MV1FZ won't save scores (not battery)

Just done the battery mod, disabling the charging circuit and putting in a cr2032, but my neo still won't save scores when it's turned off. I think I can see what the problem might be but want to make sure. When I removed D1, D2 and R3, I noticed some brown spots under D2 and more importantly D4. This makes me think that D4 might have burned out. Would this interfere with the battery circuit and stop power from getting to the ram? If so, does anyone know where I can source an HRF22 Schottky diode?




(Not a picture of my board, just a picture to show which components i'm talking about)

Just to be on the safe side, did you check volt. across the battery had 3V? Probably a new battery, but start there if you have a multimeter. As far as the brown residue, it's probably flux, and get some pics if you can.

Right, checked the voltage, has 3.25v across it. Also got a picture,

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Not very good i'm afraid but you can just about see the brown spots i'm on about. To be fair it does look like flux but if it's not, unfortunately d3 also looks a bit suspect.

Had another thought though, would it matter that i've been testing it with an 111 in 1 cart? Maybe something in the way it's coded means scores don't save?

try clearing the backup ram first. Also don't forget that it only saves 8 games.

You cant save high scores on the 111 in 1 carts.

Right. Cheers everyone. Good to know there's nothing wrong with my board. I'll go an check with another game to be sure..

Just checked with my league bowling cart an it works Whoop! (Unfortunately that does mean i'm gonna have to shell out £80+ if I want to save my strikers 1945+ scores but you can't have everything I spose..)

Hi, sorry for hijacking this thread, I dont seem to be able to create my own threads =/

Anyway, I have a MV-1FZ that initially 'appeared to work', despite some games glitching and doing wierd things - time out on Metal Slug at start etc. Anyway, I disconnected the battery in order to replace it (no corrosion or damage to the board at all), and after disconnect and power up I got the backup ram error. I assume because the RAM is wiped from complete loss of power that it has a BIOS routine to check the backup RAM before initialising it for use etc. Anyway, the error was at address D0000000 (sorry if ive missed a zero, all zeros after the D) with wrote 5555 read B255, which I assume is RAM3. I've checked continuity from other threads ive found for all connections from all the RAM chips (2 work ram, and 2 backup ram) and all looked fine. I've today replaced the 62256 chips nice and cleanly with no damage anywhere and minimal heat etc. Now I am getting the same error but at address D00000010, same value wrote 5555 read B255. I also replaced the RAM4 IC just incase it was that - same problem.

One thing I cannot check continuity to is Q1 referenced in this thread in the table of connections:- http://www.neo-geo.com/forums/archive/index.php/t-205559.html

The underside of my MV-1FZ board has no silkscreen markings for components etc =/

Help!! Should I consider replacing U17 and U8? I've got a logic probe but not really sure what I need to check, I believe U8 is an OR (74HC32A?), not sure what U17 is (74LS245?)

Also... I should explain, using Unibios I can skip the backup RAM error and for the 'most part' things work. By that I mean that I cannot play Metal Slug games typically, it gives an exception running as europe region, but if I change uni region to US the game then plays but has zero time left, so your player keeps dying etc. Many other games work fine without a problem. I am attributing the glitches to loss of proper backup ram facility.

These are the SRAM chips i've used - should they be OK?

http://www.ebay.co.uk/itm/LYONTEK-L...Supplies_ET&hash=item51afc8da54#ht_375wt_1399

Sorry for the post count - I am not trying to spam here. I've made some progress in the last 10 mins. I found this thread:- http://translate.google.co.uk/trans...ay.free.fr/?slot-mv1fzs-backup-ram-error.html

Which basically gave me the bit of knowlege I needed - that the 74HC32 is an OR gate as I thought, and that using logic probe I could test easily. The 2nd OR gate on there has a low and a high as inputs and is outputting a low. Things are starting to make sense now. I've ordered a 74HC32 and I will post once ive fitted it. Fingers crossed this sorts it. I suspect the backup RAM was faulty anyway as I was getting the error at 00D00000 before replacing the RAM and now at 00D00010. Incidentally, i've found the datasheet for that LY SRAM I fitted and the pin outs are fine. It's 55ns but that should be a problem I think!?!?

Love this forum btw, its a god send - it really is! Trying to find tech info on the neo geo is pretty hard at best and there are no circuit diagrams or schematics that I can find. If anyone has ANY diagram please let me know where I can get a copy as I am working blind here =P

The 74HC32 fixed the board =)