Caius

May 252018
 

I’ve been sent from Germany some faulty PCBs for repair.There were among them two PCBs manufactured by Toaplan :

  • Knuckle Bash

 

  • Fixeight:

The first was throwing a “A VRAM ERR” message on boot:

The video RAMs (VRAM stands for this) are two 8k x 8-bit static RAM located @42 and U51:

They are accessed by the QFP ASIC marked ‘GP9001’ which is the graphics controller of the system:

For first I did a visual inspection of it and found some pins not really firm (common issue on QFP with this fine pitch)

I reflowed them but this didn’t led to any improvement so I moved to check the VIDEO RAM ICs and found weak signal on data lines:

I pulled both RAMs, only the one @U42 failed the out-of-circuit testing:

The board successfully booted into game now but the colors were wrong, they were “bleeding”:

This is another common issue on this board so I knew where to look exactly.The data bits from the two 6116 (2K x 8-bit) palette SRAMs are latched by two 74HC273:

Probing with a scope the 74HC273 @U9 revealed weak signal on outputs (inputs on the left of the below snapshot, outputs on the right)

I pulled the IC:

It actually passed the out-of-circuit testing on all my programmers so I think IC was not really bad but it had altered voltage thresholds.Anyway, I replaced it and this fixed the board completely.

 

 

Now the FixEight troubleshooting.

Board gave me a steady black screen.This board uses the GP9001 graphic controller too:

Found some lifted pins on it:

I reflowed them as well as replaced the main program code 4Mbit EPROM since it had some rebuilt pins that gave me trouble when dumping it:

But still no boot.But I noticed that pressing  the PAL16V8 @U51 :

produced a couple of different RAM error messages on screen:

Solderside of the PAL socket had some dry joints:

So I replaced it and finally the board initialized but it quickly went straight into SERVICE mode and then reset in an endless loop :

 

From a still image I noticed that some inputs were stuck in I/O check:

The inputs are handled by the custom ‘HK-1000’, you can find more info about it in a past article from mine:

Toaplan ‘HK-1000’ reproduction

On my PCB a replacement board had been used in place of the original part:

Some inputs of a 74LS240 on this replacement board were shorted to ground.Instead of repairing it, I opted for a reproduction of mine (the blue jumper wire was already there to patch a trace previoulsy broken during the removal of the original ‘HK-1000’)

Finally the board booted into game with no further issues.Toplan double repair log accomplished.

 Posted by at 9:24 pm
May 242018
 

Received from USA this Psycho Soldier PCB:

It was labeled as ‘DEAD’:

And it was so, all I got was a steady black screen but this was not a suprise to me since the boardset (a three stack one) was fully populated by Fujitsu TTLs.First thing I checked was the presence of clock on CPUs, it was missing on both main and sub Z80 (but present on sound one)

I traced the signal from CPU board back to a 74LS367 @10A on bottom board:

Input pin 6 was properly receiving the 16MHz clock from the nearby oscillator but output pin 7 was floating:

As expected the TTL obviously failed the out-of-circuit testing:

Board sprang to life but colors were mostly incorrect and also sprites wrong and garbled during moviments :

I focused my troubleshooting on the bottom board as it contains sprites and background data and circuitry :

For first I checked the EPROMs, some of them were oxidized and corroded:

Afer some cleaning I dumped them, they were all good.So I fired up my logic comparator to test TTLs in circuit and found a couple of them with floating outputs (that’s the way Fujitsu TTLs are used to fail)

This restored the correct sprites :

But colors were still wrong.This was confirmed also in SERVICE mode, none of the them were correctly displayed:

The RGB lookup tables are stored in three 1k x 4-bit bipolar PROMs (Fujitsu MB7122 used here)

Probing the devices revealed that two address line were stuck high, I traced them back to a nearby 74LS174 @1M whose inputs were missing.These came from the outputs of a 75LS153 @1P-The TTL didn’t look very good with rust and corrosion on its pins:

The scope confirmed that both outputs had no valid voltage logic levels:

I pulled it:

