Jul 242018
 

Received from Portugal a couple of faulty The Simpsons PCBs.The first one:

When powered the board up I experieced sprites issue, some parts were missing:

The MASK ROMs test reported three bad 8Mbit devices which store sprites data :

This was almost unlikely so further investigation was needed.All the sprites generation is accomplished by two ASICs : the ‘053246’ which generates addresses to the MASK ROMs and the ‘053247’ which reads their data.But, unlike other Konami PCBs with similar design, the data lines of the MASK ROMs are not directly tied to the ‘053247’ but some 74LS373 octal d-type latches are in the middle (two of them receive the whole 16-bits of each MASK ROM)

I opted for a ‘shotgun method and replaced all of them.The MASK ROMs check no longer complained and reported all devices as good:

Board completely fixed:

 

 

The second PCB:

The board was failing the POST reporting two bad devices @6G and 7G:

They are respectively the ROM and the RAM of the Z80 audio CPU circuit .

The 1Mbit ROM was socketed so I pulled it and found that one leg was missing:

I rebuilt the leg and dumped it in my programmer but I got inconsistent readings so I replaced the device.In this way the board booted into game but graphics were wrong.The sprites were missing as well as the backgrounds incomplete and with bad colors:

I ruled out the MASK ROMs by performing a check :

At this point there was not much to test, graphics generation is entirely accomplished by custom ASICs.There is one especially whose functions could be related to the issue :

The ‘053251’ is a priority encoder which takes on input different layers of graphics as well as some priority bits and outputs 11 bit of palette index plus two shadow bits (info taken from MAME source)

Probing the output pins with a scope revealed weak signals on most of them:

I removed the IC preparing then the area to accomodate the spare part:

I took it from a donor Premiere Soccer board:

This restored graphics.Board fully working again.

 Posted by at 9:08 pm
Jul 222018
 

I’ve been sent from Portugal a box of faulty PCBs for repair with some Toaplan stuff inside like Vimana and Out Zone (both japanese revision)

Vimana :

Board was booting and played fine except for some little glitches on background:

Backgrounds data are stored in four 28 pin 1Mbit MASK ROMs:

Devices were dumped fine except the one @ROM3 which gave inconsistent readings.Loading the file into MAME emulator reproduced the issue exactly:

I replaced the faulty MASK rom with a 32 pin 1Mbit non-JEDEC EPROM (adding the missing sockets)

Board 100% fixed:

 

Out Zone :

Board booted but sprites were garbled :

Probing a row of RAMs revealed /CE pins on three of them  (the two 6264 @13A-14A and the 6116 @16A) were receiving no signals :

At a closer inspection I found a burnt trace going under them:

I removed two of the three involved RAMs:

Tracing back the burnt trace I figured out it was a GROUND signal that should have been daisy-chained to the /CE lines (grounding also address lines A10-A9-A8 of the 6116)  of the three RAMs enabling the chips.A couple of jumper wires did the job:

 

 Posted by at 10:24 am
Jul 202018
 

The ‘Konami 054574’ can be found on some PCBs from this japanese manufacturer always along with the three RGB DACs ‘054573’ (see past article for this ) so this reproduction is the natural follow up.

It shares the same SIL package and pin counting :

As well as most of the internal circuitry with open collector buffers, R/2R and transistors:

Its functions are not really clear though, for sure it’s connected to the above mentioned ‘054573’ and the ‘054338’ (which is a color mixer for special effects) so possibly it’s a RGB mixer/filter.

I simply reproduced it at ‘low-level’ identifying all the parts with their values and figured out the circuit schematics.Here’s the result .

Testing was successfully carried out on a Wild West C.O.W.Boys of Moo Mesa PCB :

 Posted by at 8:51 pm

Konami ‘007593’ & ‘007327’ reproduction

 Reproductions  Comments Off on Konami ‘007593’ & ‘007327’ reproduction
Jul 142018
 

The ‘007593’ and ‘007327’ are two custom ICs found on many PCBs manufactured by Konami in end 80s.This should be a complete list:

‘007593’ on :

  • Black Panther
  • Contra / Gryzor
  • Hyper Crash
  • Salamander/Life Force
  • City Bomber
  • Kitten Kaboodle / Nyan Nyan Panic
  • Labyrinth Runner/Trick Trap
  • Vulcan Venture / Gradius 2

‘007327’ on :

  • Combat School /Boot Camp
  • Rock ‘n Rage
  • Jackal/Top Gunner
  • Flak Attack
  • Devil World / Dark Adventure
  • Double Dribble
  • Rack ‘Em Up/The Hustler
  • Haunted Castle
  • Super Contra
  • Battlantis
  • Blades of Steel
  • Ajax

Both ICs have strong similarities starting with how they appear:

Analogous package apart, they have same function as we can see from schematics:

But the ‘007593’ and ‘007327’ are not simple RGB DAC as  you can think of at first glance but they embed a complete palette color circuitry on a single chip.So not only RAMs but, as you can see, many other ICs in form of bare dies covered by coating as well passive parts :

Therefore, for this reproduction project I used a different approach.I studied previous Konami hardware figuring out how the color palette circuit was engineered without the use of the customs.After drawed my schematics I reproduced the ‘007593’ for first:

Once successful tested,  it was the turn of the similar ‘007327’ :

Testing on their respective boards:

The layout of both reproductions could be surely optimized (with consequent reduction of the size of the board) using moderm complex programmable logics but I’m happy enough with them since my primary goal was to study a working replacement for these two custom ICs which seems quite prone to failure making our beloved PCBs unusable.

 Posted by at 12:11 pm
Jul 132018
 

Recently I decided to take a look at another custom IC, the Taito ‘PC030CM’:

It’s a 20 pin chip in a brown-ish SIL package used on some PCBs like Arkanoid, Bubble Bobble, Big Event Golf and few other.Like schematics shows, the ‘PC030CM’ handles coin inputs as well counters/lockouts:

If the part fails (most of times it breaks due its fragile nature), the board will no longer boot, an ‘I.O ERROR.’ is all you will get:

For this reproduction project I had no need to inspect or analyze the part but I simply re-engineered,using SMT devices, a replacement board that can be found on some Arkanoid bootlegs:

Then I compared my schematics to work previously done by ‘JROK’ on KLOV forums and, once verified everything, I  designed a proper PCB.Here’s the reproduction how looks fully assembled (I ordered it with red soldermask but manufacturer wrongly made it blue)

For the testing the user ‘manimani’ on Neo-Arcadia forum kindly sold me an original Arkanoid PCB :

The board was missing the ‘PC030CM’ custom :

Some workaround was made in such a way that the board could coin up the same using the SERVICE button instead :

So, this was a perfect platform test for my reproduction which worked fine:

Thanks again to ‘manimani’ and ‘JROK’.See you at my next reproduction project.

 Posted by at 10:07 am