- Thread starter sega_man
- Start date
All the RAM is back in and all of the logic LS chips, the test still fails all of the RAM & the two customs!
My logic probe hasn't arrived yet (useless seller took nearly a week to even dispatch it!).
Slightly disheartened to not even get the RAM working as that was all OK when I first replaced it. I've checked each pin is joined on the RAM to each other and it is now, so can only be a track or tracks that go on elsewhere, possible why the customs fail too?
Any idea's anyone? Or which chips to probe (with expected results?) when the probe arrived?
My logic probe hasn't arrived yet (useless seller took nearly a week to even dispatch it!).
Slightly disheartened to not even get the RAM working as that was all OK when I first replaced it. I've checked each pin is joined on the RAM to each other and it is now, so can only be a track or tracks that go on elsewhere, possible why the customs fail too?
Any idea's anyone? Or which chips to probe (with expected results?) when the probe arrived?
This is what I've found : -
RAM pin (I've checked all the pins marked A on the data sheet, address lines?)
2 > A4 X
3 > A5 > IC33 pin 2 (A1)
4 > A6 > IC36 pin 16 (B2)
5 > A7 X
6 > A8 > IC34 pin 8 (A7)
7 > A9 > IC36 pin 9 (A7)
8 > A10 > IC34 pin 8 (A7)
9 > A11 > IC36 pin 5 (A3)
10 > A12 > IC34 pin 17 (B2)
21 > A0 > IC33 pin 13 (B6)
23 > A1 > IC35 pin 9 (A7)
24 > A2 X
25 > 3 > IC33 pin 17 (B2)
So at a guess issues with pin 2, 5 & 24 on the RAM? I wish I had a schematic I could make out...or another board to check against!
RAM pin (I've checked all the pins marked A on the data sheet, address lines?)
2 > A4 X
3 > A5 > IC33 pin 2 (A1)
4 > A6 > IC36 pin 16 (B2)
5 > A7 X
6 > A8 > IC34 pin 8 (A7)
7 > A9 > IC36 pin 9 (A7)
8 > A10 > IC34 pin 8 (A7)
9 > A11 > IC36 pin 5 (A3)
10 > A12 > IC34 pin 17 (B2)
21 > A0 > IC33 pin 13 (B6)
23 > A1 > IC35 pin 9 (A7)
24 > A2 X
25 > 3 > IC33 pin 17 (B2)
So at a guess issues with pin 2, 5 & 24 on the RAM? I wish I had a schematic I could make out...or another board to check against!
Think it may be time to give up 
Ken from irepairsega said.....
"It most likely will not help with prints or another pcb. I have repaired hundreds of these in the long gone past and no(sic) how they go. Its easier to find replacement pcb."
Bugger. I hate giving up and really think anything can be fixed! I know the chip is good. It can only be another chip elsewhere or bad track!!
A decent schematic or a working board seems the only way?.....
Ken from irepairsega said.....
"It most likely will not help with prints or another pcb. I have repaired hundreds of these in the long gone past and no(sic) how they go. Its easier to find replacement pcb."
Bugger. I hate giving up and really think anything can be fixed! I know the chip is good. It can only be another chip elsewhere or bad track!!
A decent schematic or a working board seems the only way?.....
Gamesmonkey
Enthusiast
I always find its a bit of a roller coaster fixing pcbs. Give it a couple of days and take a fresh look at it.
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I found an Afterburner PCB which is marked as "bad input". Hopefully it can assist with fixing mine. One thing though, the PCB doesn't have the connector for the extra sound board. Is that connector available?! Doesn't look like it would come off my board easily...
OK, Afterburner Arrived 
I forgot about import duty 
The game booted up with minor screen glitches on the text......
I inserted the test ROM's & got this : -
Not those RAMs AGAIN!! I've socketed them all, swapped them for all new chips & get the same result, even swapped the RAM out of IC22 to one of the others doesn't change the test so it can't be the RAM, so what CAN it be?
IC133 is also reporting an error, I'll get sockets for that later, at the moment I just want to clear this RAM error!! The games own self test reports the same for IC133 : -
At least the game boots! I haven't tried swapping all of the ROMs to Super Monaco yet. The sticker on the board actually said "2 bad inputs in pull up rework"....
I forgot about import duty The game booted up with minor screen glitches on the text......I inserted the test ROM's & got this : -
Not those RAMs AGAIN!! I've socketed them all, swapped them for all new chips & get the same result, even swapped the RAM out of IC22 to one of the others doesn't change the test so it can't be the RAM, so what CAN it be?
IC133 is also reporting an error, I'll get sockets for that later, at the moment I just want to clear this RAM error!! The games own self test reports the same for IC133 : -
At least the game boots! I haven't tried swapping all of the ROMs to Super Monaco yet. The sticker on the board actually said "2 bad inputs in pull up rework"....
Mrhide
Enlightened
from: https://github.com/djyt/xboard_memtest/blob/master/src/main.s
_memtest_ab_local:
CALL memTestAddressBusAsm
_memtest_ab_done:
AB= Address Bus
_memtest_dev_local:
CALL memTestDeviceAsm
_memtest_dev_done:
Dev = Device
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Ok. Some more progress. RAM was fine, it was IC36 causing the issue. IC133 is still reporting bad even though it's been swapped for a known good chip. Another logic chip failure...but which one?! Original board is still giving grief. I've swapped all of the RAM and logic chips in that area but no change. Whats interesting is the new board reported custom ICs as bad when more than one of the logic ICs was also bad.
Indeed. Hard working people deserve respect!
No errors, at last! Found a single line on IC132 (even though IC133 was reported as bad!) was dead to the LS chip.....
Now to get the SMGP ROM's in and the sound board. Something tells me this won't be the end but at least it's progress! I'm hoping I can use the good board to then fix the original (full of errors!) board!
Now to get the SMGP ROM's in and the sound board. Something tells me this won't be the end but at least it's progress! I'm hoping I can use the good board to then fix the original (full of errors!) board!
RedFighter
Student
Congrats 
RedFighter
Student
Hi,
did you exchange the 5 PAL ICs?
IC 18 - 84 - 109 - 117 - 127
I don't know by heart whether all 5 are different from the game Afterburner, it's best if you swap them all out.
did you exchange the 5 PAL ICs?
IC 18 - 84 - 109 - 117 - 127
I don't know by heart whether all 5 are different from the game Afterburner, it's best if you swap them all out.
