Sega Naomi 2 Ramdac issue

PCB problems and fixes
Post Reply
User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Sega Naomi 2 Ramdac issue

Post by Hydreigon » April 30th, 2019, 3:38 am

Ouch, how the heck am I going to replace this?

This is from the slave pcb from that same ID3 twin I mentioned in an earlier thread. I narrowed the issue down to the motherboard all right as that board won't boot at all.
The master pcb has these Ramdac chips:

I am guessing either this is a different rev or the previous owner replaced those chips at some point.

Thanks

User avatar
nem
Posts: 1524
Joined: August 17th, 2008, 6:59 pm
Location: Finland

Re: Sega Naomi 2 Ramdac issue

Post by nem » April 30th, 2019, 11:26 am

IMO the soldering looks too clean for the chips to have been replaced.

That's a good find though. Not only did you find the likely culprit, you also found a replacement part for it. Not sure if it's common knowledge or not, but I didn't know the 315-6258 could be replaced with an off the shelf part.

As for replacing, I suggest contacting someone who does SMD work and shipping it to them. Neither removing the original IC (legs on all four sides) nor soldering the new IC in (fine pitch) is very beginner friendly.

User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Re: Sega Naomi 2 Ramdac issue

Post by Hydreigon » April 30th, 2019, 2:21 pm

nem wrote:
April 30th, 2019, 11:26 am
IMO the soldering looks too clean for the chips to have been replaced.

That's a good find though. Not only did you find the likely culprit, you also found a replacement part for it. Not sure if it's common knowledge or not, but I didn't know the 315-6258 could be replaced with an off the shelf part.

As for replacing, I suggest contacting someone who does SMD work and shipping it to them. Neither removing the original IC (legs on all four sides) nor soldering the new IC in (fine pitch) is very beginner friendly.
Finding a chip like that is my first priority. I wonder if Hrvat9 had that same issue with a broken Naomi 2 he has worked with. I didn't know an issue with a Ramdac or NTSC/PAL digital video encoder could happen on a Naomi 2 until now. To be honest, I found out by accident from touching some important chips only to find out a certain one "stung" my finger and that's when I found out that chip was cracked.

This component isn't an easy find either. It's a 14x4 pin digital video encoder. I couldn't find much results from searching the two chips the working pcb uses, BU1428KS.

EDIT: Both sets of encoders are identical and are the same DAC/encoder used in a Dreamcast. Reverse engineering that chip for reproduction would be crucial at this point.

User avatar
leonardoliveira
Posts: 689
Joined: August 30th, 2012, 5:53 am
Location: Brazil
Initials: leo

Re: Sega Naomi 2 Ramdac issue

Post by leonardoliveira » May 4th, 2019, 5:21 pm

Buy a Dreamcast with broken drive and salvage it from there.

Image
Image

User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Re: Sega Naomi 2 Ramdac issue

Post by Hydreigon » May 6th, 2019, 2:31 am

leonardoliveira wrote:
May 4th, 2019, 5:21 MP
Buy a Dreamcast with broken drive and salvage it from there.
Someone clearly didn't see a small part in my last post.
Hydreigon wrote:
April 30th, 2019, 2:21 MP
Reverse engineering that chip for reproduction would be crucial at this point.
This is especially the case for arcade hardware that wasn't common to begin with like Namco System 22.

User avatar
leonardoliveira
Posts: 689
Joined: August 30th, 2012, 5:53 am
Location: Brazil
Initials: leo

Re: Sega Naomi 2 Ramdac issue

Post by leonardoliveira » May 8th, 2019, 6:54 am

Reverse engineering has been done already. I thought you just wanted to fix your board.

Look for the DC HDMI thing.
Image

User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Re: Sega Naomi 2 Ramdac issue

Post by Hydreigon » May 10th, 2019, 3:15 pm

leonardoliveira wrote:
May 8th, 2019, 6:54 am
Reverse engineering has been done already. I thought you just wanted to fix your board.

Look for the DC HDMI thing.
I was under the impression that if reverse engineering had been done, then I would have started repairs on my N2 weeks ago and this thread wouldn't exist. That for some reason isn't the case. The DC HDMI thing you speak of is most likely useless on a N2 because of the different schematics. I am pretty much stuck as a result.

Hrvat9
Posts: 171
Joined: April 26th, 2017, 3:47 pm
Location: Canada
eBay: hrvaat

Re: Sega Naomi 2 Ramdac issue

Post by Hrvat9 » May 24th, 2019, 1:13 pm

I still have my n2 mobo that boots to a black screen , assuming it’s the two rams , I think ic107 and 108 (under one of the gpus). I got a spare n2 mobo for 5 bucks locally, but had a cap broken off, it would boot to some fuzzy stuff but did show life. Found a spot to connect the cap to since one off the solder pads were ripped off and I got a working Naomi 2 for 5 bucks :D (a friend found the solder spot to attach the cap to)

So I have both Id3 gams working !!! Finally. I’m just waiting for the slave side monitor to be fixed

Hydreigon wrote:
April 30th, 2019, 2:21 MP
nem wrote:
April 30th, 2019, 11:26 am
IMO the soldering looks too clean for the chips to have been replaced.

