Print Page | Close Window

Model 3 wont boot

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=367197
Printed Date: 11 Dec 2018 at 11:08pm


Topic: Model 3 wont boot
Posted By: Kev A
Subject: Model 3 wont boot
Date Posted: 26 Nov 2018 at 9:55am
Having a bit of a problem with my Daytona 2 stack, (For background it did always have a faulty video ram) but played OK with only minor glitches, and given the cost of video boards I decided to live with it.

For a while now its been having trouble booting requiring a couple of power cycles to start up, I originally thought this was PSU related but have swapped out the PSU with no improvement, checked the chips are getting 5.1v etc.

Anyway most of the time now it just boots to a black screen but sometimes comes up with this error message, and unable to access the test menu....



BACKUP RAM : UNREADABLE .. HALTED.

I'm guessing its terminal, having played around model 2 stuff even a completely borked video board will boot, but I don't have much experience with model 3 stuff so any ideas if its the video or CPU board that's causing it?



Replies:
Posted By: bonehead
Date Posted: 26 Nov 2018 at 10:05am
My guess is it’s the cpu board as I have one that won’t boot properly and I have tested a working cpu and all is ok.
I could be wrong but that’s my thought.

-------------
Always looking for a bargain.
Wanted., bezerk, mad planets.


Posted By: keropi
Date Posted: 26 Nov 2018 at 10:17am
could that backup ram error mean that some sort of sram or rtc clock is dead so settings can't be read and the board stops booting? I could check this first as the cpu seems to pass the tests...


Posted By: Kev A
Date Posted: 26 Nov 2018 at 11:35am
Well glad to hear its probably the CPU board, if the worst come to the worst it will be cheaper to replace.

Any idea where those components are, would they be near the battery?


Posted By: obcd
Date Posted: 27 Nov 2018 at 9:09am
If there is a battery on the board I would measure it's voltage. It's pretty old hardware and if the battery is totally dead it could prevent the cpu from properly reading the nvram resulting in your error. Also check if it hasn't leaked and maybe coorosion damaged a pcb trace.


Posted By: Kev A
Date Posted: 27 Nov 2018 at 10:05am
I replaced the battery as the old one measured 2.8v, It doesn't look like to me like there has been any leakage. I have reflowed the solder on the battery holder pins, and the supercap,(I have read a bad supercap can cause Naomis to black screen so have ordered a replacement)

I have tested continuity on the traces running under the battery and around the supercap on both sides and cant find any broken traces, here's a couple of pics. I have identified a few of parts and labeled them...








Posted By: big10p
Date Posted: 27 Nov 2018 at 10:22am
Have you de-soldered the super cap to check it? Last one I replaced looked fine, but was badly corroded underneath. If this has happened to yours, it may have damaged traces.


Posted By: Kev A
Date Posted: 27 Nov 2018 at 10:31am
Yeah I took it off to check and re do the solder, looked ok, don't suppose I could use a normal cap to test, or is there something special about the super cap?


Posted By: big10p
Date Posted: 27 Nov 2018 at 10:37am
Can't speak for model 3, but on a regular NAOMI 1, I'm pretty sure all the super cap does is allow the coin battery to be changed, without wiping the settings RAM. I believe you can remove the super cap and the board will run fine without it.


Posted By: Kev A
Date Posted: 27 Nov 2018 at 10:56am
Yeah I couldn't find much info on the supercap regarding model 3, but I assume its similar to the Naomi, it doesn't boot either with the supercap removed but I think I will replace it anyway when the new one arrives, its easy enough to get to so may as well. If that doesn't work I'm kind of out of ideas where to look next, I think the chances of me being able to sucessfully replace any of the surface mounted components is pretty slim.


Posted By: Kev A
Date Posted: 29 Nov 2018 at 4:54pm
Supercap replaced and still no change, think I'm going to double check all the continuity in that area, if the battery is installed should I be seeing voltage on the vcc pins of the srams all the time?


Posted By: big10p
Date Posted: 29 Nov 2018 at 5:23pm
Originally posted by Kev A Kev A wrote:

Supercap replaced and still no change, think I'm going to double check all the continuity in that area, if the battery is installed should I be seeing voltage on the vcc pins of the srams all the time?
I imagine so, else the settings would get wiped.


Posted By: Kev A
Date Posted: 29 Nov 2018 at 8:26pm
Ok so I got 3v on the vcc pins of the srams nearest the battery, increasing to 5v when booted ao im sure they are getting power. Also double checked continuity in that area and dint find anything. Short of replacing the srams im not sure there is much else I can try.


Posted By: Vamino
Date Posted: 29 Nov 2018 at 8:31pm
Daytona 2 is the game that shows if your boards are 100% stable and error free. Boards that I thought were OK wouldn't boot Daytona 2 or would randomly throw various errors. 

I'm with Bonehead, that fault looks to be a CPU board issue. I had a stack that would play Sega Rally 2 but had issues with Daytona 2.

