repair log – Page 2 – JAMMArcade.net

Ikari Warriors repair log #1

Oct 232015

I recently repaired a friend’s dead Ikari Warriors PCB.

It had a black screen on boot with no sound.

This game is a bit tough to diagnose as it is composed of 3 PCBs mounted on each other. Fortunately I had another working Ikari Warriors PCB so I could swap boards in order to track which board(s) were faulty. Top board and middle board were tested ok on my working Ikari so, fortunately, only the bottom board was faulty.

Here is a picture of the faulty bottom board with the faulty chips I replaced in red. I’ll explain every step below.

1. There was something that was avoiding the game to boot on that board. First, in order to reduce the field of investigation, I disconnected each of the 3 connectors on my working Ikari to see when the game was booting or not. It was booting only with the two bottom connectors on, the one above is only related to the sprites and doesn’t prevent the game to run. So I needed to focus on and around these two bottom connectors. I checked the signals on every pins to track a possible missing signal. After comparing the signals, I found one that was “floating” on my faulty board and was pulsing on my working board. This was connected to pin 9 of the 74LS367 (marked 1 on the PCB picture). Piggybacking a working chip on that one bring the game booting back again !

2. Well, the game worked but the characters had missing legs and were always looking down whatever movement you did, enemies had wrong visuals and background scrolling was jerky…

As previously seen, the sprites are related to the upper connector. I started to check the signals on the upper part of the board and quickly found a 74LS273 (marked 2 on the PCB picture) with a seemingly dead output (my working board confirmed this). Piggybacking the chip with a new one bring back the characters’ movements and visuals. I still had the jerky scrolling though…

3. This one took a bit longer as I had no real idea where to look on the board for the chip that was responsible of this jerky scrolling. After more than an hour, comparing signals between the working and faulty boards, I found a suspicious signal on a 74LS86 (marked 3 on the PCB picture). This was indeed a dead output (pin 6). Piggybacking a good chip on it bring back the smooth scrolling.

As an example, here is what the signal looked like on the pin 6 of that 74LS86 before and after replacement.

Board is now fully fixed.

Edward Randy repair log

PCB Repair Logs, Repair Logs 3 Responses »

Sep 042015

I got an Edward Randy with a black screen (but partial sound).

After a few checks with my scope, I quickly found a PAL @ location N5 with no signals on all of its outputs (BUT signals on its inputs).

As PALs from this game are not available yet online, I looked for other games that possibly shared the same hardware/system in order to try using a similar PAL.

And yes, that system is listed as “Data East Caveman Ninja Hardware” in MAME and some of these games got their PALs dumped. It was the case of Caveman Ninja and Robocop 2 that shares an almost identical PCB layout than Edward Randy (there are only a few differences in the GFX ROMs part).

So I burned the PAL at location N5 from Robocop 2 and plugged it on my Ed Randy board and here is what I got:

Well, at that time I was thinking it was due to an incompatibility between Robocop 2 and Edward Randy PALs and I temporarily gave up, waiting to get a dump from a working Edward Randy to be sure…

Then Shoestring confirmed me Caveman Ninja and Robocop 2 PALs @ N5 were strictly identical. It leaded him to believe that perhaps they are all common to each other and maybe there is a different problem with my board, which pushed me to have a look back at my board for possible other faulty chips. And he did well…

I started looking for other issues on the PCB and noticed that bending the board made the garbled graphics changing, even making them better looking at some point.
So I suspected the two SMC Data East customs labeled “55” having bad solder joints and reflowed the solder on them.

It then went way better. I had clean backgrounds in game, full intro with clean texts and pictures, title and Data East logo appearing (didn’t have all of that before) but no sprites in game. I noticed a square on the bottom-right corner that seemed containing garbled parts of sprites.

I then managed to find where the sprites part was located on the board and found two 6116 RAMs @ locations N9 and M9 that had suspicious signals on their data lines (pulsing but weakly and at low voltage). Piggybacking a known good working compatible RAM made parts of garbled sprites randomly appearing on screen.

