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Sega Naomi universal monitor issue

Printed From: ukVac.com
Category: Technical
Forum Name: Tech, Maintenance & Repairs
Forum Description: Need Help? Ask Here
URL: http://www.ukvac.com/forum/forum_posts.asp?TID=385614
Printed Date: 21 Sep 2021 at 2:39am


Topic: Sega Naomi universal monitor issue
Posted By: Rob_bob_2k6
Subject: Sega Naomi universal monitor issue
Date Posted: 09 Sep 2021 at 2:23pm
I had a Naomi universal delivered today, which was working before being shipped.

Now when I turn it on I get horizontal lines which then fade and the screen stays blank.

Is anyone able to offer an troubleshooting help please?

I’ve tried a Dreamcast into the vga port in case it was the Naomi motherboard and that does the same thing.

Thanks a lot for any help



Replies:
Posted By: gunblade
Date Posted: 09 Sep 2021 at 2:27pm
reseat the neck card and all connectors to the chassis- you will need to take the plastic cover off the back of the cab
locate screen volts adjustment pot on flyback and turn anti clockwise a small amount


Posted By: devtty0
Date Posted: 09 Sep 2021 at 2:30pm
On my naomi, it gets a blank screen when I first turn it on, if I leave it on for a short while and then power cycle it, I see a screen which quickly fades to black.

If I then leave it on a bit longer, if I power cycle again, the picture comes up and stays on.

Dont know whats happening, but it at least works. Caps maybe? 

There is also a fizzing sound from the annode, which sounds like its fizzing out when it fades to back, and stays when the picture stays. 


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wanted :
sega model 3 racing games
namco system 22 racing games
model 3 to naomi psu adapter


Posted By: Fantazia2
Date Posted: 09 Sep 2021 at 2:45pm
I would say check the seating of all the cables related to the monitor, including the remote board that is in the control panel area, but you will need to remove the screen surround to access that I think from memory.

Something could have rattled loose during transport.

Also with the rear plastic surround off when the screen goes blank have a look to see if its losing neck glow.


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 2:45pm
I’ve done than and now get the horizontal white lines on a grey screen but it doesn’t fade it stays on the screen.


Posted By: Fantazia2
Date Posted: 09 Sep 2021 at 2:49pm
As mentioned by DevTTY the Naomi MB's sometimes take a while to boot, if you leave it for a while do you hear anything coming our of the speakers, pretty sure they have a boot up sound.

If you could stick a picture up of what your seeing that might help.


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 2:55pm
The game is playing out of the speakers, so is def in game.

Neck doesn't ever seem to glow all that bright.

Im taking the surround off now to check connections there.

I had already reseated the cables on the chassis.

Thanks


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 3:04pm
Taken the control panel off, nothing seemed lose. Seated a few bits and no difference.


Posted By: jinq-sea
Date Posted: 09 Sep 2021 at 3:05pm
Is the ground wire connected on the neck card?


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 3:20pm
I can’t see anything lose that looks like it


Posted By: jinq-sea
Date Posted: 09 Sep 2021 at 3:29pm
Upload some pics with the back off - might be sensible.


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 3:31pm
Heres on of the neck card whilst running:


Posted By: jinq-sea
Date Posted: 09 Sep 2021 at 3:37pm
Chassis too would help if you can Smile


Posted By: Sbdesign
Date Posted: 09 Sep 2021 at 3:41pm
did you turn the gain up or down?
it looks like you turned it up


-------------
-Selling soon:
-RECENT SOLD- DAYTONA 2 TWIN // NNC / KOR66 / SEGA RALLY 3 DX / VC2 / HOTD / ASTEROIDS


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 3:43pm


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 3:44pm


Posted By: Velyks
Date Posted: 09 Sep 2021 at 3:49pm
You can see the retrace lines, I think your screen volts are up way too high. To lower them it should be the knob/dial labeled "SCREEN" on the back of the flyback.


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:04pm
Would that be anti clockwise?


Posted By: jinq-sea
Date Posted: 09 Sep 2021 at 4:08pm
It really does look like the screen volts are turned right up yes! Screen pot on the flyback - turn it a little anticlockwise. Gunblade (who knows a sh*tload about monitors) suggested this above. Try it :thumb:


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:09pm
It’s already as far as it will go anti clockwise


Posted By: gunblade
Date Posted: 09 Sep 2021 at 4:13pm
if screen volts has no affect then its possible for some strange reason you have lost video b+ 200v which is normally an open circuit resistor- there is usually a reason for this, its not something that would just happen


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:15pm
It does have an effect, since turning it anti clockwise the screen maintains those lines rather than fading.

