Naomi RAM and SRAM Questions

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OldFoo

Naomi RAM and SRAM Questions

Post by OldFoo »

Hi again.



Picked up my two Naomi games from the mail today and while I've had some fun with them afterwards, there's a couple of questions and concerns that I have on my mind.



Firstly, I set my Naomi to Free Play since I don't have a coin harness nor do I plan on using one yet, but whenever I insert a cartridge or swap my two games around, the SRAM defaults back to 1 credit = 1 coin mode. It's rather irritating to keep going into the test menu to change it. Anything I should be doing? The CR2032 batt is working fine BTW.



Secondly, when I first took my Naomi out again having left it unplugged and unused for a while, I put a cartridge in and it showed serious graphical glitches and slowdowns even on the BIOS. I thought the cart was drawing a little to much power so I removed it, turned my Naomi on yet it still did the same errors. Tried the other cart wth the same problems. I tried cleaning the IPL's legs and making sure that all wiring was connected. I cleaned any dust out of the ROM's sockets and the IPL's socket still nothing. Then once it wouldn't even boot. I left it for a while and later I plugged in Virtua Tennis, and it booted fine with no errors at all, until the game played, which there was some pixels and errors. Left it for a while and since then it's had no problems at all.



I'm seriously worried there's a fault on my board since I know they're not cheap to fix. I have no means of testing the voltages, but I'd assume a PC powersupply only sends the current out when voltages are stable, but then again I'm a n00b with that. Before Andy said that the RAM chips might be going, but the test says they're fine...



Thirdly, does EPR-E-21576 work with the GD-ROM? If so, network? *shot*
OldFoo

Post by OldFoo »

The SRAM resetting after changing carts is normal and, by far, unavoidable. That BIOS will work with the GD system. As for networking, I will assume you mean 'linking' through optical cables for multiplayer as the ethernet port is basically only used for one purpose that is banned on these forums. That is supported by certain games rather than the BIOS and they need communication boards for each system linked.
OldFoo

Post by OldFoo »

I have no means of testing the voltages


A cheap digital multimeter from an electronics or car store will be more than sufficient, and is very handy in the arcade hobby. Plenty of guides out there to get you started in their use too.


I'd assume a PC powersupply only sends the current out when voltages are stable


It'll send voltage so long as there isn't a short, in which case a fuse will blow or circuit breaker will trip. Only a few enthusiast PC power supplies will shut down or warn you if the voltages are unstable.




Thirdly, does EPR-E-21576 work with the GD-ROM? If so, network? *shot*


E will work for all DIMM units. The BIOS guide says you need F or higher for Cabinet Linking (via the optical cables). It'd be recommendable to get a Japanese BIOS anyways, if you want 100% game compatibility. I keep bumping into compatibility/region issues myself and a US E BIOS.
OldFoo

Post by OldFoo »

I have to ask about this graphical corruption as it still goes on. Like before it will mess about for a while before suddenly working, but will start the problems after so long of waiting. Does anyone know anything about this?
OldFoo

Post by OldFoo »

Get a multimeter and check that the voltages are right. If it's a power supply troubles, it's easy to adjust the power supply into the right spec.



However, since it's doing it after warms up, it sounds like problem with the mainboard. It's probably not worth fixing, as prices on Naomis seem to be dropping (at least on US eBay), making it easier to just get a new one and storing the old for parts.
OldFoo

Post by OldFoo »

tom61 wrote:Get a multimeter and check that the voltages are right. If it's a power supply troubles, it's easy to adjust the power supply into the right spec.



However, since it's doing it after warms up, it sounds like problem with the mainboard. It's probably not worth fixing, as prices on Naomis seem to be dropping (at least on US eBay), making it easier to just get a new one and storing the old for parts.


It's very strange, it hates to work 100% after hours upon hours, but after so many attempts within an hour it'll work again..



Easy for you to say, I'd rather fix it if it's cheaper, I don't have money to draw out of the eyither XP
OldFoo

Post by OldFoo »

Usually professionals charge $60+ an hour with a one hour minimum(I.E. if it takes less than an hour you still have to pay $60) to work on electronics, and working Naomis are going for that and sometimes cheaper on eBay.



It sounds like a bad solder joint to me, but reflowing the joints on SMT may be a bit out of your range of capability. It could be damage to the PCB itself (cracked), or it could also be the already mentioned RAM going bad (partial failures that don't show in diagnostics are possible).
OldFoo

Post by OldFoo »

tom61 wrote:Usually professionals charge $60+ an hour with a one hour minimum(I.E. if it takes less than an hour you still have to pay $60) to work on electronics, and working Naomis are going for that and sometimes cheaper on eBay.



It sounds like a bad solder joint to me, but reflowing the joints on SMT may be a bit out of your range of capability. It could be damage to the PCB itself (cracked), or it could also be the already mentioned RAM going bad (partial failures that don't show in diagnostics are possible).




Man that sucks.. :smt010



EDIT: Hmm, actually, if power can affect it, other than voltages, can the type of cable used for the power affect it? I didn't think too much when I wired my JST connectors up, and I'm betting the Naomi is getting the voltages just not enough amps, fair assumption? I did only use some thinish wire, like for audio applications.
OldFoo

Post by OldFoo »

A quick test supported my theory of ampage being low, since using thicker wires results in it booting and playing fine for a little while, unlike before where it would already start showing defects
OldFoo

Post by OldFoo »

If you're using wires that small, I'm surprised it didn't catch fire. Use wires about as thick as the wire used to power drives in a computer.



As the wires heated up the voltage likely dropped, you should have been able to measure it. When checking faulty stuff, check when it's good, and again very soon after the fault occurs.
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