Sega naomi installed with netboot raspberry pi but no visuals

k1702

Timid Neo Newbie
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May 12, 2021
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Hello everyone, l just installed a sega naomi 1 with netboot raspberry pi mod.The board appears to be functional,voltage is within norms,the raspberry pi is functional ,l am seeing the lcd screen on the pi fired up with the options to scroll and select game to flash to the netboot dimm.There is no visual, the lcd screen connected to the vga out installed boots up with the acer monitor logo then goes to blank with a no signal error.
I researched online, and came to some conclusions, nothing is wrong with the board physically, but the board doesnt like the lcd monitor or vice versa.Given the age of the naomi itself , it doesn't display on modern monitors, but older lcd screens or CRT monitors.
From what l gathered ,
1.l can find a older lcd monitor from the early 00s or
2.Use a RGB to VGA adapter to convert the RGB signals from the jamma harness to a signal the lcd monitor will possibly accept(l have used the same adapter for my neogeo MVS 1 slot and my CPS2 board with no issues)

What do you guys think?Are there other workarounds? Would using the RGB to VGA adapter resolve the issue?
Thanks in advance for any insights!
 

skate323k137

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Jan 7, 2013
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3,407
Starting simple, are all the DIP switches on the NAOMI itself OFF? If DIP1 is on you'll have 15k video which is JAMMA compatible not VGA. DIP1 off should be 31k standard 640x480 that most displays will accept. The issue with Naomi is there is some non standard use of one of the VGA pins, but I honestly don't recall the specifics other than to use a cable that's missing that pin on newer monitors.
 

k1702

Timid Neo Newbie
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May 12, 2021
Posts
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Starting simple, are all the DIP switches on the NAOMI itself OFF? If DIP1 is on you'll have 15k video which is JAMMA compatible not VGA. DIP1 off should be 31k standard 640x480 that most displays will accept. The issue with Naomi is there is some non standard use of one of the VGA pins, but I honestly don't recall the specifics other than to use a cable that's missing that pin on newer monitors.
Hey,thanks for the response, l confirm all 4 dip switches on the naomi board are on the off position (on the down position ).The vga cables with the missing pin you mentioned , do you know where l can find them online?
The rgb to vga adapter l have, do you think it would resolve this issue?
 

skate323k137

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Jan 7, 2013
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So not to confuse you further, but VGA is RGB, just at a higher refresh rate. You might have to flip DIP1 on the NAOMI to get 15k RGB in order for your adapter to upscale it back to 480p VGA which is not ideal at all. We just want to pull 480P VGA right from the NAOMI :)

pin 9 is the one in question, but if it caused an issue with your display and cable, something would probably be quite obviously wrong https://www.arcade-projects.com/threads/repair-log-sega-naomi.456/page-3#post-118230

To be completely safe moving forward you need a cable missing pin 9 especially if you're going to try any different displays:

Failing that my next personal step would be a sync stabilizer like the extron SS-200, but it's BNC so you would need VGA->BNC adapters/cables for this particular device

 

k1702

Timid Neo Newbie
Joined
May 12, 2021
Posts
9
So not to confuse you further, but VGA is RGB, just at a higher refresh rate. You might have to flip DIP1 on the NAOMI to get 15k RGB in order for your adapter to upscale it back to 480p VGA which is not ideal at all. We just want to pull 480P VGA right from the NAOMI :)

pin 9 is the one in question, but if it caused an issue with your display and cable, something would probably be quite obviously wrong https://www.arcade-projects.com/threads/repair-log-sega-naomi.456/page-3#post-118230

To be completely safe moving forward you need a cable missing pin 9 especially if you're going to try any different displays:

Failing that my next personal step would be a sync stabilizer like the extron SS-200, but it's BNC so you would need VGA->BNC adapters/cables for this particular device

Hey man, thanks again for the response and the links,l didn't know rgb was vga at a higher refresh rate ! Lol.
I was trying to aim for 480p with a direct connection as you said,but given the issue with recent gen lcd monitors and near impossible task of finding and repairing CRT monitors where l am from, l am settling to install the vga adapter.Not the best solution, but it is serviceable, l used the same adapter for my MV1F and CPS 2.

Thanks for the help,it's appreciated!
 

skate323k137

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No problem, best of luck :)

And just to clarify, it is VGA with the higher refresh rate (31k); most people when they say RGB in gaming mean SCART and/or JAMMA both of which are 15k signals (albeit at different voltages). At the end of the day though, both consist of R G B and Sync signals, and VGA can also split the sync from composite to H/V. Most VGA monitors accept composite sync on the H sync pin.
 

k1702

Timid Neo Newbie
Joined
May 12, 2021
Posts
9
No problem, best of luck :)

And just to clarify, it is VGA with the higher refresh rate (31k); most people when they say RGB in gaming mean SCART and/or JAMMA both of which are 15k signals (albeit at different voltages). At the end of the day though, both consist of R G B and Sync signals, and VGA can also split the sync from composite to H/V. Most VGA monitors accept composite sync on the H sync pin.
Thanks for setting me straight!

Just one final question,noob question, from what l described in my first post, did l short out the board by using the normal vga cables instead of the sega OEM vga cable or the vga without pin 9?

Thanks for indulging me
 

skate323k137

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No problem. The answer to that question lies in the design of the target display you tried. If you don't want to go down the multi meter route, try to borrow a normal old PC CRT monitor and try that on 31k (all dips off)
 

k1702

Timid Neo Newbie
Joined
May 12, 2021
Posts
9
No problem. The answer to that question lies in the design of the target display you tried. If you don't want to go down the multi meter route, try to borrow a normal old PC CRT monitor and try that on 31k (all dips off)
Ok, will do that, once again, your help has been invaluable, thanks so much and all the best!
 
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