Today, after repairing the board, I dumped the PLDs (two secured GAL16V8) from a New Zero Team PCB (by Seibu Kaihatsu).Both dumps have been tested working in GAL16V8 targeting device.
‘frsj8112′ ,one of our finest contributors, sent in a PAL dump from a Dragon Breed PCB (Irem M81 hardware).The device is located @IC48 on CPU board and it’s specific to this game.Dump has been successfully tested on a GAL16V8.Thanks again to him.
Lately, I got a total of 4 faulty Night Slashers PCBs from friends to repair. Due to the fact that these boards are mainly populated by SMCs and customs ICs, a custom CPU and no available schematics, making them less handy to diagnose than some older generation boards. I decided to take advantage of having four boards on the bench and recently started working on them.
Among the 4 boards, I had three different board revisions (DE-0395-1, DE-0396-0 and DE-0397-0) only with very minor differences between each.
– Problem #1: The game was running but with major gfx issues. Most of the backgrounds were just plain while sprites seemed fine.
Piggybacking the 64kb RAMs @ 5E, 6E and 9E successfully restored a lot of the backgrounds but there was still some garbled data, even after replacing them.
– Problem #2: The fourth RAM @ 10E was tested good, as well as the two MASK ROMs @ 8A and 9A where the background data is stored. Touching the contacts around the gfx area with slightly humected fingers revealed a few ones where data seemed missing/corrupted as we could see the garbled pixels slightly changing. These sensible contacts led to a 74F373 @ 12C, a 74LS373 @ 11C and a Data East ASIC number 74. The signals looked healthy on the scope so after desoldering the two suspicious TTLs chips, it was finally the Motorola 74F373 @ 12C that was faulty. Replacing the chip finally led to a perfectly fine looking game.
– Problem #3: FM sounds (synths, generated by an YM2151) were very weak compared to sampled sounds (voices, percussions and other samples, generated by two M6295)
Comparing the audio part with an other board revealed a factory mistake in the row of resistors that connect every sound channel to the amp circuit… They put a 15 kOhm at R17 instead of a 47 kOhm. For a good balanced sound, here are the correct values for them:
-R16, R20 & R21 : 8 kOhm (seen 7,4 kOhm on a DE-0395-1 board revision, difference isn’t perceptible)
-R17 : 47 kOhm (seen 50 kOhm on a DE-0395-1 board revision, difference isn’t perceptible)
-R18 & R19 : 67 kOhm
-R22 & R23 : 10 kOhm
– Problems:
-Game was booting but with some letters staggered.
-Game was crashing along with a vsync issue anytime an ingame screen appeared.
Never had this kind of fault before. The staggered letters could be an issue in the gfx part but the instant crash after an ingame screen was clearly a CPU related issue. Not really easy to diagnose (of course I checked the CPU ROMs and PALs but they were good) so I started focusing on the RAMs, a row of 4 SMC SHARP LH52250. Touching the pins on some of their address lines with humected fingers sometimes changed a few of the staggered letters so I replaced the whole lot of 4 and luckily one of them was the faulty one. Replacing it fixed the letters and crash issues.
ps. I cannot show pictures of the staggered letters as I forgot to take pictures of the screen before replacing the faulty RAMs. To give an example, the name of the character CHRISTOPHER in the player select screen appeared as CHRISTOGHER.
– Problem #1: Board was booting on a garbled screen, randomly with a white or pink background.
This type of issue is due to a problem in the main CPU section. It is a Data East 156 ARM based encrypted CPU and there is not much information online nor pinouts available so diagnosing it is a bit tricky. First, as it worked with the previous board, I replaced the 4 CPU RAMs, but with no change. Also, clock and reset signals around the CPU looked fine with the scope. Then, while probing the pins on the CPU, the game suddenly launched with minor gfx and sound issues but also with half of the controls not responding. I retraced the non working buttons from the JAMMA connector to the I/O custom chip which is a Data East 104. Everything looked fine on the scope. When I turned the power off and on again, I got the same garbled screen but after a few tries touching the CPU pins with the scope, I could sometimes get the game running again (with the same issues) or sometimes a black screen with a message : “CONFIGURATION MODE ERROR”.
All these missing controls caught my attention so I looked closer at this Data East 104 custom I/O chip.
It basically makes the link between every button and the CPU. In fact, it is connected to the data bus and is sending information for all the controls to the CPU. If it is faulty then it could possibly send corrupted data to the CPU which may crash it. For example, that could happen in a lot of Taito boards from the late 80’s, early 90’s: if you plug the JAMMA harness upside/down you plug the 12V signal which normally goes to the audio amp to the controls and it directly damages the I/O custom chip which then send bad data to the CPU, leading to a non booting game.
I reflowed this 104 chip but with no changes so I decided to desolder it. I had a spare Fighters History board running on a DE-0395-1 revision board (same board than this revision of Night Slashers) and at the same location there was a very similar chip with its part number scratched off. I naturally guessed it was the same chip so I put it in place of the 104 on the Night Slashers board. No luck… Even worse than before: I could not have the game starting at all, only the message “CONFIGURATION MODE ERROR” at best.
So I contacted Bryan McPhail, author of the MAME DECO 32 driver and he was pretty sure this version of Fighters History used a previous revision of the I/O chip numbered 75, not 104. That would explain not having the game booting even once with it plugged in. So I desoldered it and put in place a 104 chip taken from one of the working Night Slashers boards as I needed to clarify the situation… And that time the game launched directly ! I also got all the controls working perfectly.
