Difference between revisions of "PCB Repair Logs Scramble Bootleg"
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'''Forum Thread:''' [http://www.aussiearcade.com.au/showthread.php/26459-Scramble-bootleg-MU1A-B-repair-log Scramble (Bootleg) PCB Repair]<br> | '''Forum Thread:''' [http://www.aussiearcade.com.au/showthread.php/26459-Scramble-bootleg-MU1A-B-repair-log Scramble (Bootleg) PCB Repair]<br> | ||
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Sterm schematic diagram matches up almost perfect. This one was a real challenge even with a schematic. | |||
Visual inspection revealed 3x D2125 rams with there tops smashed off and the M51516L audio chip smashed. | |||
Started off by removing the audio chip and socketing and replacing the damaged ram plus a general straighten up of squashed and bent legs on the solder side of the bottom pcb. | |||
Time for a smoke test disappointing no smoke or useful functionality just a screen full of floating diagonal coloured lines and no other signs of life. To cut a really long story short this was traced to a 74ls74 at 8N holding its clock input high stoping the vertical counters from counting. | |||
After replacing this the game now booted to a crosshatch pattern over a star field then reboot forever. | |||
Next verify program eproms ok remove and test all ram ok in fact everything looks and tests ok. After much frustration and hair tearing I found another 74ls74 at 9M with stuck inputs. Replacing this got the game booting correctly and could n ow be started and played except the shots from the craft were invisible. | |||
This was traced to yet another 74ls74 with a stuck clock input this time at 10L. Replacing this fixed the invisible shots. | |||
Now to replace the audio chip and test sound. This is when I found that M51516L chips are impossible to obtain. Anyway I ended up hacking in an MB3712 and sound now up and working well another classic saved from the scrap heap. | |||
Was it worth it? Most likely not but satisfaction of fixing it priceless. | |||
How long it will stay working for is another story considering there are more of those 74ls74s on the boards same brand and batch and they weren’t F chips. | |||
<br>[[PCB_Repair_Index|Back to PCB Repair Index]] | <br>[[PCB_Repair_Index|Back to PCB Repair Index]] | ||
Revision as of 08:34, 22 August 2012
Scramble (Bootleg)
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| PCB Image | Reserved |
|---|---|
| Pin Out | Reserved |
Repairer: truxpin
Forum Thread: Scramble (Bootleg) PCB Repair
Sterm schematic diagram matches up almost perfect. This one was a real challenge even with a schematic.
Visual inspection revealed 3x D2125 rams with there tops smashed off and the M51516L audio chip smashed.
Started off by removing the audio chip and socketing and replacing the damaged ram plus a general straighten up of squashed and bent legs on the solder side of the bottom pcb.
Time for a smoke test disappointing no smoke or useful functionality just a screen full of floating diagonal coloured lines and no other signs of life. To cut a really long story short this was traced to a 74ls74 at 8N holding its clock input high stoping the vertical counters from counting.
After replacing this the game now booted to a crosshatch pattern over a star field then reboot forever.
Next verify program eproms ok remove and test all ram ok in fact everything looks and tests ok. After much frustration and hair tearing I found another 74ls74 at 9M with stuck inputs. Replacing this got the game booting correctly and could n ow be started and played except the shots from the craft were invisible.
This was traced to yet another 74ls74 with a stuck clock input this time at 10L. Replacing this fixed the invisible shots.
Now to replace the audio chip and test sound. This is when I found that M51516L chips are impossible to obtain. Anyway I ended up hacking in an MB3712 and sound now up and working well another classic saved from the scrap heap.
Was it worth it? Most likely not but satisfaction of fixing it priceless.
How long it will stay working for is another story considering there are more of those 74ls74s on the boards same brand and batch and they weren’t F chips.