I then desoldered one of the two RAMs (at location N9). With no big surprise it was tested bad on my programmer. I soldered a socket and put a new RAM in place. There was still no sprites but the garbled square on the bottom-right corner was not there anymore. Data lines on the new RAM were looking pretty much better though with strong pulses at 5V. The RAM located at M9 still showed weak outputs so I replaced it with another good known RAM:

Then sprites magically appeared !

Only one thing was remaining: the voice generating chips (2x OKI M6295) were missing so I replaced them and got the sound fully working.

I played the game several times since that and it is working perfectly.

Rastan repair log #2

PCB Repair Logs, Repair Logs 1 Response »

Aug 302015

I bought a dead Rastan PCB for a fair price on a forum.

All I got was a screen with garbled graphics on boot:

Luckily, schematics are available online for this board. Anyway, I spent hours with my scope trying to find why there was no activity at all in the CPU area. I desoldered the two RAMs and the 68000 (all were tested OK as well as the ROMs).

Next, I desoldered the 2 PALs that are involved in the address decoding (labeled B04-09 @ IC11 and B04-10 @ IC12) in order to check them and finally discovered that B04-10 was slightly cracked (it is the one at the bottom-left corner of the board, you could figure it was heavily bended there) and, with no surprise, it couldn’t be read on my programmer. See the crack in the middle of the chip, it was unnoticeable before removal:

Fortunately, PALs for this game are available on JAMMArcade.net so I took a blank GAL and burned the equivalent file but then got a black screen… Ok, that was my fault as the file was an untested dump from a PAL16L8 and needed to be converted to GAL16V8 in order to work properly. I did the conversion with PALTOGAL.EXE, reburned it then the game booted !

Great… But my enthusiasm quickly stopped as I noticed some issues:

1) The game sometimes crashed then rebooted, it happened 1/3 times when I started a game.

2) There was no sound (I could sometimes randomly hear a voice looping then fading away).

3) A few sprites were garbled.

It turned out that both issues 1) and 2) were related to a defective sound RAM chip @ IC50.

System11 reports the exact same problem on one of his Rastan repair logs (corrupted sound with main CPU crashing randomly due to a defective sound RAM).

This was not easy to troubleshoot because that RAM @ IC50 had seemingly “normal” pulsing signals on every pins and piggybacking didn’t worked at first. After reading that repair log from System11, I tried again piggybacking and that time it worked ! (well, it partially worked and not all the time)
So I’ve replaced the chip and got it working fine with sound and no freezes !

Only the issue 3) was remaining. The fault was most probably due to one of the gfx mask ROMs @ IC28 (1Mbit into a 28pins chip) that was replaced by an hacked 27C010 1Mbit 32pins EPROM. I could see things changing when touching a couple of pins on the EPROM. Here is a picture of it:

I could replace this bad looking hacked EPROM with a blank TC531000, LH531000 or a HN62331 mask ROM as they seems to have the exact same specs and size than the original mask ROM but it seems nearly impossible to find these chips nowadays.

After comparing the pinouts between 1Mbit 32pins EPROM and 1Mbit 28pins MASK ROM I found what was missing on that hack: pin #2 (A16) of the EPROM was not going anywhere and it should be connected to pin #22 on the socket. I soldered a thin wire on the EPROM and plugged it underneath the chip on the socket.

Plugged back the chip and the gfx were then fully fixed ! (as an example, this axe on the bottom-right corner was garbled before):

Alright, BUT… After playing the game for a few minutes, I noticed when dying that Rastan’s voice was suddenly cut and looped 3 times along with his jumping voice. If I had to replace what I heard with words that would make: DYING/cut/JUMPING/DYING/cut/JUMPING/DYING/cut.
Well, that sounded weird so a verification in the emulator confirmed that was not normal.

The test mode features a sound test so I compared all the voices between my board and the game in MAME and there was 3 voices replaced by this looping sound of Rastan’s dying/jumping.

