Neo Geo MVS 4 Slot pcb repair

One last repair in 2016, I was going to take a break but couldn't resist having a look at my newly arrived Neo Geo 4 slot.

This was a quick 'buy it now' on eBay, described as untested which usually translates to tested and didn't work. The price was good though so worth a gamble. First thing I noticed after separating the two layers was that the battery had leaked and been removed by the previous owner.

After cleaning it all up and patching the three traces directly under where the battery used to be I powered it up. Slots 2, 3 and 4 worked fine apart from no sound and slot 1 worked but with vertical lines through the sprites.

 

This very helpful page told me I have an issue with a C rom data line. Then using the pinout found here I was able to find out which line exactly. I removed the case from Nam 1975 and used dip switch 8 to freeze the system on the image above, then using a wire connected to ground I touched it to each C rom pin at the cart edge connector. Thanks to the vias above each pin I was able to access all C rom data lines on one side of the pcb and didn't have to worry about the PRG pcb getting in my way.

Going through each pin I found touching each pin to ground made the image worse until I got to CR16 which made no difference to the image.

I then followed the CR16 trace to find the break, it was on the top pcb next to slot 4 just before a via.

I ran a patch wire on the bottom and held it in place with a few blobs of hot glue.

That's slot 1 sorted now just the sound issue remained, bad caps are apparently a common issue on 4 and 6 slots for some reason so I started there. After recapping the entire sound section stereo sound returned, I checked the caps and a good 70% of them were way out of spec and had really high ESR.

The only problem now was I wasn't getting audio from the mono pin of the motherboard. This turned out to be an issue with the MVS to Jamma adapter I was using. It has the MVS mono pin connected to the JAMMA speaker + pin which would be correct if MVS motherboards output mono audio, from what I can tell most don't. I believe the only MVS pinout boards that do output mono have a stereo / mono switch on the motherboard which neither my 2 slot or this 4 slot do.

It's not a huge issue as I plan to use it in my JAMMA cabinet which has a stereo harness but for the supergun and testing I'd like to be able to test sound so I modded the adapter.

First I lifted and isolated MVS pin 11 (mono) because if I do ever connect it to a board that outputs mono I don't want it outputting mixed stereo and mono on the same pin.

Then I flipped it over and connected two low ohm resistors (10 ohms as it's what I had to hand) from stereo L and R to JAMMA pin 10.

Repair complete.

Momoko 120% export version (prototype?) found / repaired

I've had this pcb ten or more years but never actually got as far as looking at it or testing it, why you ask?

This is why, football games go in the scrap pile and that is where this one was heading until I decided to do a romident just to make sure it wasn't a good football game (if such a thing exists).

Momoko? what the hell is that... a little girl with a gun in a burning building shooting aliens that sounds amazing!.

Time to find the pinout, both klov and a post on the aussie arcade forum say it's not JAMMA and there's no JAMMA markings on the board also someone has previously soldered to it. There's no pinout online though and very little information in general, eventually I found a pdf of the manual here. Which confirmed that it is JAMMA.

On power up I had no sync, on closer inspection half the sync pin was missing and it was about 1mm too short to touch the edge connector pin.

I've had to do a repair like this before on a DK Jr pcb (posted a while back)

A little too much solder but it works and isn't in the way of the edge connector.

Powered up and got this screen and a clicking sound where the watchdog was constantly resetting the cpu.

I was dreading having to do any work on this board because every single chip apart from the eproms has had it's markings sanded off, not to mention the huge amount of factory mod wires.

I was able to check every socketed chip and luckily the markings are still on the pcb itself, the 6264 work ram failed in my chip tested. I fitted a new one and...

Bingo! (hmm pink text?) :)

After a quick blast I dumped all the roms and checked them with romident and the two program roms came up as unknown. After trying the game in mame I instantly noticed that the screen with the age of the girl was in japanese but on mine it was english.

 

Jaleco not only translated what little japanese there was in the game they also improved the text colour making it easier to read.

