TRON Graphics Issue

KI4SWY

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Donor 5 years: 2013, 2020-2023
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[Solved] TRON Graphics Issue

I have a tron boardset I am working on, and trying to determine what could be the problem before i start ripping every ic off, and replacing..

What i have checked:

1) All roms pass verify with tron set from mame.
2) All rams chips test ok (i swapped them all around with no issues, and even did test dip switches)
3) any logic chip that was socketed that could be swapped with same chip, swapped. (ie, 74ls244 for a 74ls244)

I am thinking possibility of one of the 3 74ls157 on the graphics board.

The MCP Cone is jacked up, and the tanks got grid bugs on them. its almost like its picking the wrong sprites?

Video: http://www.youtube.com/watch?v=lzpWu1G_Oaw
 
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its being powered on the bench with a switcher, the power is set to 5v on the logic rail, and 12v .

also, has new ribbon cables, not crappy scsi cables or original oem cables.

well, its either N3, or the 2to1mux chips, going to fire up the 32ch logic analyer, and validate proper operation.
 
Im no to this kind of work..learning slowly..have a scope and meter..
Is there a test point I should look for for clock pulse...
still reading circuits.

I have order new Vram chips also.. see what i get.

I have older cables, original power supply...buzzed out and all test fine.

i cant run diagnostics test ast I cant see the cursor !!

GRRRR!!!!
 
i had two bad object ram chips. (swapping two bad chips gave same result)

i needed up swapping all 4 from the object ram, to the other section, and graphics were fixed, but then had symptoms of dots uniform acros screen...
 
Just an FYI, make sure the freeplay chip software matches the date of the other EPROMS. There are 3 variations and can cause issues if they don't match.
 
here is what happened when i swapped my object ram for my other ram.

(there are 8 sram chips on the graphics board, if you swap them around, and you will notice a pattern on the display (i zoomed it on the pattern, and then pointed to which rams cuase that))

http://www.youtube.com/watch?v=Fh7f8xpDn2s
 
I would like to thanks those who posted.. Problem fixed, machine back together
 
bad object ram.

but have other issue now, score resets to 5k when i get 10k , and there is no orange, so will be putting back on bench to fix those issues.. (the orange is mostlying bad resister, or maybe transister, or the sram chip on the cpu board is toast.
 
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