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Hackcell

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My outrun board is not booting up, and after some troubleshooting and checking online, there is a HIGH possibility that the problem is related to the 2015ap SRAMs. After checking digikey, I couldn't find an exact replacement, closest was 15ns when the original is 90ns.

Having said that, is it safe to install faster RAM modules, shall I replace all SRAMs to match the speed or a 15ns SRAM won't work at all?

Thanks in advance.
 

bytestorm

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My outrun board is not booting up, and after some troubleshooting and checking online, there is a HIGH possibility that the problem is related to the 2015ap SRAMs. After checking digikey, I couldn't find an exact replacement, closest was 15ns when the original is 90ns.

Having said that, is it safe to install faster RAM modules, shall I replace all SRAMs to match the speed or a 15ns SRAM won't work at all?

Thanks in advance.
Dont shotgun, use this memory diagnostics, its VERY helpful to check the rams: http://www.aaldert.com/outrun/memtest.html
You just need 4x 27C512 eproms/flash to test your board, and all other roms can be left in their sockets.

If used with Turbo OutRun you also need to change the special encapsulated 68000 into a regular 68000 to get the board to boot the test.
 
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bytestorm

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Is it not booting with the memorytest roms? Or did you not try them? Are you using a supergun? It's a powerhungry board.. does the diodes turn on showing you actually have powered the board?

Give some more details and it's easier to help you
 

Apocalypse

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Is it not booting with the memorytest roms?
Never tried those ROMs (and I repair OutRun boards every week), are they supposed to boot even with all work RAMs dead?
RAM is only one cause for problems amongst many others.
It's a powerhungry board.. does the diodes turn on showing you actually have powered the board?
Definitely power hungry, my 15A PSU is at its limit!
Like all Sega boards from that era, the diode is simply tied to Vcc through a resistor. It's only a rough indication that power is present (but can't tell if you're at 4,5 or 5,5) and isn't related to any function of the board.
 

bytestorm

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Is it not booting with the memorytest roms?
Never tried those ROMs (and I repair OutRun boards every week), are they supposed to boot even with all work RAMs dead?RAM is only one cause for problems amongst many others.
It's a powerhungry board.. does the diodes turn on showing you actually have powered the board?
Definitely power hungry, my 15A PSU is at its limit!Like all Sega boards from that era, the diode is simply tied to Vcc through a resistor. It's only a rough indication that power is present (but can't tell if you're at 4,5 or 5,5) and isn't related to any function of the board.
No, of course if all workrams were to be dead that would be difficult, but the author wrote this on the webpage:


No display?
The tests will blink the START (A21) lamp for every good RAM it finds, and blink the BRAKE (A22) lamp for every bad one. You can hook up LEDs with 330Ω series resistors to still have crude diagnostics. Please note that the digital in/out port also requires external power and ground hooked up in order to work.



And about that diode, yeah, its only a rough indicator, but atleast youll see something.

Best is by far to just measure the voltage over some known components away from the connector, to get a true reading.
 

Apocalypse

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No display?
The tests will blink the START (A21) lamp for every good RAM it finds, and blink the BRAKE (A22) lamp for every bad one. You can hook up LEDs with 330Ω series resistors to still have crude diagnostics. Please note that the digital in/out port also requires external power and ground hooked up in order to work.
That's actually clever.
But RAMs are only one part of the puzzle, and it's quick enough for me to rule them out not to bother burning diag ROMs.
 

bytestorm

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No display?
The tests will blink the START (A21) lamp for every good RAM it finds, and blink the BRAKE (A22) lamp for every bad one. You can hook up LEDs with 330Ω series resistors to still have crude diagnostics. Please note that the digital in/out port also requires external power and ground hooked up in order to work.
That's actually clever.But RAMs are only one part of the puzzle, and it's quick enough for me to rule them out not to bother burning diag ROMs.
Yeah and the ROM tests dosnt seem to work as I have changed several maskroms on the video pcb side that has been bad. (maybe they arent tested?)
CPU pcb is easier to troubleshoot, but for the lower video pcb it has saved me quite some time :). But also had some pals fail on the bottom pcb.
 
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