damn, there's those 2x fuji 377 , after this it must be line damaged somewhere / bad contact

one of the 377 is faulty. I replaced it, but it didn't improve

 

[r67055]

one of the 377 is faulty. I replaced it, but it didn't improve

so much has changed that not all stripes are red

 

[Hammy]

Damn, looking better ... keep going through the other fuji's