PCB Repair Logs – Page 87

Out Zone repair log #1

Jul 102015

This repair log is proof that we must always start from the simpliest things!

Another faulty board from my friend ‘mastercello’, this time an original Toaplan Out Zone :

He told me that it worked once and then nothing.Actually when I first powered it up I got this :

The screen with the wavy lines is common on all the Toaplan PCBs which run on similar hardware.It means that the system is being intialized but it should last until the CPU starts to properly execute code.In my case this screen was permanent so there had to be a problem in the main code execution.First thing I did was to check CLOCK, /RESET and /HALT lines of 68000 main CPU, they were fine.Then I dumped the two 27C010 programs ROMs and got from my programmer a warning about a poor contact on pin 17 (which is a DATA output) of the one labeled ‘TP018_08’:

A closer inspection of the device revealed many oxidixed pins.A bit of fine sandpapering is what the EPROM device needed and enough to fix the board completely.

Donpachi repair log #1

Jul 102015

My friend ‘mastercello’ sent me this Donpachi PCB for a repair:

The board was in good shape but had a GFX issue where background layer was partially missing with lines across it:

Studying the hardware and with help of MAME I could identify the devices containing the data of the two background layers, they are two 42PIN 8 Mbit MASK ROM @U54 and U57.Probing them with a logic probe I found that the one @U54 has all its data lines stuck LOW or HIGH, also the two control lines /CE and /OE were stuck LOW though they were properly connected to a near ASIC which generates these signals.Obviously this was totally abnormal.As confirmation of my theory I was able to reproduce ths issue in MAME using a dummy ROM file of the background layer data instead of a good one:

This was enough to convince me to desolder the MASK ROM and read it in my programmer resulting in an empty dump.Direct replacement for this 8 Mbit 42PIN MASK ROM is a 27C800 EPROM though the silkscreening under the chip sais ’23C16000′:Fitted a freshly programmed device restored graphics completely.

Pretty Soldier Sailor Moon repair log

PCB Repair Logs, Repair Logs Comments Off

Jul 052015

Got this Pretty Soldier Sailor Moon PCB from my friend Ifog:

He told me that gameplay was fine but some of the audio/voice samples were missing or played wrongly.This was confirmed once I fired it up, here’s a brief audio recording:

As beginning of my troubleshooting, for first, I identified the audio digital circuitry:

As you can see from picture above, PCM samples data contained in the two MASK ROMs (40 and 42 pins) are read by two OKI MSM6295 PCM voice synthesis chips (while music is generated by a YM2151).So, I went to probe the MASK ROMs and found that the one @U47 had some address lines stuck as well as the control lines /CE and /OE.

Most of the address lines are directlty connected to the respective OKI MSM6295 chip so I replaced it but with no luck.Instead, I could trace the /CE and /OE lines back to a GAL16V8B @U28.Probing the outputs of this GAL revealed they were all stuck LOW.So. I tried to read it in my EPROM programmer which failed reporting an error:

I also read and disassembled it with my dedicated hardware, it was like empty :

/* Dedicated input pins */

pin 1 = I0; /* Unused input */
pin 2 = I1; /* Unused input */
pin 3 = I2; /* Unused input */
pin 4 = I3; /* Unused input */
pin 5 = I4; /* Unused input */
pin 6 = I5; /* Unused input */
pin 7 = I6; /* Unused input */
pin 8 = I7; /* Unused input */
pin 9 = I8; /* Unused input */
pin 11 = I9; /* Unused input */

/* Input and/or bidirectional pins */

pin 12 = B0; /* Unused input */
pin 13 = B1; /* Unused input */
pin 14 = B2; /* Unused input */
pin 15 = B3; /* Unused input */
pin 16 = B4; /* Unused input */
pin 17 = B5; /* Unused input */
pin 18 = B6; /* Unused input */
pin 19 = B7; /* Unused input */

This confirmed definitively that the device was bad.At this point the only possibility was taking a good GAL chip from another PCB or dumping and reproducing it.

Luckily my friend Ifog had a same board with a good GAL and he was able to provide me the binay dump which I took care of analysing and reversing it (see my latest PAL updates here).Once programmed a blank GAL16V8 device and fitted it on PCB, all the PCM samples were restored.Job done.

Gaiapolis & Metamorphic Force repair log (a.k.a Konami ‘054573″ color DAC reworking)

PCB Repair Logs, Repair Logs Comments Off

Jun 302015

As every arcade fan/collector probably knows, Konami makes great things but… sometimes weird.Technically speaking every their board (starting from old ones like Gyruss to latest ones ) has its own hardware layout which involves the use of custom ASICs (Application Specific Integrated Circuit).These ICs are used to semplify the layout and prevent board bootleging.They can have most disparate shape and package and do various functions (sound, graphics, I/O and so on).In particular the Konami ones are really well made but often prone to failure.Some example of their customs :

The one I faced during this double repair log is the one marked ‘054573″ .It’s used on hardware of mid ’90s, it has SIL 15PIN package and it’s essentially a color DAC, it converts digital color signal into an analog one outputting it directly on JAMMA connector (so one IC is used for each RGB colors) :

Here is the IC ‘naked” , picture kindly provided by IronGiant:

It’s a quite fragile part, indeed while I was testing a Gaiapolis PCB, I switch it OFF/ON and I got this (picture on the right) :

Green color was suddenly missing.Once identifying the ‘054573’ DAC responsible of this color I compared with a logic probe its pins to the ones of the other two DACs and they had exactly the same activity except for PIN2 which is , indeed, the output connected to PIN12 solderside of the JAMMA edge.Observed with an analog scope confirmed the output was silent compared to an healthy one of a good DAC:

Replaced it and the green color was restored :

The second PCB, a Metamorphic Force one which also use this kind of DAC, was perfectly working but someone made an awful job on the solderside, “piggybacking” a good ‘054573’ DAC on the faulty one (the green color one also here) and fixing it with hot glue:

Since the eye wants its part, I decided to revert this orrible hack restoring the original status and testing successfully the board :

Konami does great but weird things always, remember! 🙂

Ashura Blaster repair log

PCB Repair Logs, Repair Logs 1 Response »

Jun 242015

Got this pcb from ebay marked with “cracking sound problems”

The game sounded like an old LP with a lot of scratches and missed some sounds.

On this board, the YM2610 handle FM synthesis and PCM samples.

Given the fact that it is very difficult that the sound chip will fail, I started to probe the smd stereo DAC YM3016.

I could hear the same cracked sound coming out and I was sure that changing it would fix the issues.

I found a donor board and soldered a new DAC.

Retested the pcb and same problems.

At this time I was quite sure that the sound chip itself was broken.

Suddendly I remembered the most obvious thing to test first: the sound rom C43-01!

It was a maskrom….marked Taito….they had the most unreliable supplier ever.

In the past, I found many Taito maskroms which caused gfx faults because of internal faults.

After cheking the maskrom on my eprom programmer one pin was not making contact and it was clear that is was an internal break.

Burning a 4mbit eprom with maskrom pinout (like a 27c4100) restored the sound.

Older Entries Newer Entries