PCB Repair Logs – Page 87

Pretty Soldier Sailor Moon repair log

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)

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

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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.

Robocop 2 repair log

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Jun 242015

The game was working fine but you could hear only the sound fx, not the music.

Usually these kind of issues are related to either the DAC or the operational amplifier connected to the FM sound chip.

I used my external amplifier to probe the output of an operation amplifier and I could hear perfectly the music.

After checking for interrupted lines I noticed a missing cap.

Bridging the two pins restored the music.

Easy job!

Kyohkoh-Toppa (BreakThru) repair log

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Jun 232015

Maybe the name “Kyohkoh-Toppa” doesn’t say anything to most of arcade collectors/fans but if ,instead,I said “BreakThru” many of you will remember a game whose goal is to drive a dune buggy to “breakthru” the enemy lines of five different areas.So, for those who still have not understood, “Kyohkoh-Toppa” is the japanese version of BreakThru released by Data East in February 1986 for the eastern market.

Here is the PCB:

Board booted fine but it had a graphic issue since sprites were missing some lines:

I noticed that problem went away if I flexed the board so there was some poor contact somewhere.In this kind of hardware all the graphics is generated in the bottom board so I reached it and found this:

Someone (certainly not manufacturer) replaced two TMM2018 300-MIL SRAMs with two 600-MIL equivalent ones adapting them in narrow sockets!For a better understanding of the package dimensions:

Not a neat job, for sure…Anyway, I could pinpoint sprites issue in the SRAM @11E (the one of the left picture) since problem was cleared when I pressed it.As you can see from picture they used some jumper wires on part side while patched some broken tracks on solder side :

So, I decided to remove this hack, check that all the RAM connections were fine and use a proper 300-MIL chip in a new socket :

In this way sprites were stably restored and board 100% fixed.

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