That's a good find though. Not only did you find the likely culprit, you also found a replacement part for it. Not sure if it's common knowledge or not, but I didn't know the 315-6258 could be replaced with an off the shelf part.

As for replacing, I suggest contacting someone who does SMD work and shipping it to them. Neither removing the original IC (legs on all four sides) nor soldering the new IC in (fine pitch) is very beginner friendly.
Finding a chip like that is my first priority. I wonder if Hrvat9 had that same issue with a broken Naomi 2 he has worked with. I didn't know an issue with a Ramdac or NTSC/PAL digital video encoder could happen on a Naomi 2 until now. To be honest, I found out by accident from touching some important chips only to find out a certain one "stung" my finger and that's when I found out that chip was cracked.

This component isn't an easy find either. It's a 14x4 pin digital video encoder. I couldn't find much results from searching the two chips the working pcb uses, BU1428KS.

EDIT: Both sets of encoders are identical and are the same DAC/encoder used in a Dreamcast. Reverse engineering that chip for reproduction would be crucial at this point.
candy: Sega New Astro City , Sega Versus City
Seeeegggggaaaaaa

User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Re: Sega Naomi 2 Ramdac issue

Post by Hydreigon » May 24th, 2019, 2:26 pm

Hrvat9 wrote:
May 24th, 2019, 1:13 MP
I still have my n2 mobo that boots to a black screen , assuming it’s the two rams , I think ic107 and 108 (under one of the gpus). I got a spare n2 mobo for 5 bucks locally, but had a cap broken off, it would boot to some fuzzy stuff but did show life. Found a spot to connect the cap to since one off the solder pads were ripped off and I got a working Naomi 2 for 5 bucks :D (a friend found the solder spot to attach the cap to)

So I have both Id3 gams working !!! Finally. I’m just waiting for the slave side monitor to be fixed
I unfortunately didn't get both sides running yet. Got another Naomi 2 which I thought wouldn't boot due to bad fans but not only that but the other Naomi 2 doesn't power on at all. I wish I had that same luck as you did. Did you actually check those DAC/RAMDAC chips on your bad Naomi 2 motherboard to see if one of them was cracked?

User avatar
leonardoliveira
Posts: 689
Joined: August 30th, 2012, 5:53 am
Location: Brazil
Initials: leo

Re: Sega Naomi 2 Ramdac issue

Post by leonardoliveira » May 24th, 2019, 7:41 pm

Hydreigon wrote:
May 10th, 2019, 3:15 MP
leonardoliveira wrote:
May 8th, 2019, 6:54 am
Reverse engineering has been done already. I thought you just wanted to fix your board.

Look for the DC HDMI thing.
I was under the impression that if reverse engineering had been done, then I would have started repairs on my N2 weeks ago and this thread wouldn't exist. That for some reason isn't the case. The DC HDMI thing you speak of is most likely useless on a N2 because of the different schematics. I am pretty much stuck as a result.
I was talking about how the research has been done already. If you want something out of that, go ask them. Now, about the original part I just said you can just take the parts you need from a dead dreamcast and let it rest. These chips are bespoke parts and aren't used on anything but NAOMI, Dreamcast and Atomswave.
Image

User avatar
nem
Posts: 1524
Joined: August 17th, 2008, 6:59 pm
Location: Finland

Re: Sega Naomi 2 Ramdac issue

Post by nem » May 25th, 2019, 9:31 am

leonardoliveira wrote:
May 24th, 2019, 7:41 MP
These chips are bespoke parts and aren't used on anything but NAOMI, Dreamcast and Atomswave.
I couldn't find BU1428, but I did find quite a few BU142* datasheets. Has anyone actually contacted ROHM to ask for a replacement part for BU1428KS?

User avatar
Hydreigon
Posts: 42
Joined: December 9th, 2018, 5:48 pm
Location: Milwaukee, WI
eBay: hydreigon223
Initials: HYD

Re: Sega Naomi 2 Ramdac issue

Post by Hydreigon » May 25th, 2019, 4:18 pm

nem wrote:
May 25th, 2019, 9:31 am
leonardoliveira wrote:
May 24th, 2019, 7:41 MP
These chips are bespoke parts and aren't used on anything but NAOMI, Dreamcast and Atomswave.
I couldn't find BU1428, but I did find quite a few BU142* datasheets. Has anyone actually contacted ROHM to ask for a replacement part for BU1428KS?
I should have mentioned "BU1426KS" as well.

Post Reply