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Ravepants

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Hi All,

I have a naomi 2 that was recently recapped it was working fine up until recently when it started booting to a black screen (with a cart or netdimm/pi)

I read in one of tylerdurdans posts that it could possibly be a corrupt BIOS, so I got a new one (multi, new 2020 version patched for atomiswave) and i still got the black screen.

I did the usual voltage tests (all spot on) re-seated the bios chip, made sure the on board battery is still good, but still nothing, in a fit of desperation i tried flipping the 15/31k switch on the filter board to 15k, when i booted up it sprang into life! to test a theory i booted it again an it still worked, then i flipped it back to 31 and rebooted and it came to life again in 31k!

This seems to be intermittent, as i left it on to soak test for about 3 hours and when i returned to it, I had a black screen again, but when i flipped it back to 15k and soak tested it was still on about 4 hours later.

Any one have any idea where i can even begin to look at what might be causing this? my instinct says maybe video encoder or whatever part of the circuit deals with the 15/31k switch, maybe one of the GPU's? i'm stumped!
 

Ravepants

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Is there anyone in the UK/Europe that might be able to take a look at/diagnose my N2?
 

MetalliC

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I read in one of tylerdurdans posts that it could possibly be a corrupt BIOS, so I got a new one (multi, new 2020 version patched for atomiswave) and i still got the black screen.
on a side note - in such case better use older multi, it will never "black screen", becase of protection bypass, as well as it will still work if burned to some not good EEPROM which will have some "bad bytes".
newer multi require 100% matched ROM, just like original BIOSes, otherwise it will boot to blask screen due to protection.

as of issue - sounds like crackled PCB or GPU connections or smth else like that
 
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CoolFox

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Open up the Naomi and look for the two 315-6145s. See if one of them is hot or even warm while it's on. They should be cold. If one if em is hot, remove that one and replace it with the other one, the second one isn't used and it's basically an extra part.
 

MetalliC

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the second one isn't used and it's basically an extra part.
that's not true for Naomi 2 games, both of video coder ICs works in the same time and output video signals, and later mixed together by Altera MAX CPLD (which might be a problem too)

in any case, if there is problem with DACs or related circuits - games should still work normally and there should be sound from BIOS logo and games but just no picture. @Ravepants is this correct ?
 

Ravepants

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@MetalliC I'll have to double check the BIOS makes audio output and report back, i honestly can't remember since i last fired it up.

I'll take a look at the 315-6145 and Altera as also (well as best i can)
 
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