SNK Neo Geo MV-1FZ (MVS) Repair Part 2 (Backup RAM)

The second part of the repair to my SNK Neo Geo MV-1FZ. References to Universe Bios 3.1, and 161 in 1 multicart. The board was reporting a backup RAM error at address 00D00010, written 5555 read B255.
ChipQuik www.chipquikinc...
Fast Striker www.faststriker...

[@jorgesaul2280]

Hello Friend! could you help me? you don't have a neo geo MV-1AX system what happens, is that mine got burned the resistors that go after the jamma connector but for the same reason I can't see what values ​​they are and I wanted to see if you can't pass me that information to repair it thank you very much: I have been investigating all week and I do not get that information.

[@GadgetUK164]

The easiest way to work this out is for you to buy another board of the same model, then measure the components! I don't have the information to hand sorry!

[@AntonioMerino]

hi, I have a mvs 1c, it has an error backup ram error addrees 00D00804 write 0804 read 0814, any advice?, it has a ram problem or a some cut tracks? thanks

[@GadgetUK164]

The fact the address is no D00000 before you got an error suggests to me its problably the RAM chip rather than a bad connection.

[@AntonioMerino]

@@GadgetUK164 So can it be that the ram chip is bad? I have checked all the connections and I have not seen anything strange. Where can I get a ram chip? Any recommendation. Thank you very much for your answer

[@GadgetUK164]

You can switch all the DIP switches up to force a RAM test. When you power on it should say WORK RAM TEST. If it comes up with an error there, that indicates either the RAM is bad, or you have a bad connection, or worst case whatever drives the RAM has failed. The address is the clue that it's most likely the RAM though. You can get a Lyontek or Cypress 62256 from eBay or AliExpress. Just check they are the correct SMD parts and not through hole. eg. www.ebay.co.uk/itm/Cypress-Semiconductor-CY62256VNLL-70SNXI-SRAM-Memory-256kbit-70ns-3-3-3-28/142889455215?epid=15021022940&hash=item2144e00e6f:g:LDoAAOSwCA5bYFe5

[@petersutherland8694]

I’m having similar issues with a consolized board here in the UK. Graphic issues start after 30 minutes or so. Hardware Test Failed message comes up upon reboot, always an 8000 address. Looking for assistance or direction for someone to take a look. I believe it to be either a RAM chip issue or possible trace damage.

[@HCKNEOBOOM]

Hi, what power supply voltage do you use with this 1 slot board? I have mine power with a 5V 2 amps and is currently heating up the power supply. Taking in consideration that I have a Scart to HDMI converter installed too to power audio and video @ 1080p that alone needs 5v 1a. The 1080p mode shuts down after playing for 10 to 15 mins. I believe I need more amps right. Should I try a 5v 6 amps or would that be too much power and damage the board?

[@GadgetUK164]

I currently use a Rasperry Pi 2.5 amp 5v PSU with my 1 slot, and that's fine - always showing ~5.0v. If you are wanting to power that scart to HDMI adapter at the same time I would look for a 3amp PSU. The MV-1FZ draw ~1.3amps with a multicart. It's better to have around 100% more power than you are pulling. A PSU that provides more than 2 or 3 amps wont damage the MVS - all that is important is that it can provide enough current, and that the voltage stays between 4.85v and 5.20v. If its too low it will glitch or crash, if it goes above 5.20v you risk damaging some chips on some MVS boards.

[@HCKNEOBOOM]

Great, I finally got my new +5V 3 amps PSU from Jameco. When testing, the voltage stayed between 4.86v with the Multicard and 4.96v with original cards. Thanks so much for your advise! How do you know this stuff? are you an engineer?

[@GadgetUK164]

No problem! I was only in the hardware industry for about 4 years but that was a long time ago - 1994 ish. Ever since then I've been a software engineer.