Alright, had to look back at the schematics…

This was (most probably) related to the voice generating part which is pretty small fortunately as it involves only a few TTLs as well as the Z80, one EPROM and one M5205 (ADPCM sound generator).
Sound ROMs were tested OK and every address and data lines looked fine.

Checking the related TTLs with the scope, I noticed there was no pulsing signals on every of the 5 outputs of the 74LS193 @ IC60 while its inputs were pulsing. This chip is a counter and it is partially doing the link between the sound data bus and the voice address bus. There is another 74LS193 @ IC77 doing the same work for other address/data lines and outputs were pulsing when I pushed the button to generate one of Rastan’s voice in the sound test.

Piggybacking the chip at IC60 made the voices working fine with no weird loop. Also the other voices in the sound test were back. Replaced the chip and finally have now a perfectly working Rastan. (well, played it a few hours and it runs perfectly !)

Thanks to Porchy and Caius for their help on the PAL and hacked EPROM.

Super Contra repair log #2

PCB Repair Logs, Repair Logs 2 Responses »

Aug 292015

A friend asked me if I could take a look at his dead Super Contra PCB which was a 2 boards version (the same game exist in a single board version where all the small mask ROMs on the sub board are replaced by bigger mask ROMs on the main board).

All I got was a black screen with no sound. Checking with a scope around the CPU area revealed there was almost no activity. The CPU is a Konami custom 052001, hard to troubleshoot as I couldn’t find its pinout online.

While checking for possible loose connections on some chips. I found that bending a bit this small chip near the JAMMA connector (an electromagnetic interference filter) was booting the game:

It was a bit loose. I desoldered it and found one of its legs broken. This was hidden behind one of these two small black ferrites. I repaired the leg and resoldered it.

Well, the game was now booting but graphics were a bit messy:

scontra4

ROMs containing graphics and voices are located on the sub board.

I started checking this part as it has a pretty simple layout (basically mask ROMs with buffers) and noticed 3 mask ROMs with corrupted signals on their data lines. These 3 ROMs were all connected on the same bus to pins 2 to 9 (A bus) of a 74LS245 buffer @ location D1:

There are several other 74LS245 chips connected to other mask ROMs on the board and they all seemed to have “normal” activity signals. The B bus of the suspected chip (pins 11 to 18) seemed inactive and was connected to a custom chip on the main board.

I first tried piggybacking that 74LS245 @ D1 but nothing happened. The lines were still looking the same with garbage signal on bus A side, which could be caused by the possibly faulty chip itself. I desoldered it and it was tested bad on my IC programmer. I put a new one in place and the problem was resolved:

Here is what every signal on the A bus (pins 2 to 9) of the 74LS245 chip looked like with the faulty chip (left) then with a new chip in place (right). You can clearly see how bad the signal looked like on the left:

Pang repair log #2

PCB Repair Logs, Repair Logs Comments Off

Jun 162015

Got a friends Pang PCB here for repair.
He had carried out the ROM swap (made by ArcadeHacker) to desuicide it but he had no output although we could hear it playing blind.
The board is very clean and a visual check revealed nothing.
On powering the board up I got this screen

I could also hear the board did play blind so that’s a good sign.
I like to make little schematics for boards when I’m working on them and they don’t have any available and I quickly came up with this.

I started probing back from the RED pin on the JAMMA edge connector and soon came to a RAM chip at location 8C. Probing this chip and its counterpart gave me some odd looking signals which I got suspicious about.
These chips are CXK5814 SRAM chips and they seem the be the most unreliable RAM by comparison.
One of the RAM’s had all its data lines stuck LOW while the other chips data lines were all dead despite all the enable lines working as they should and the address lines active.
At this point I was certain they were dead but one last test was to ‘piggyback’ a known good RAM chip on top of the suspected bad one. I chose the one with the dead data lines to avoid potential contention and I got a partial image on screen.

I desoldered both the RAM chips and replaced them. I didnt have any spares in my RAM bin but found a couple of skinny 6116 RAM’s on a scrap bootleg board.

Fitting these I now got this wonderful sight.

Job done.

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