Good find, but now I had only one 104 working chip for two Night Slashers boards. Bryan told me every 104 chip could work as a replacement. This chip is present on these games: Caveman Ninja, Wizard Fire, Rohga, Boogie Wings, Diet Go Go, Double Wings, Schmeiser Robo, Pocket Gal DX and Dream Ball. The two last ones being the only ones I could imagine being donor boards, I put my hands on a Pocket Gal DX board, took the 104 chip out of it to put on my Night Slashers board then got it running with all the controls ok.
– Problem #2: Had a few gfx issues (vertical lines on a few sprites).
I quickly found something by touching pins on the gfx ROMs. Vertical lines seemed partially flickering and disappearing when touching some of the address lines on the MASK ROM labeled MBH-09. These are 512kb ROMs with MASK pinout so I burned the matching content on a 27C400 EPROM and tried piggybacking it. It resolved the problem so I put a socket and plugged it as replacement.
– Problem #3: Had some sounds issues. Some voices/samples were missing and replaced by junk noise. One of the two M6295 voice generating chips @ 12M had previously been badly repaired and a pin was very near to fracture. Tracks #14 & #18 on the board were broken by the previous repairer and replaced by two wires going from the M6295 to the MASK ROM @ 14L. I removed the serviced chip and these two wires. In order to replace the missing tracks, I inserted tiny pieces of wire in the holes below the chip, bended them and soldered them in.
You can see here how they were broken on track #14 and how I fixed them on track #18:
And here is how it looks after a new chip in place:
Part of the voices were back but some junk sounds were still audible. While checking the other M6295 chip @ 13N, I found a signal that seemed strangely inactive on an address line which goes to the MASK ROM @ 15L where these sounds are stored. I piggybacked the ROM with a burnt EPROM of the same content but nothing changed. Suspected the OKI M6295 so I replaced it and that fixed the issue. Everything is fine now.
– Problem: Had some sounds issues. Some voices could be heard repeatedly at unintended moments. For example Christopher was saying “I take that !” repeatedly and randomly.
Found an I/O line on the M6295 @ 13N (pin #37) with no activity. This goes to the 104 chip but here there was no continuity with were it is supposed to go. There was a bit of corrosion around the M6295 and a closer inspection of the area revealed a broken hole connected to the track of pin #37:
Only this side of the hole was damaged so I inserted a tiny piece of wire on the other side, bended it here and soldered both sides:
That worked. No unwanted voices constantly repeating anymore.
In the past days I’ve dumped the PLD ( a secured GAL16V8 marked ‘315-5915’) from the drive board of Sega Model 2 CRX games.Chip has been kindly provided by ‘krb’ who also successfully tested the dump on his Sega Touring Car cabinet.Thanks again to him.
For the uninitiated the Irem M92 is an arcade platform introduced in 1991 by Irem.Technically speaking the system is made from a top and bottom board, the top (main) board is common across the games, but the bottom (game) board can vary game to game.Each game has an encrypted sound cpu.Here are hardware specs:
List of games on this platform:
With these premises I begun my troubleshooting on an Undercover Cops and GunForce PCBs.
I bought the first as faulty:
Seller warned me about severe corrosion in some area of PCB, this was confimed once received the board, it seems like the board has been stored in a very humid place :
Anyway, once powered it up I got this:
Game actually played blind.I noticed that if I pressed the PAL marked “M92-A3-M” @IC11 graphics were restored in a bad way though:
This was not a case since this PAL was located in the corroded area so I decided to remove the socket.Underneath I found this scenario:
After cleaning from corrosion, I checked all the connections and found a missing contact bewteen pad of pin 8 (an input of the PAL) and its trace which I promptly patched with some kynar wire:
With this fix graphics were almost good but there were jailbars all over the screen:
Again, pressing a specific area of the PCB restored graphics temporarily so I started to look around until I was able to locate the cause of that issue:
Several pins of a custom ASIC on the video board were lifted.Since the pads were corroded too,a reflow was not enough to ensure a good soldering so I decided to reinforce it using some pieces of AWG3o wire :
This fixed this first M92 board completely:
So I moved on the GunForce PCB:
First thing I noticed after my visual inspection was the lack on many electrolytic capacitors in the audio circuit:
Board booted up but video as disturbed and a rustling sound was present on backgorund :
Usually this issues are caused by increased ESR of elecrolytic capacitors which inject disturbs on video circuit as well.The previous repairer thought about this and therefore removed all the electrolytic capacitors but this didn’t cure the problem.But He forgot to check the main amplifier:
Probing in AC the +12V line with my scope confirmed that ripple was present:
If I excluded the +12V from my supergun the video became normal and no more rustling sound.So, since on PCB there was no other component connected to this supply line, the amplifier was most likely the culprit.I removed it :
After fitting a good amplifier and all the missing capacitors, the video and sound were perfect but other two issues were present : the controls didn’t work and sprites were glitched.As for first issue, it was due the fact someone replaced a couple of custom resistor arrays with normal 4.7Kohm ones:
Like the ‘8M472J221J’ part name said, the original array is a mix of 4.7KOhm and 220 Ohm resistors.Not having other spare parts, I opted for a custom solution keeping the 4.7Kohm array and mounting some SMT 220 Ohm resistors on solder side:
This worked perfectly, controls were responding so I moved on to troubleshoot the sprites issue:
Sprite devices were four 2Mbit MASK ROMs (compatible with 27C020 EPROM) on video board:
I reprogrammed a 27C020 for each ROM file in order to do piggybacking.When I did it on the one @IC41 glitches vanished.I removed the device:
My programmed warned me about a bad contact on pin 31 while I was reading it:
I socketed and replaced it :
100% fixed!End of this double Irem repair.