Obviously it failed the out-of-circuit testing:

Colors were finally good and game played fine but I noticed there were some horizontal lines on left of the screen during scolling (see from seconds 25 of the below video)

At first glance I thought it was a fault but then I’ve been told by the owner and my friend Corrado that it’s actually a bug of the PCB.MAME Testers site confirmed it too:

http://mametesters.org/view.php?id=2910

I was about to close this repair when during testing suddenly the board failed again.Colors went bad again and lastly most of graphics disappeared:

The affected area was again the colors circuitry.The 74LS174 @1M which was previously tested as good showed floating outputs :

It failed when tested out-of-circuit:

At this point I took the chance to replace all other Fujitsu TTLs in this area :

Some passed the out-of-circuit test but two 74LS153 failed miserably:

Hard work always pays off and finally I could restore this board in all its glory (game was the first to use a fully digitized, full-length vocal sountrack)

 Posted by at 8:58 pm
May 172018
 

We have new PAL dumps from the following PCBs:

 

  • Darius II (dual screen)

‘coolmod’ sent in dumps from two PAL20L8.Board is faulty so we are unable test GAL replacements but we assume dumps are good since devices were unsecured.Thanks to him.

 

  • Power Spikes (bootleg)

I dumped a secured GAL20V8 and successfully reversed its equations onto a GAL22V10.

 Posted by at 10:49 pm
May 152018
 

The Konami ‘056820’ is a custom IC in SIL package (13 pin with an unusual 2mm of pitch) used on GX System  hardware:

Sometimes it’s wrongly reported to be an RGB DAC but if you look at his pinout (from Lethal Enforcers II schematics) you can understand it has a different function although always related to colors generation :

Its particular feature is that it gets extremely hot and may fail as a result.Here’s a picture taken from the net where the coating literally melted due excessive hot:

Driven by a curiosity I decided to take a look inside:

The biggest component in the upper left corner of the above picture is a Toshiba TA78M05F fixed voltage regulator, datasheet here:

http://www.jammarcade.net/files/Datasheets/TA78M05F.pdf.PDF

It provides on its output the +5V (regulating from +12V) to nearby custom ‘056766’which is actually the DAC  (specifically it powers the analog section of it since digital one takes the +5V from JAMMA connector).This explains why the part gets burning hot since the radiating surface of the heatsink (actually the copper of the PCB) is too small and not adequate in my opinion.All other parts are SOT-23 PNP transitors for amplify the RGB channels,   capacitors (for decoupling and voltage regulator stability) and printed film resistors, in particular there are thre 75Ohm ones to bring the RGB signals to the standard impedance level.The custom was pretty easy to reproduce, the only precaution I took in design was to enlarge the heatsink surface on the footptint of the voltage regulator.I used an MC78M05 in DPAK package since the original part is nowadays obsolete :

http://www.jammarcade.net/files/Datasheets/MC78M00_series.PDF

This granted me a better heat dissipation.Here’s the assembled reproduction :

Testing on a Winning Spike:

See you to my next reproduction project!

 Posted by at 2:48 pm
May 122018
 

The Konami ‘054573’ is a custom chip found on various PCBs from this manufacturer : Bucky O’ Hare, Metamorphic Force, Gaiapolis, Xexex, Mystic Warriors, Wild West C.O.W. Boys of Moo Mesa to name some.Technically speaking it’s a RGB DAC (one for each color) which converts into analog the palette data bits received from the the custom ASIC ‘054338’. There are no schematics showing it but it should be a 9-bit DAC .

It comes in the usual SIL package (15 pin) covered by black coating like many custom with similar functions :

I have partially covered this topic in a past repair from mine, where you can see also picture of its circuitry inside :

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

Being a important and not long reliable part I decided it was time to think of a replacement.No particular difficulties were encountered in identifying the internal parts, tracing connections and developing a PCB  which arrived from my manufacturer after some time.Here’s the reproduction finally assembled and installed :

Testing on a Moo Mesa PCB was successful:

See you to my next reproduction project!

 Posted by at 7:10 pm