I got this Toaplan Knuckle Bash from my friend Josef for a repair.
He said board showed graphical issue which he could clear only by raising the 5V to +5.5V.After powered it up I had confirm of what he told me, actually colors were bleeding (you can notice it on right part of the picture below):
Schematics for this board were available so I could identify the part of circuit which generates the color palette:
Data from the two 6116 SRAMs are latched by two 74LS273 (actually my board mounted two 74HCT273).When I went to piggyback the one @U9, colors were restored.I desoldered the IC but it succesfully passed the test in all my programmers, also comparing it with a good one on a tracer showed no abnormality:
Probably it was not really bad but its thresholds were altered.Despite this, I socketed and replaced it:
I thought this repair was the perfect opportunity to show you how to correctly servicing the ‘infamous’ Konami ‘054986A’ custom audio module (obviously this is valid also for the ‘054544’ one).Follow this guide at your own risk.I’m not responsible for any kind of damage!
Let’s start.
I got from my friend ‘supermik’ this Mystic Warriors PCB:
Board played fine but had an orrible sound output, very loud and distorted:
Obviously the culprit was the ‘054986A’ module whose capacitors were replaced by thru-hole electrolityc ones:
But this was not enough to fix the issue.So, instead of troubleshooting the module (the 4558 OP-AMP and the AD1868R DAC undersneath were most likely bad), I opted for its complete replacement using a Premiere Soccer as donor board :
The removal of a module consists in the following steps:
Prepare the board by covering the solderside with some aluminium foil leaving exposed only the pins of the module:
Clamp an IC extractor on the sides of module:
Put the board wrapped in a cloth or pillow between your legs:
Now, with an hot air rework station do a first preheating of a couple of minutes on the exposed solderside setting the temperature at 100 Celsius degrees.Then, set the station at 250 degrees for a minute or less:
In both cases, you have to move the hot air gun back and forth without stopping otherwise you could damage the board.
After done this preheating (needed to facilitate the solder melting and avoid heat stress) you have to use an heat gun for the last pass.Personally I use a 2000Watt model and set the temp to position ‘8’:
Keep moving the gun back and forth and at same time gently pull the IC extractor:
When the solder will arrive at the melting point, the module will come out easily from its seat:
Next step is the sockets installation, use 1.78mm pitch ones (cutting a single socket in half):
My friend ‘supermik’ sent me his Flicky PCB (released by Sega on System 8 hardware) for a repair:
When I powered it up,I got this scenario:
Sprites were fine but backgrounds were all wrong.Tiles data are stored in six 2764 EPROMs devices:
When I removed them for dumping, I noticed a broken pin on one device which I promptly rebuilt:
At same time I replaced four sockets of the tiles EPROMs (similar sockets are used also on Konami boards, they are beautiful but unreliable):
Backgrounds graphics were good now but still some glitches were present:
As I said, I dumped the six tiles EPROMs and they matched the MAME ROM set.But something still didn’t convince me so I used my video probe to check where the part of graphics affected was generated.For the uninitiated, the video probe is a small device that routes the green input from JAMMA to the video output allowing you to see on your monitor the signal captured with a probe.You can read more about here:
PCB Repair LogsComments Off on Raiga – Strato Fighter repair log
Sep302015
I got on the bench this Raiga – Strato Fighter PCB for a repair:
Game is a horizontal side-scrolling space shooter developed by Tecmo in 1991.Two were the issues I got when I powered it up.Sound was completely missing ( I got only some samples played randomly) and there were missing vertical lines all over the screen like a sort of scanlines effect:
All video related circuitry is located on he bottom board.Since involved EPROMs and RAMs were socketed I could test them out-of-circuit and they were fine.Then I noticed some dynamic RAMs in form of 12 Sharp LH2464 (64K*4bit) chips.I went to probe them with my oscilloscope and I found weak signals on two data lines of a couple of them (good signal on left, bad on right of the below picture):
So, I removed the two chip and tested into my EPROM programmer where they both failed:
With two good DRAMs fitted, the graphics were completely restored:
So I went to troubleshoot the lack of sound.Main CPU of the audio digital section is a Z80 which commands two YM2203 FM sound synthesis chips for the music and one OKI 6295 for the voice samples.Probing the Z80 revealed random activity/pulsing on all its pins.Besides, chip was wery hot to the touch so I decided to replace it.This was the right move.Board 100% fixed.
PCB Repair LogsComments Off on Jigoku Meguri (Bonze Adventure) repair log #2
Sep282015
My friend ‘robotype’ sent me some boards for a repair.I hope this log will the first of a long row! 🙂
Let’s start with this Jigoku Meguri (the Japanese version of Bonze Adventure) :
all
Board played fine but was silent, no audio at all.Digital part of circuit was fine, Z80 CPU was active and healthy so the fault had to be in the analog section.Main amplifer was good producing some noise when I put my fingers on its pins.Other component involved in analog section were a YM3016 DAC , a couple of TL074 and a uPC4556 OP-AMPs:
As usual I went to probe the analog output (pin 13) of the YM3016 DAC and sound was present although scratchy and distorted:
So I decided to replaced this DAC :
In this way the sound from it was fine:
but board was obviously still silent.Following the path of the signal I came to the near uPC4556 OP-AMP.Sound was still present on its inputs not nothing came out from outputs.I replaced it with a compatible LM358 and this restored sound.End of job.
