Neo Geo MV1FZS - Timing Crystal Issue [FIXED!]

[Flinnster]

Just picked up this non-working MV1FZ (actually a 1FZS). Other than the interesting hot-glue work and the odd eprom BIOS (its just the normal MVS Bios, not even a unibios burn sadly) .. it's the onboard battery that looks like trouble:

I'd read elsewhere that these newer coin-cell type batteries are far less likely to leak compared to the old drum batteries, so needn't be replaced on these single slot boards.
I think I'm going to call 'bu11sh1t' on that one....

So after some snipping, removing of hotglue and being spat-at as I tried to desolder the thing (hmm.. some eye protection would be a good call next time...), I managed to clean the area up.
Well it took a load of cleaning.. but got there in the end.
Sadly the timing crystal has been totally nuked, the sacrifice for the nearby chemicals clearly!

So, without battery or crystal, it now boots to the greenscreen. The 'WORK RAM TEST' functions if I throw all the dip switches, but it never gets to the grid pattern or test mode:

Soooo... replacement crystal time, and then I'll do the battery mod to fit a CR2032 non-charging cell.

Anyone know where I can get a suitable 32.768Mhz timing crystal?
(It's the small 1cm long, silver cylinder type).

Flinnster2018-06-26 23:21:08

 

[stevebm1]

I think I might have one mate,but I'd need to check first

 

[Ace`]

10 for a quid http://www.ebay.co.uk/itm/10Pcs-32-768KHz-32768HZ-Crystal-Oscillator-2-x-6-mm-TOP/272041594203?hash=item3f56f14d5b:g:nVwAAOSwSHZWg4uU

 

[Flinnster]

Cheers for the super quick replies!

I'd been looking on Farnell and there are some that are 15-20p each (but with a 4 quid 'handling charge'!).
Also not sure about the various ratings.. or if they even matter?
6-12.5pF / 20PPM / etc..

Load Capacitance: 12.5pF.
Equivalent resistance: 35K?.
Frequency tolerance: +20 PPM.
Flinnster2018-06-22 20:12:08

 

[robotech]

I bought some from e bay I have repaired a few mvs boards with them
ill send you some if you send me your aderess

 

[Flinnster]

You are a true gent, sir! I will pop you a pm

 

[Brettster]

I guess that Xtal is just for the on board clock, if you have a unibios it will bypass it anyway and you can see if the rest of the board works ok

you can also burn a Diagnostics bios that will help diagnose issues with the PCB

 

[robotech]

yes the crystal is for the clock chip
I have never had a unibios to try it bypassing the calendar error I had watched videos about the diagnostic roms but never had to burn any

I am no expert though learning through reading and watching other peoples repair videos

 

[Flinnster]

Yeah no unibios here, although with this pickup and the eprom bios rather than the standard, perhaps I could do a cheeky swap on that

I understood diagnostic roms are different and have to go in a game cart right?

Finally is it possible to get past the green-screen without a unibios if no crystal is present? (What I'm trying to say is.... is the green screen due to something else, like trace non-continuity etc.. rather than the lack of crystal itself?)

 

[pulstar]

I understood diagnostic roms are different and have to go in a game cart right?

There are two different diagnostics roms. One goes in place of the bios and does a range of hardware tests. The other is put on a CHA board and is only needed if you want to test the Z80 sound system (you still need the one in the bios to do these tests).

Finally is it possible to get past the green-screen without a unibios if no crystal is present? (What I'm trying to say is.... is the green screen due to something else, like trace non-continuity etc.. rather than the lack of crystal itself?)

If the issue is just due to the calendar the Uni Bios should be able to get past that and boot properly.

 

[Flinnster]

Thanks for the info! I really do need to get myself a Unibios sorted for these kinds of things don't I!

Huuuge thanks to Mr. Robotech though! An envelope of repair bits fell through my letterbox today!

So this evening I got to work, and yep - just as described fitting the new crystal brought the deck back to life, straight into the test grid!
So I did the battery mod, and so far settings and time seem to be saving properly (probably need to do a bit more testing over the coming weeks on that one though!).

Sadly on the test mode I discovered P1 button D was totally dead, along with P2 Left & Right.
Initially I thought these may simply be due to the legs of components near the edge connector being bent over and actually crossing / shorting out.
Straightened them up but no joy - clearly the battery leak had done it's usual trace damage.

Inspecting the resistor arrays and traces, I could see the 'bus' next to the battery leads up to the NEO-C1 chip from the resistor arrays near the input pins. This is where this NeoGeoDev wiki page detailing the pinouts proved to be incredibly useful. I was able to trace the exact pins for P1 button D, and the P2 joystick movements.

And lo behold the traces from these pins are the 3 nearest to the battery on that 'bus' going down to the bottom of the board!

Re-patched them in suitable places on the underside of the board where the grey insulation pad would have been, and boom - one fully working MV1FZS motherboard

Another one saved!

Next up, I'm going to try doing a stereo mod on this board.
I've seen something for consolised versions, but I'm not sure if it knobbles the standard jamma audio (Ideally I'd like something that is mono via jamma, but I can send stereo out of a headphone jack).

Flinnster2018-06-26 23:40:35

 

[jase38]

Awesome work and a great write up.

 

[robotech]

Glad you got it working robotech2018-06-26 23:54:03

 

[Brettster]

Great work

 

[Flinnster]

Well thanks to Jase for sending it over for surgery, and Robotech for the replacement parts!

Non-kynar wire is a bit suspect for soldering to some of the via points to be honest (another thing to add to my shopping list along with a unibios).
I hot-glued the crystal and patch wires afterwards to make sure they stay safely in place.

Still looking into stereo mods

 

[vids]

hi i have a none working MV1FS board would you be able to take a look at it for me please ?

cheers gav

 

[Flinnster]

Hey, well let me know what it is currently doing and I'll see if I can advise

I have fixed a couple before. Jon MooMooTown has one of mine in his Astro City.