I did come across this guide on my travels surfing the internet, maybe you could ask the author of that guide for some pointers?

https://www.aussiearcade.com/showthread.php/92244-Sega-Model-3-Step-2-0-Repair-Guide" rel="nofollow - https://www.aussiearcade.com/showthread.php/92244-Sega-Model-3-Step-2-0-Repair-Guide


-------------
Insert Coin[s]


Posted By: Kev A
Date Posted: 29 Nov 2018 at 10:20pm
Cool thanks for the help guys, hopefully have a quiet day at work tomorow and i can read theought that guide. Looka like it may be usefull. Interesting you have had stacks that would play SR2 but not daytona, as thats what it was running originaly and apart from a slight graphics glitch was working ok


Posted By: robotech
Date Posted: 30 Nov 2018 at 12:37am
All the naomi boards i have owned i removed the supercap
I dont know what it does as they all work fine without it

Another cpu board shouldent be too expensive unlike the step 2 video boards
Unless you want to put the hours into that cpu board for fun/enjoyment



Posted By: Kev A
Date Posted: 30 Nov 2018 at 9:21am
Originally posted by robotech robotech wrote:

All the naomi boards i have owned i removed the supercap
I dont know what it does as they all work fine without it

Another cpu board shouldent be too expensive unlike the step 2 video boards
Unless you want to put the hours into that cpu board for fun/enjoyment



Its just to provide power to the srams when you change the coin battery, so Sega making things overcomplicated.
To be honest it was a long shot being the only thing in that area that is easily replaced and their tendency to leak I thought it was worth a try.

Bonehead is going to look through his spares to see if he has a spare D2 stack for me, I have ordered 2 srams, but I'm a bit worried about installing them, but then if the boards buggered anyway it might be a good chance to learn.


Posted By: Kev A
Date Posted: 06 Dec 2018 at 5:16pm
Bit of an update here, got a faulty SR2 ROM board from Mo, and swapped the ROMs over to my Daytona board (turned out the ROM board was busted but the ROMs are fine) and whilst I'm still getting a black screen when I first power it on, after leaving it a couple of mins and cycling the power it boots up and plays fine. So I'm a bit unsure what to think. But at least its playable again.



Posted By: robotech
Date Posted: 06 Dec 2018 at 8:38pm
If you have a hot air station the s rams are very easy to replace
You can use that chipquick stuff if not but i would buy one of those cheap ebay hot air stations 505d i think mine is
great tool to have if you are trying to repair surface mount stuff
Worth a try if the boards knackered anyway


Posted By: Kev A
Date Posted: 06 Dec 2018 at 8:52pm
I keep looking at those hot air stations. Glad to hear they work well enough. I have ordered some srams and was going to attempt changing them over using chipquick. But now its sort of working again im kinda hessitant.


Posted By: robotech
Date Posted: 06 Dec 2018 at 11:07pm
Chipquick is a bit hit and miss and the cleanup is annoying as you dont want it anywhere near fresh solder

Buy one of those air stations you wont regret it i use mine all the time now :)


Posted By: Vamino
Date Posted: 08 Dec 2018 at 9:41pm
Originally posted by Kev A Kev A wrote:

Bit of an update here, got a faulty SR2 ROM board from Mo, and swapped the ROMs over to my Daytona board (turned out the ROM board was busted but the ROMs are fine) and whilst I'm still getting a black screen when I first power it on, after leaving it a couple of mins and cycling the power it boots up and plays fine. So I'm a bit unsure what to think. But at least its playable again.



Cool, glad you found out what one of the issues was.

It seems if these boards have not been kept cool then all it takes is a knock for them to throw errors. I had a D2 that I reshelled and when it came to playing it the GPU had a fault on boot up which then disappeared when it warmed up. Money down the drain by just moving the stack!

One thing to be aware of is that Virtual On : Oratario Tangram has additional service menu self test/s not found in any other game. Andy geezer showed me that a while back but I can't remember what test/s they are.

I managed to source a V.O.O.T security board and will get some roms burned when I get a reader/some roms. Andy actually has a couple of Virtual On 2/V.O.O.T security boards in his webshop, so if you are in for the long haul regarding Model 3 then owning a V.O.O.T sec+rom kit may be something that helps track down faults in the future.


-------------
Insert Coin[s]


Posted By: Kev A
Date Posted: 10 Dec 2018 at 11:19am
Cool thanks for the tip, I have ordered a rom burner so that might be an option going forward. D2 PE has additional tests in the service menu, the TGP test and the boundary scan tests, which might prove useful, but I cant get that board to boot.
I have read through that doc the Australian fella made and have found a couple of bits of info there that may prove useful.

This stack has always had an error when running the memory test on ic17, its not clear exactly what this relates to, I had always assumed that this was a RAM on the video board and that is what was causing my weird green lines glitch, however looking at that doc he has experienced a very similar error, and the cause was RAM chips on the video board with completely different IC numbers, he does state that when these chips die complexly the stack wont boot, so I guess its possible that my video board could also be the issue.

IC17 also exists on the CPU board, perhaps this error I get relates to that chip instead. The fella who wrote the doc does mention them specifically as scroll RAM, and indicates these can cause malloc errors on boot, and cause the game to crash.

I have ordered a cheapo hot air rework station and I think my plan is to replace the two SRAMS near the battery (I already have these, and a broken CPU board from Mo)

If this doesn't help I'm going to swap out ic17 on the CPU board with one from the other faulty CPU board and go from there.






Print Page | Close Window