[Repair Log] Naomi 2 won't boot

[doccaz]

Hi all,

I acquired a Naomi 2 at a japanese auction, and besides some heat marks and scratches on the plastic case, appears to have been untouched. Even the screws had that "factory torque" when I opened them.

I inspected the motherboard on the microscope and found no corrosion at all. All capacitors appear (visually) to be okay. The only issue I could find was that the wires to the middle GPU fan were "chewed up" pressed between the edge of the case. But they all checked out okay with a continuity test, just added some tape to them. Looks like someone at the factory was in a hurry and didn't wait for the hot glue to cool down.

I got an ATX PSU adapter from China, and plugged it to a brand-new Coolermaster PSU. The voltages are spot-on (5.1v and 12.1v).

When I powered it on, both the red and green LEDs lighted up, and both GPU fans spinned as expected. The case fan was loud and mostly stuck, so I exchanged it for a new one.

Plugging a VGA monitor shows no signal detected (tried two different monitors). I tried changing the first dip switch to OFF as well (this was installed on a cabinet with a CRT?).

I replaced the IC29 super-cap with one of the same value (5.5v 0.1uF, which took ages to arrive...), and still no screen.

I re-seated the BIOS chip as well. It's marked EPR A-23605.

I read some of the threads mentioning that there could be a burnt ground trace on the connector board. Mine is spotless.

Any suggestions? I'm new to the Naomi hardware, any help will be appreciated.

 

[doccaz]

Measuring the voltage test points on the motherboard:

- 3.5V (in the middle of the board): 3.459V
- 3.3V (in the corner of the board): 3.308V
- SH4_V: 1.935V
- 12V: 12.000v (really!)

Nothing appears to be getting warm.

 

[doccaz]

I also checked that the fan speed wires are pulsing with the oscilloscope. They are. One is pulsing at 670khz, the other at 570khz.

Does the Naomi have a serial port or a serial console of some sort?

 

[doccaz]

BTW, on the NetDimm (which I didn't plug in yet), I see that there is a SCSI port, LAN port and a DB-9 connector. Is that a serial port, or what is it used for?

 

[ShootTheCore]

A few ideas based on the Naomi troubleshooting thread here:
https://www.arcade-projects.com/threads/repair-log-sega-naomi.456/

- Confirm trace continuity of the super-cap at C29 - make sure the circuit isn't broken on either side.
- Try dumping the BIOS chip and make sure it isn't corrupt.
- Reflow and or replace IC106 and IC107 (main RAM chips)

 

[doccaz]

A few ideas based on the Naomi troubleshooting thread here:
https://www.arcade-projects.com/threads/repair-log-sega-naomi.456/

Thanks!

- Confirm trace continuity of the super-cap at C29 - make sure the circuit isn't broken on either side.

Checked it and it appears to be fine (no broken traces, continuity measured on some nearby vias appear to be okay)

- Try dumping the BIOS chip and make sure it isn't corrupt.

I'm waiting for an adapter for my programmer to read the 27c160, will do!

- Reflow and or replace IC106 and IC107 (main RAM chips)

The traces appear to be perfect on these, but will try as well. I'll look up where I can source these, though...

 

[doccaz]

Update: I got my programmer adapter to read the 27C160. I pulled out the original EPROM, dumped it, and looked up the checksum. It's matches with the version on the label (EPR 23605A).
I burned a new Multi-BIOS on another EPROM, verified, dumped, checked the checksum. It's burned correctly. Still, the Naomi 2 won't boot.

I also finally got ahold of the Hynix TC-10 chips for IC 106 and IC 107. I just replaced them, but it still won't boot. No video signal, no sound. Just the fans running and the two LEDs lit up. Took my time to re-check every pin on those RAM chips under the microscope, and make sure they're all connected, no shorts that I could find.

I'm all out of ideas. Any suggestions?

 

[doccaz]

Oh and these are the replacement chips installed. No ripped traces, all pins are solid. Sorry for the messy flux.

 

[Heinz]

I wouldn't be surprised if the CPU or GPU's are cooked, I had a Naomi 2 shipped over from Japan once and one of the dies literally separated from it's substrate. Try measuring between pins 1 and 6 on the VGA out and it should read 0.7v to see if it's even outputting a signal.

Have you measured the 5,3.3 and 12v lines to make sure they're reading good when the unit is powered on? N2 is a thirsty boy.

 

[nem]

Have you connected anything to the audio output? To make sure it's completely dead and not just playing blind. It should play a jingle on boot up (unless sound is set to off...).

Also, the caps used in these won't bulge or leak. They will just dry out. As a last ditch effort you could throw new caps in it.

 

[doccaz]

I wouldn't be surprised if the CPU or GPU's are cooked, I had a Naomi 2 shipped over from Japan once and one of the dies literally separated from it's substrate. Try measuring between

pins 1 and 6 on the VGA out and it should read 0.7v to see if it's even outputting a signal.

It measure 0.025v.

Have you measured the 5,3.3 and 12v lines to make sure they're reading good when the unit is powered on? N2 is a thirsty boy.

On the ATX connector (under load):
5v = 5.01v
12v = 12.02v
3.3v = 3.34v

On the motherboard:
CN12 (5V) = 4.98v
3.5v test point = 3.44v
3.3v test point = 3.31v
SH4-V test point = 1.93v
2.5v test point = 2.50v

 

[Heinz]

You could try as Nem suggested to replace the caps, honestly I think that's a last resort right next to hunting for broken traces.

 

[MickyMac]

Black screen is a tricky one.

