Another board from the recent operator raid, an original Michael Jackson’s MoonWalker (on Sega System 18 hardware)
Despite its age and the use of the FD1094 CPU module with battery backed-up RAM the board was still working except for the sound samples (drums, speeches, etc..), they were missing or replaced by random ones:
The hardware uses a rebranded Ricoh RF5C68 as PCM sound chip :
Not able to find any datasheet I went to “listen” its pins with an audio probe.When I hit the analog outputs (the IC has an on-board DAC) I realized that sound came already wrong out of it.So the chip was the only responsible and it needed to be replaced:
Picked-up this Asterix PCB in a recent operatot raid:
Board was physically damaged, one part of PCB was litterally missing and the nearby 16Mbit MASK ROM was cracked in half:
The affected part was not a vital section of circuit (but only a spare room for not used additional MASK ROMs) so board still booted but sprites were missing.If I pressed the ‘053245’ ASIC they came back but garbled and blocky:
For first I reflowed some bent pins of the ‘053245’ sprites generator:
Then I replaced the broken 18Mbit MAS ROM @3K with a compatible 27C160 :
This improved things but not still perfect :
The MASK ROMs check complained about the other device containing sprites data (the one @7K)
Like said in my previous Parodius DA! repar log, this doesn’t necessarily imply that IC is faulty but also that it cannot be reached by the device which wants to read/write it.Address bus is shared among the two MASK ROMs @3K and 7K, doing a check with my muktimeter all was fine except for pin 42 of both, I got no continuity between them :
Pin 42 is the higher address line:
I simply ran a jumper wire, this restored sprites and fixed completely the board:
Received this faulty Parodius DA! PCB for a repair:
The fault concerned the graphics, there were jailbars all over the screen :
Clearly the tilemap generation circuitry was involved, this is made of two 4Mbit MASK ROMs and two ASICs that work in parallel : the ‘052019’ generates the address lines and the ‘051962’ receives the data from the MASK ROMs and process them :
The MASK ROMs check reported the two devices @K13 and K19 (containin tiles data) as bad:
The MASK ROMs @K19 was already removed and socketed.I dumped the device and my programmer warned about a poor contact of pin 13 (data line D0)
Replacing it with a 27C400 produced very little improvements, the test still reported the two bad MASK ROMs.This meant the main CPU could not reach the two devices (thru the ‘052019’ ASIC) so I went to do a continuity check.All the address lines should be daisy-chained between the two 4Mbit MASK ROM and the ASIC but I found some broken/bad contacts from the one @K19, whoever replaced the device managed to break some connections.Here the solderside overview:
Here are some close-up (taken with a microscope) of the invoved pins (pin 1-5-13)
I restored the connections but still got jailbars:
Chcking the data bus of the tiles MASK ROMs I found a bad via which should have tied pin 29 (data line D19) 0f the device @K19 to the near ‘051962’ ASIC (which processes the tilemap data)
Patching it restored completely the graphics.Job done.
This is a very short update which covers the replacement of the VLM5030 Speech Synthesizer chip which Konami used in various games.
Today my eBay order of 5 x VLM5030 Speech Synthesizer chips arrived in the mail. I only needed one but who knows when the other 4 will come in handy for future repairs.
Removed the old IC. It’s probably not clear from the picture but this IC got very hot at some point. The marks left aren’t as obvious as what I discovered under the 2149s at A19 and B19, I might need to look at those later.
I didn’t have any 40 pin sockets available but I was really itching to try this out so I soldered the chip in anyway.
Cycling through the sounds and playing them in diagnostic mode verified the fix for this. I also ran the game to verify this as well.