[@iphonepunker]

hey I bought a box of Neo Geo MVS boards from ebay i came with 8 arcade buttons and 2 Sanwa joy-sticks i looks like a unfinished arcade system that some one sold off anyways it came with 4 MVS boards 1 fully intact, 1 has 1 chip missing and the other 2 has had so many chips removed they will never be fixed. so my issue is I cant find the chip for the MVS thats only missing one its a "Toshiba TC531024F-5P1" anyone know where i could find this chip ?

[@GadgetUK164]

+Kevin Ayres Are you sure about that part number? does it end 5P1 or SP1? It sounds like might might be the main BIOS, in which case you can program an EPROM from BIOS images on the net, or use a UNIBIOS. Might help if you uploaded a video or some photos?

[@vaughan1427]

bought a 'working' mv-1fz and i got the same error, im going to replace the 74hc32 tomorrow wish me luck :)

[@GadgetUK164]

Vaughan Wellington Good luck! Let me know how you get on! Take your time with it!

[@vaughan1427]

didnt work, tried a few other things and cant figure it out. im pretty good with this stuff but its beyond me, just gonna buy an mv-1f so i dont have to stereo mod it.

[@GadgetUK164]

It is possible there's a damaged trace somewhere around the backup RAM and the 74HC32. =/

[@vaughan1427]

yeah thats what i am thinking i could always just try and solder from the 74hc32 to the ram chips and just hope one of the traces isnt connected.

[@mariopic2625]

y not just cut the legs off the bad chip ? makes ur live so much more easy

[@GadgetUK164]

That's a good point! There are loads of ways to get chips off boards and cutting them is a viable (quick) option. My own experience of doing that has been mixed - On DIP chips its fairly easy, but on SMD chips it can be difficult and sometimes possible to slip through the pin and into the track. I wanted to show a different approach on this video, but you are correct in that its quicker and easier to cut them off =) In later videos I've used Chip Qwik which is even easier, and I might show using hot air in a future video. Thanks for watching and commenting =D

[@jockssolorzano424]

good video..! You lack practical to extract the chip. Greetings friend

[@GadgetUK164]

Thanks! If you watch my later videos you can see I have a lot of practical experience - just a different technique used in this video. In later videos I've used hot air rework station to remove SMD component, and in some videos I've just used chipquik.

[@Invenciblemario]

Nice work, you got a sub!

[@GadgetUK164]

Thanks! Looking back at this video now I realise this was not the best way to demonstrate how to safely remove that 74HC32 chip. What I should have done is lifted one side, used the desolder pump to remove the solder and make sure that 1 side of the chip was free, then just heat all of the pins on the other side. There's risk of track damage when moving both sides like I did there. I was having a bad day (you can tell from how my voice sounds compared to other videos) and as a result I went into this like a bull in a china shop! I also didn't solder the new chip(s) on in a very tidy way at this stage. If you watch some of the later consolization videos you can see where I tidy up all the soldering using some good flux and drag soldering.

[@racer4200]

Nice work.

[@GadgetUK164]

Thanks :) In later videos I tidy up the soldering properly using some flux that's designed for SMD work. Flux is the way to go, you can then just use drag soldering to quickly and cleanly tidy up the connections.

[@olganerd]

My 1fz has an error at address 001011A2, written 5555 read 00C1. how do I locate the ram on the board?

[@GadgetUK164]

See here (Neo Geo memory map) - wiki.neogeodev.org/index.php?title=68k_memory_map It looks like the error you are getting is 11A2 bytes into the Work RAM. It looks like both SRAM chips are bad (work RAM) since both bytes 55 and 55 do not match 00 and C1. That might indicate that its something controlling the WE or OE for the RAM rather than the RAM chips. So it could be something like the Neo-C1. I would start by swapping out the WRAM (RAM1 and RAM2). You could confirm it has a WRAM failure by testing with the Unibios or SMK Dan Diagnostic BIOS.

[@olganerd]

@@GadgetUK164Thanks guys for the useful information. Will get to work on it soon.