[Repair Log] Sega NetDIMM

[doccaz]

Got me another NetDIMM with the latest Naomi 1 I bought (see the other thread).

Appears to be in good condition, no blown caps, no corrosion. Screws are "factory-tight", no fingerprints inside the metal plate. No missing/bent pins on the Omron connectors. Battery inside is completely discharged and dirty.
256MB Samsung RAM stick, also dirty. Doesn't appear to have been messed with before.

The jumpers on the NIC were set to GDROM. Set them to network boot, and I can see that the NIC LEDs just flash briefly with red, then turn off.

Replaced the buffer chip (original was a Fairchild):

Replaced the RAM stick. Same problem.

Removed IC36 (TSOP-4, it reads fine. It's a Fairchild(?) 29LV160TE.
XgPro was able to read it as SPANSION MBM29LV160TE@TSOP48 (id matched).

Saved image has a SHA-1 of b7b5a55a6a4cf0aa2df1b3dff62ff67f864c55e8, and the chip was marked FPR23718, which appears to be firmware version 2.03 according to MAME source code...

Flashed the 3.17 firmware to it (chip was reading/writing fine, so... let's reuse it).
Soldered it back, checked all pins:

When I power it up, I can see the LEDs on the DIMM board light up (including the charging circuit for the battery if I plug it), and the LEDs on the NIC are behaving more normally, and flash with traffic I confirmed it negotiated 100mbit. But still doesn´t boot. One difference I noticed is that it tries to init the video first before giving up.

I can plug in my other Netdimm (3.17 upgraded to 4.01) and it'll work fine, so the Naomi itself is okay.

Any ideas?

 

[doccaz]

Re-checked the pins on the BIOS... found two "floating" pins, resoldered... but still no go.

 

[doccaz]

Interesting: the multi-bios was set to Export (dipsw 4 up) as I was testing with my other Netdimm. Set it back do Japan, and it boots... but I get an error 22 (and firmware 0.00 in test mode).

Maybe I should try using a new chip for the BIOS instead of using the old one?

 

[doccaz]

Ok, I noticed that the ninth pad from right to left was missing the "tip", as in, it appears to have cracked and lost connection. Here's my repair with enameled wire:

And here's the final result with the new chip:

But... it still won't boot. It's back to just flashing the display once, which tells me that it probably did *not* have contact on that pin last time (when it showed me an error 22/dimm timeout).

There's something else failing down the line... but what?

 

[doccaz]

Interesting: if I take out just the NIC, it boots, but fails with error 22.

 

[Elfito69]

i was battling with that dreadfull error 22 but was not able to resolve it, i contacted Ken the sega guru and he told me that the 15-6154 custom burns and causes that error

 

[doccaz]

i was battling with that dreadfull error 22 but was not able to resolve it, i contacted Ken the sega guru and he told me that the 15-6154 custom burns and causes that error

Unfortunately I think you're correct: I exchanged just the NIC on my working NetDIMM, and it works fine. The problem lies in the DIMM board itself.

I guess it's time to look for another cheap DIMM somewhere and use this one for spares.

 

[doccaz]

So, after a few months of looking for a reasonable auction for a new NetDimm to buy, I decided to get a regular GD-ROM one with no network port, as they were going for cheap, and almost no one seems to be bidding hard on them. Since I had a working NIC board (see above), I decided to take a risk and see just swapping it would work with a non-LAN Netdimm. The ones with a LAN port are reaching some astronomic prices lately!
So, here it is, unmodified:

I plugged it in my Naomi 2, and I could see the "GD-ROM system" banner, and it was recognized in test mode. Running BIOS version 1.02. The DIMM tests fail...

Got some very dirty connectors, and the BIOS chip is 56-pin (the one with the FPR-23483C label). Well, time to remove it with hot air:

... and we're done without ripping any pads:

Programmed a new TSOP-48 chip with BIOS v3.17 and soldered it to the alternative pad positions:

.. and it boots with the "Network System" banner, but I cannot save any network settings (gives me a DIMM Timeout error every time). It also failed the DIMM tests under Test mode. After fiddling a few times with contact cleaner on all connectors and re-seating the memory sticks, I finally got it to work, accept the network settings and pass the tests.

I then booted a game with WiPi Netbooter to check if it was indeed functional (that's Azumanga Daioh BTW):

... and hit the Update Firmware button on the Netbooter. Presto, we now have a working LAN-capable with BIOS 4.01:

Later I reassembled it in the case, and we're done!

 

[doccaz]

I got curious whether the "old" board that I serviced months earlier with new chips and was crapping out would work with the "new" GDROM interface... and it does boot with the "GD-ROM system" banner, so it might still be useable somehow

I just don't have a working GD-Rom drive to test it (and no reason to get one), so... maybe I'll sell this one.

 

[mathieulh]

So, after a few months of looking for a reasonable auction for a new NetDimm to buy, I decided to get a regular GD-ROM one with no network port, as they were going for cheap, and almost no one seems to be bidding hard on them. Since I had a working NIC board (see above), I decided to take a risk and see just swapping it would work with a non-LAN Netdimm. The ones with a LAN port are reaching some astronomic prices lately!
So, here it is, unmodified:

I plugged it in my Naomi 2, and I could see the "GD-ROM system" banner, and it was recognized in test mode. Running BIOS version 1.02. The DIMM tests fail...

Got some very dirty connectors, and the BIOS chip is 56-pin (the one with the FPR-23483C label). Well, time to remove it with hot air:

... and we're done without ripping any pads:

Programmed a new TSOP-48 chip with BIOS v3.17 and soldered it to the alternative pad positions:

.. and it boots with the "Network System" banner, but I cannot save any network settings (gives me a DIMM Timeout error every time). It also failed the DIMM tests under Test mode. After fiddling a few times with contact cleaner on all connectors and re-seating the memory sticks, I finally got it to work, accept the network settings and pass the tests.

I then booted a game with WiPi Netbooter to check if it was indeed functional (that's Azumanga Daioh BTW):

... and hit the Update Firmware button on the Netbooter. Presto, we now have a working LAN-capable with BIOS 4.01:

Later I reassembled it in the case, and we're done!

Why would you flash 4.01 when you can flash 4.03 to get (non Hagiwara branded) CF and CD-R capabilities?

 

[doccaz]

Why would you flash 4.01 when you can flash 4.03 to get (non Hagiwara branded) CF and CD-R capabilities?

Because it'll be used solely for network booting (no CF or CD-R). It can be upgraded later via the Netbooter, but only to 4.02.
Where can I find the 4.03 image to download?

 

[Mrhide]

Where can I find the 4.03 image to download?

https://github.com/mathieulh/SEGA_DIMM_CD-R

 

[Hackcell]

Cool! Thanks for sharing!

 

[PlatynumX]

Is that 4.03 update netbootable?