It's amusing that Jaleco thought they had a market for this game outside of Japan and that they didn't even rename it or change the title screen.

I suspect this board is a prototype because of all the sanded chips / mod wires and the fact another hasn't been found yet. I wish I could remember where I got it and find out some more information. I think I got it from when I cleared out a local operator as they had quite a few treasures.

Maybe when the work ram died and the pcb was stored someone later came across it they marked it as 'football' as it does resemble a world cup 90 board and that's why it's got football written on it?.

Anyway that's enough speculation and rambling, this version will be showing up in mame soon.

Exerion pcb repair

This game had the wrong colour background and vertical lines through the background and sprites. After checking a few fujitsu ttls with the logic comparator it flagged a 74LS157 @ F11.

This was confirmed with the logic probe and chip replaced with a socketed and a new LS157.

Repair complete.

Multi-Wars pcb repair

This board was removed from a Gayton games upright cabinet. They made bootleg cocktail and cabaret cabinets in the early 80s, they're probably best known for their Pacman bootleg 'Munchyman'. They made quite nice cabinets with G07 monitors and mirrored marquees / bezels that you'd expect to see on a pinball machine rather than a video game.

Anyway onto the board this is a bootleg version of Uniwar S by Irem, this hack / bootleg seems to be pretty rare as it's not in mame (see what I did there?) :)

After making up a jamma adapter I was greeted with this

The text was repeated, some missing and repeating sprites no starfield and no explosion sound. After a bit of poking around I found a bad 74LS86 @ 3B. I've found if there's a fujitsu ttl with a cap or wire soldered across the top of it stopping you from easily connecting your test equipment to it you can pretty much guarantee it's bad.

This fixed all the issues except for the missing starfield and explosion sound, looking at the galaxian trouble shooting manuals (as the hardware is similar) suggested these two were related. I wasn't finding the same ttl the galaxian manuals were pointing to though. A big thanks to Macro for pointing me in the right direction, it turned out to be a bad 74LS74 @ 2D.

The strange thing is once I removed it and put it in my abi chipmaster chip tester it passed. I installed a socket and a new chip anyway as I knew it was bad when it was in the board from what I was seeing on the logic probe.

Repair complete.

Super Wild Card RAM upgrade part 2

A big thank you to Porchy for sending me two 18V10 gal chips so I was able to continue the SWC ram upgrade. Everything I needed to know and the two 32mb gal files are all in this thread, I basically just copied what was going on in rcade's two pictures. His pictures are of a later revision to mine known as the Goldstar version due to the Goldstar floppy controller chip where as mine has a Motorola floppy controller.

The pcb layouts are a little different but the modification is exactly the same. 3 lifted pins, 3 wires and a single cut trace. I've also upgraded the bios to the latest version (2.8CC) since last time.

Loaded a 32mb game using my old laptop and....

 Success!

The floppy disk drive is starting to fail so I might look into replacing it with a floppy emulator that uses a usb stick some time in the future.

Super Wild Card RAM upgrade (SNES Copier)

I opened this up initially just to remove the battery before it leaked but noticed two empty spaces for more ram which would take it from 24mb to 32mb. Would it be a case of simply soldering in two more dram chips?

There isn't much information out there but a google search did find some forum threads that suggested I'd have to replace or reprogram the two PAL/GAL/PEEL chips (PEEL in my case) and also cut some traces / add some wires so the machine could make use of the extra memory.

The ram looked familiar, I checked some old pc ram I have and sure enough one stick (dated 1992) with the exact ram chips on it, even the same manufacture perfect!.

 Added some chip quik to two of the chips and yoink.

Two rams added to the SWC and two decoupling caps (one on the underside of the pcb).

Time to power it up and make sure it still works.

It works and how much ram does it see..

Woot! I need to do some more testing but it looks like the upgrade was a success.

