Sega Model 3 video issues

PCB problems and fixes
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Hydreigon
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Sega Model 3 video issues

Post by Hydreigon » May 21st, 2019, 3:32 pm

Game: Lost World Jurassic Park

After a few hours, ~6-8 hours, of uptime, one of these 3d issues would happen:
  • The female T-Rex would load wrong textures on some parts of the jaw and inside the mouth.
  • The 3d graphics would flicker.
  • No 3d graphics would show at all.
My initial thought was the boards weren't receiving the proper airflow due to some caked dust so I cleaned out the cage and boards; didn't fix the issue. Memory test shows rom and ram all good but displays a vertical dashed line of white pixels (disappears upon exiting the test mode however). I have not checked the voltages from the power supply yet. Could this be a video board issue?

If anyone else knows about Model 3, I noticed there is no mention of a step 1.5 on both the cpu and video boards of this Lost World boardset. I heard the only difference is the gpu overclocked on the video board. I'll save this discussion for a different thread.

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LEGENOARYNINLIA
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Re: Sega Model 3 video issues

Post by LEGENOARYNINLIA » May 21st, 2019, 5:14 pm

VF3tb which is also a Model 3 title is known to load wrong textures from time to time, and I think it's an awesome feature. :awe:



This happened just this Saturday. 8-)

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outrun2
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Re: Sega Model 3 video issues

Post by outrun2 » May 21st, 2019, 5:18 pm

Difficult to say, most likely a video board issue but step 1.5 video boards are more reliable than step 2 boards in my experience.

Could also be the ROM board so worth trying a different game on the stack if you can.

Always worth checking voltages particularly if you have an original Model 3 PSU which are known to be unreliable when they get old. A known 100% worker or better still a Sun PSU out of a Naomi is a better option.

For info step 1.5 boards just have 'Model 3 etc.' marked on them while step 2.0 and step 2.1 boards have 'Model 3 Step 2 etc.' marked on them. The .x isn't mentioned.
Found:
Sega Model 3 Dirt Devils ROM board or complete boardset ;)

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Re: Sega Model 3 video issues

Post by Hydreigon » May 21st, 2019, 6:06 pm

My most likely guess is a certain component eventually shutting down from improper voltage and/or overheating. My next steps are to reseat/clean all the roms on the rom board, check/adjust power supply voltages and replace both fans. I'd appreciate any good suggestions for Sega Model 3 fan replacements, two of them.

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grantspain
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Re: Sega Model 3 video issues

Post by grantspain » May 22nd, 2019, 2:20 am

more likely the smt components on the video board are failing due to bad solder contact or even video ram breaking down

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Re: Sega Model 3 video issues

Post by Hydreigon » June 14th, 2019, 3:51 am

Lowered the +5v and +3.3v down to near normal values. The issue got worse a few days after with the game freezing ~20 minutes after startup. My next step is now to check all boards and replace the fans.

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Re: Sega Model 3 video issues

Post by Hydreigon » June 15th, 2019, 5:41 pm

Nobody has any suggestions for replacing the case fans on a Sega Model 3? C'mon guys. I'm certain one of you has replaced them before and the factory fans can't last forever.

EDIT: May take a look at the whole pcb set one day so I can find out what fans are used.
Last edited by Hydreigon on June 15th, 2019, 6:37 pm, edited 1 time in total.

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nem
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Re: Sega Model 3 video issues

Post by nem » June 15th, 2019, 6:05 pm

The case is pretty snug, so I put some standard 20mm deep fans on the outside.

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