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Naomi 1 no video or audio, schematics would be very helpful...

Papalati

Papalati

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I got a Naomi 1 that was in an 18 Wheeler that I picked up. There was a note on the Naomi housing that said something about it won't boot until it gets about 5.7V which is obviously not good. The owner said it would still work, but aside from the high voltage to get it to boot he said the game had occasional freezing and/or looping. I obviously didn't try it onsite to risk any further damage.

When I first booted it, it powered on, but no video or audio. So, I then checked traces and when everything looked fine I then completely recapped. After the recap I found a short to ground near 315-6145 that was causing a short on pin 40 of said chip, but I found and resolved this issue. But still no video or audio.

Before I continue with a guessing game and testing each and every component I wanted to ask if anyone had ever seen or has the board schematics for the Naomi 1.
 
the pins of a 27c160 and a 29f160 are almost identical
besides, your point of interest is the RAMDAC.
 
incidentally, did you check for 3.3v at the main chips??

the system monitors the gpu fan and if it's not spinning fast enough it cuts power to the main chips to prevent gpu failure
 
Yeah the main chips all have 3.3 but they just don't feel like they are getting warm. The only reason I was asking about the pinouts for the bios is that on certain pins I had no readout but then after recapping and reflowing the board I was able to restore most of the pins that had no readouts before. The numbers in red are the pins that were reading 0 and are now reading correctly. But the numbers in blue are what the pins should read but they are currently reading 0.

IMG_2301.jpg


As for the ramdac, I was also thinking the ramdac since the previous owner mentioned overvoltage to the board to get it to run. But since I started restoring readings to the pinouts I wanted to verify it wasn't something else first.

Is the RAMDAC the 315-6145 chip? Cause I got a weird short to ground that runs along a trace to 3 caps that are shorting to ground on positive. But when I checked a working Naomi, it had the same short to ground output but works fine.
 
315-6145 (VA0, Early VA1, Naomi 1) ROHM BU1426KS
315-6258 (Later VA1, VA2.1, Naomi 2, Atomiswave) ROHM BU1428KS
 
btw, bad RAMDAC's often get very hot.
but check your filter board too - i had a few with burned traces to the vga connector - cause unknown
 
Filter board is fine since it works with the other Naomi just fine.

I’ll transfer the working ramdac to the other one and see what happens.
 
stj said:
btw, bad RAMDAC's often get very hot.
but check your filter board too - i had a few with burned traces to the vga connector - cause unknown
Click to expand...

so after swapping the ramdac nothing happened. same result. no audio, no video.

is the super capacitor required to boot? I didn't think it was since it was missing when I bought the arcade. Figured the vendor just ran it without one and this is the first one I've had to work on.
 
TheDeath said:
Have a read at this: https://www.arcade-projects.com/threads/repair-log-sega-naomi.456/
Click to expand...
Thanks for the clues.

Installed a working super cap from a working Naomi in place and now I get some hum from the speakers. But that's it.

Bios chip is good as it works fine in another Naomi.
GPU fan spins fine.
All pins have continuity for EEPROM (IC31) -> Altera (IC30)

The only one that I cannot figure out is - "Fixed CPU had more particularly to the BGA (rare as on the N1)" the statement makes no sense to me.

None of the ICs are getting warm and yet they are getting 5v and 3.3v on various pins.

I'm ready to pull my hair out.
 
PAPALATI said:
I'm ready to pull my hair out.
Click to expand...

If changing the rams didn't work, than you got yourself a wonderful door-stopper.
That statement meant reballing the CPU, it's BGA (ball grid array). I've tryed myself and it never worked with common tools, you got to have an expensive reballing station. When that happens i usually toss them in the bin. I was however able to revive many of these Naomis using that guide. I personally also change all the 8x rams near the cpu with new ones, they are easy to find on aliexpress
 
you dont need the supercap,
it's just backup for the coincell
 
TheDeath said:
If changing the rams didn't work, than you got yourself a wonderful door-stopper.
That statement meant reballing the CPU, it's BGA (ball grid array). I've tryed myself and it never worked with common tools, you got to have an expensive reballing station. When that happens i usually toss them in the bin. I was however able to revive many of these Naomis using that guide. I personally also change all the 8x rams near the cpu with new ones, they are easy to find on aliexpress
Click to expand...
Yeah, I don't see any physical issues with the board. All the chips are receiving 5 and 3.3v but they just aren't getting warm. And the 2 heatsinks aren't getting warm either. The board acts like it should be on, but nothings happening. Full recap and full reflow and still nothing. After replacing the super cap I got hum in the speakers again as if they were gonna turn on, but that's all. So yeah, all I could think of was either the gpu or the cpu at this point. Depending on the amount of the bga needing reballing I do have the tools to do it. Also helps if there is a stencil for it.

I'll order some ram since I have more than 1 of these with an issue.
 
maybe the clocks are missing - bad crystal or oscillator?
 
I finally have a positive update. After pouring over the board component to component I found that a dummy resistor was missing at R269 and so I just moved one from the working one I had and suddenly I had video once again. It sounds like there should be sound, but I'm not getting the Naomi jingle at startup. So, now I'm on to figuring that part out now.
 
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