Well done on the ram swap. Triple check your soldering on the ram replacement and use multimeter to check continuity at every pin and test pins to the left/right for bridging.

Check you didn't blow away any smd caps or resistors when replacing the ram with your hot air gun.

The new ram you got could also be bad or the wrong ram type.

Also check continuity of the centre pin on the fans to the mobo. Had a nonbooter that was just the sense pin on the fan had no contact.

Can you send to Ken irepairsega in usa? I would guess it's one of the ram pairs but no public info on diagnosing that. Ken knows how to diagnose the ram chips quickly. (Perhaps he just uses a fast oscilloscope).


Good luck!!

 

[doccaz]

Have you connected anything to the audio output? To make sure it's completely dead and not just playing blind. It should play a jingle on boot up (unless sound is set to off...).

Just hooked up a speaker (had done that when I first got it), still no sound on boot up. I can hear a "pop" when it's turned on, and that's all.

I saw in the Service Manual that there is a configuration to turn off the sound, but wouldn't that be lost without a CR2032 battery? Is there a factory reset jumper or something like that?

Also, the caps used in these won't bulge or leak. They will just dry out. As a last ditch effort you could throw new caps in it.

 

[nem]

I saw in the Service Manual that there is a configuration to turn off the sound, but wouldn't that be lost without a CR2032 battery?

Yes, if you have removed the supercap as well. However, I'm not sure what it defaults to. Default settings could even change between bioses. I like to keep demo sound off and I've noticed sometimes I have to turn it off and sometimes I don't.

 

[doccaz]

Well done on the ram swap. Triple check your soldering on the ram replacement and use multimeter to check continuity at every pin and test pins to the left/right for bridging.

Sorry for the delay. I noticed that my multimeter probes weren't thin enough, so I ordered some needle ones while I decided what to do next. Turns out after testing with the needle probes, there was only one almost imperceptible short on one pin under the microscope. Still, it didn't boot.

Check you didn't blow away any smd caps or resistors when replacing the ram with your hot air gun.

Checked. Before applying hot air on the RAM chips I shielded them with kapton tape.

The new ram you got could also be bad or the wrong ram type.

Even though the seller I found said TC-6 ones would work in place of the TC-10 chips, I was still considering that. But it turns out the Naomi 2 accepted the TC-6 (see below).

Also check continuity of the centre pin on the fans to the mobo. Had a nonbooter that was just the sense pin on the fan had no contact.

Checked that with an oscilloscope, the center pin is pulsing as expected on both fans.

Can you send to Ken irepairsega in usa? I would guess it's one of the ram pairs but no public info on diagnosing that. Ken knows how to diagnose the ram chips quickly. (Perhaps he just uses a fast oscilloscope).

I wish I could, but the costs would be prohibitive for me (I'm in Brazil). I do have a an oscilloscope though (not a high-end one), still learning how to properly use it in these cases.

Now for the good news: I got it to boot, play the jingle, show the logo and enter the test menu:

The RAM chips I swapped are okay . Now I gotta check what IC35 is.

Now for the comical part: I got it booting by chance, as I started poking around and pressing chips while turning it on and off (old habits from repairing Nintendo Switches I guess). . It turns out if I press somewhat hard on IC105 (which is covered with a glued-on heatsink) it WILL BOOT. So, it appears that this is a BGA chip that needs reflow?

As my knucles were getting pretty painful pressing this heatsink, I got some objects to do it for me while I ran the tests you see above... just have to be careful not to get everything crashing down

The problem now is, how to reflow a BGA chip with a glued heatsink and not make half the components fall off the board with the heat...

 

[doccaz]

Weird. Was messing with the Netdimm I got here (had wrong jumpers set!), ran the tests again and IC35 now shows up as good.

The Net-dimm appears to be working fine:

So, the BIOS and PIC I burned for it appear okay. Still have to get some images and the PiDimBoot set up... and some way to reflow that BGA!

Boy these last few months sure have been a learning experience. I have dealt with a few retro consoles before, but the Naomi is something completely new to me.

 

[doccaz]

Got the 32GB WiPiBooter image running on the Raspberry Pi. Played a few Virtua Fighter 4 and Dead or Alive 2 matches without a hitch over the Netdimm. Fans ramped up, no lockups. Neat!
Now to address the grape juice bottle problem... any suggestions?

 

[ShootTheCore]

Performing BGA reflowing properly and professionally isn't straightforward - it requires specialized equipment and templates for each chip die pinout. Ken at iRepairSega was the only guy I knew who was doing it for arcade boards, but I think he stopped due to the effort & expense involved and the low success rate. @Mitsurugi-w was gearing up with the necessary equipment as well a few years ago. I'm not sure if there's anyone else in the scene doing it.

You can roll the dice and try it yourself with a pre-heater, tons of flux and either hot air or an IR rework station. Google around and you'll see plenty of things that people have tried.

Personally, I think it would be cheaper and easier to just buy another Naomi.

 

[doccaz]

well a few years ago. I'm not sure if there's anyone else in the scene doing it.

You can roll the dice and try it yourself with a pre-heater, tons of flux and either hot air or an IR rework station. Google around and you'll see plenty of things that people have tried.

Personally, I think it would be cheaper and easier to just buy another Naomi.

I *was* going to try it, but I noticed yesterday that the heatsink is a bit too "wiggly". Inspecting closer, I see that it's slowly delaminating from the the board itself. It's a matter of time before it disintegrates, especially with the pressure needed to make it work getting larger and larger, unfortunately. It was a fun ride though.

I'll be on the lookout for another Naomi 2.

Thanks for all the tips, guys. I certainly learned a lot (and now have a spares motherboard).