UPDATE: Looks like I need to replace the PEELS and do the wire mods as loading any 32mb rom results in a black screen, to be continued.

Elevator Action PCB Repair (from hell)

This pcb was bought from ebay years ago as untested when it arrived and I saw the state it was in it was stored away and been stored ever since. More recently I got a working Elevator Action pcb in a job lot of boards which reminded me about this one and having a working one could help narrow down which were the faulty layers by swapping on to the known working board.

Out of the five layers only the second one (sound board) worked correctly, even the tiny rom board on top was dead.

I didn't do a good job of documenting this repair as it was spread out over a week or so while waiting for parts and between doing other jobs. From the list of parts I had to replace you can see it was a bad one though, if I had known how many parts were bad and how long it would take to get running it would still be in storage or maybe the scrap pile. :)

 This is most of the bad chips, I forgot to save the 40193s.

The board had obviously had a nasty power spike or been hooked up incorrectly at some point as it wasn't just fujitsu ttls (although there were quite a few of those too). The ribbon cable that joins the security mcu board was even melted and had to be replaced.

I managed to reuse one of the original 40 way idc connectors but the other split so I had to replace it with a new 3M one. The originals are much nicer quality than the 3M but it does the job.

Here's a complete write up of every part replaced for those interested.

Top PCB (Small rom pcb)

3x CD40193 4bit counters which I had to order. UC10,11,13

Layer 3

2114 RAM - IC17,18

74LS157 - IC1,13,14,76

74LS86 - IC28,42,70

74LS374 - IC24,34,99

74LS10 - IC54

74LS74 - IC7

Layer 4

74LS138 - IC76

74LS157 - IC77

74LS32 - IC94

74LS74 - IC87,89,90,97

74LS374 - IC8

6116 RAM

Layer 5 (Security MCU / CPU board)

74LS245 - IC19

Ribbon cable

Repair complete.

Space Invaders PCB Repair

I've had this Space Invaders board a while along with another one but kept putting off looking at it. Mainly because my 8080 fluke pod has never worked right and even when I thought I'd fixed it and had it passing self test it would still fail to do anything outside of self test.

Anyway lets see how far we can get without the fluke.

This is basically the screen you get when the reset circuit isn't working on the power supply but as I am using a jamma adapter I've tied the POR (power on reset) to ground via a resistor and it still didn't make it past this screen even if I pulled the reset pin high.

I already knew the cpu and eproms were good from when I had a working board so I moved onto the logic as even if any rams are bad it should still boot. The HP comparator flagged a 7486 @ A4 saying output pin 8 was bad. I checked it with the logic probe and it was stuck high, shorting it to the input pin next to it and the board booted.

I replaced the 7486 with a 74LS86 which worked fine and it booted every time. The problem now is the screen is a complete mess so we have at least one bad ram. I tried the two different test roms but couldn't work out what either one was reporting as bad.

So I did the old trick of removing all the roms and booting to get lines on the screen then shorting pin 7 of each ram to ground until things look better.

I ended up replacing two rams and using some turn pin sockets off of a scrap bootleg board.

It's alive!

There was just two problems that remained the missile shot sound was very high pitched and the launcher exploding sound when you die was missing completely.

This very helpful page suggested a bad 4006 but it was actually the 4030 chip next to it @ P5.

The motherboard is a L000 revision that I couldn't find anything online about so I had to figure out how to strap it for 2716s myself (Intel type not TMS). It's basically the same how you strap other revisions but S1 (A9) is not connected by default and there's a few more pads on this one.

Repair complete.

ZX Spectrum +2 Issue 3

Another revisit, I've covered the ghosting mod already and mentioned the mod to separate the audio from the video. I never snapped a picture before though and doing the mod again today I couldn't remember where capacitor c31 was.

So here's a blurry picture for my future reference or anyone else that prefers to see a picture of the mod rather than schematics with ms paint edits. :)

Transistor TR4 on the right of the RF box needs to be turned around on issue 3 motherboards too which this was.