When first turning it on it would keep the lines on screen for a few seconds then fade.

Was shown a video of it working through what’s app, then Martin has had it for 2 weeks now delivered with no picture, so not sure what could have happened to it.


Posted By: Fantazia2
Date Posted: 09 Sep 2021 at 4:19pm
The ribbon cable with the grey cables and a couple of green and a red one, that is the cable for the renote adjustment board that is inside the control panel, I would check that is all plugged in and secure at both ends, you could also try adjusting the pots on the remote board and see if that causes any changes on the screen.

You will need to remote the front monitor surround to access the cable plugged into the remote adjustment board from memory.


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:23pm
The controls on the front panel do adjust picture size etc, but none of them make the game show.

Cheers


Posted By: gunblade
Date Posted: 09 Sep 2021 at 4:30pm
if your flyback line remain then most likely you have lost the video b+


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:31pm
Is that fixable?


Posted By: jinq-sea
Date Posted: 09 Sep 2021 at 4:33pm
Just curious @Rob_bob_2k6 - did you leave the cab to acclimatise a bit before you turned it on?


Posted By: gunblade
Date Posted: 09 Sep 2021 at 4:35pm
Originally posted by Rob_bob_2k6 Rob_bob_2k6 wrote:

Is that fixable?

yes you just check the resistor with a meter and if open you replace it


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 4:55pm
Jinq-only maybe 20-30mins after bringing it in.

Gunblade- I do have a multimeter here but wouldn’t really know what to do to be honest.


Posted By: gunblade
Date Posted: 09 Sep 2021 at 6:00pm
just looked at the schems and the issue is more likely to be r517 3r3 ohm 1w metal oxide, it's actually on the heater circuit rather than video b+

if you feel the need to check that resistor with your meter then DO NOT have the chassis powered


Posted By: Rob_bob_2k6
Date Posted: 09 Sep 2021 at 6:05pm


Posted By: Rob_bob_2k6
Date Posted: 14 Sep 2021 at 9:52pm
Update:


Posted By: thegreathopper
Date Posted: 15 Sep 2021 at 7:38am
Well done on the repair, what was the fault?


Posted By: Rob_bob_2k6
Date Posted: 15 Sep 2021 at 9:13am
Had to send the chassis off for repair. Was the victim of a bodged repair so didn’t survive transit. A bad job had been made of replacing a capacitor on the Board and caused damage. Also had a snapped neck card which had been bodged. New neck card and new capacitor and now up and running.


Posted By: mozie
Date Posted: 15 Sep 2021 at 9:38am
Par for the course in this game, ops done anything they could to keep the games running, can't count the amount of ms8/9 chassis I've seen with jumper wires and bodge jobs on them, least you have it sorted should last a long time (or maybe not as is the nature of these thing unfortunately)


Posted By: Fantazia2
Date Posted: 15 Sep 2021 at 10:23am
Have you got some pictures of the snapped neck card, looks ok if the previous pictures you had posted?

Would be interested to see as heard of some dodgy repairs before on neckcards on the Broken Token Podcast.


Posted By: Rob_bob_2k6
Date Posted: 15 Sep 2021 at 10:25am
Nope, it was replaced and I haven’t seen a photo of the old one. I do trust what I was told though.


Posted By: tin
Date Posted: 15 Sep 2021 at 11:13am
Ahh yeah I can see at least a crack in the neckboard in the previous pictures now you mention it. I guess this is the way with these things, they all will have many repairs and hoiking them about means any of then could give at any moment. Hell I've got two cabs that were working, I haven't moved them an inch and now they aren't.



Posted By: Fantazia2
Date Posted: 15 Sep 2021 at 11:35am
Originally posted by tin tin wrote:

Ahh yeah I can see at least a crack in the neckboard in the previous pictures now you mention it. I guess this is the way with these things, they all will have many repairs and hoiking them about means any of then could give at any moment. Hell I've got two cabs that were working, I haven't moved them an inch and now they aren't.


Now you say that I can see it, missed there was another photo earlier in the thread of the neckboard from the side and can see the damage on that, and using that can see a bit on the other photo by a matching up where the damage is.


Posted By: Amb47uk
Date Posted: 15 Sep 2021 at 11:40am
Shame that wasn't pointed out to you when you bought it, but it's plausible it wasn't noticed by them either.

It can't have been cheap to replace. Hope the seller helped you out somewhat.


Posted By: Rob_bob_2k6
Date Posted: 15 Sep 2021 at 11:41am
Nope


Posted By: gunblade
Date Posted: 15 Sep 2021 at 12:41pm
repairable but best to replace as i had a spare, and the breaks were over delicate points



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