Jan 202018
 

Received from Austria this faulty Kuri Kinton PCB, an obscure fighting game manufactured by Taito in 1988 :

Board is very compact, hardware platform is called ” Taito L system” based on the the ‘TC0090LVC’ (a custom Z80), an all-in-one  CPU/system controller  which does everything  (game logic, tile handling, sprite handling, I/O handling, etc).At power up I was greeted by this scenario:

The game played almost blind, you could coin up but graphics were all scrambled.Ruled out the two GFX 4Mbit MASK ROMs, very few was left to probe.There are four 62256 SRAMs (32K x 8-bit) whose data/address busses are tied to the ‘TC0090LVC’ :

Probing them revealed unhealthy signals on data lines of some of them:

I decided to remove them all :

Actually only the ones @IC and IC10 failed the out-of-circuit testing:

Replacing them fixed board completely.End of job.

 Posted by at 6:42 pm
Jan 162018
 

Raise your hand those of you, arcade enthusiasts/colectors, who have never dealt with the Konami ‘054986A’ and ‘054544’ audio modules?I think none…

This little project needs no introduction and technical explanation, we have treated this topic many times during our repairs.I simply reproduced (be careful, not reverse-engineered!So my repro still need ICs of original, especially the ‘054321’ ASIC) my way both modules with same results of original parts.I hope this will be useful for preservation purposes of our PCBs.

 

 

 Posted by at 11:24 pm
Jan 162018
 

Received from Austria this pretty mint Xexex PCB:

According to the owner the board had only faint sound but actually it was not booting for me resetting on attract mode:

At a closer inspection I found some lifted pins of the custom ‘053250’ which I promptly reflowed :

Finally the board successfully booted but, as expected, with very low sound , you could barely hear it with volume set at maximum level though:

Obviously the culprit was the ‘054544’ hybrid audio module:

I removed it and changed all the electrolytic capacitors (repainting it as well) 

This restored full sound.Then I thought this was the right chance to try out my reproduction:

Testing was successful : 

 Posted by at 10:21 pm
Jan 082018
 

This is another little reproduction project that arose during my repairs.

Some time ago I came across an Heavy Unit PCB which played fine except for the inputs that were not working.This had an explanation:

This SIL custom (in ZIP46 package) marked ‘MC-8282’ was broken in half.Like the silkscreening tells, this custom handles all the inputs.I looked into my spares and found some Kaneko boards that used a similar custom with same number of pins but marked ‘MC-1091’ instead :

I tried it in my board and all inputs were working again so I came to the conlcusion that the ‘MC-8282’ and the ‘MC-1091’ are essentially the same.Not happy enough, I  decided to try to reproduce it.As always in this case, I first ‘stripped off’ the component by removing its coating and did some hi-res scans: 

As you can see from above picture, the designers pratically embedded in a single component a typical inputs circuit that can be found on many arcade boards.Techinically we can think of this custom like a big multiplexer made of four 74SL253 TTLs which receive on their inputs the signals from JAMMA edge connector.Obviously there is a common output enable signal and two selection ones as well.All other parts are printed film resistors (the black squares, the tiny ones are for pull-up), ceramic capacitors (for by-pass and signal filtering) and a couple of SOT-23 parts (involved in P1 and P2 coin input) which I was able to identify as dual common cathode diodes :

I fired up my multimeter in continuity check and in some time figured out the design so I made some rough prototyping on a breadboard:

I had success so I start to draw schematics.I intentionally omitted some not vital parts (like the many ceramic capacitors) and used SMD resistors arrays, this allowed me to save room on PCB layout and keep the same dimensions as the original part.I sent the design to manufacturer and received the bare PCBs after some weeks:

I assembled a unit:

and installed it on PCB:

Testing was successful, all the inputs of both players (plus SERVICE ) were correctly mapped and working:

For reference the MC-1091/MC-8282 custom can be found on these Kaneko/Taito/Toaplan PCBs (list can’t be incomplete so other additions are welcome) 

  • The Berlin Wall
  • Magical Crystals 
  • Bakuretsu Breaker 
  • Blaze On 
  • Shogun Warriors 
  • B.Rap Boys 
  • Great 1000 Miles Rally 
  • Bonk’s Adventure 
  • Blood Warrior 
  • Jackie Chan
  • DJ Boy
  • Gals Panic 1, 2, 3
  • Air Buster
  • Snow Bros
  • Heavy Unit

See you all to my next reproduction project!

 Posted by at 9:13 pm
Jan 082018
 

Received from Spain this faulty Vulcan Venture PCB (export release of Gradius II on the glorious’ Konami Twin16 hardware) 

This is what I got once powered it up:

Graphics were all corrupted, you could barely recognize the self-test procedure which failed all the time causing the reset of the whole system in an endless loop.I focused my troubleshooting on VIDEO board:

Like the CPU board, also the VIDEO one was almost fully populated with Fujitsu TTLs  but before going thru them I started to probe the various RAMs.I found one 62256 @8L with dead outputs:

This finding lead to no improvement.So I fired up my logic comparators and started to probe TTLs.Sequentially I was able to locate these faulty ones, all of them on VIDEO board and from Fuitsu:

  • 74LS153 @9H

 

  • 74LS157 @2F

 

  • 74LS244 @5W

But the board was still not booting :

Shorting some data/address lines of two 6264 SRAMs @3A and 3B changed the garbage on screen so this was the path to follow, the problem was in the tilemap generation circuit which these RAMs are part of :

Probing the RAMs revealed that the R/W lines (pin 27) of both were stuck high, according to schematics these signals come from a 74LS27 @4B:

 

My HP10529A logic comparator confirmed troubles on two outputs of this 74LS27 which failed when tested out-of-circuit:

Now board succesfully passed the self-test and entered in game fully playable with sound but all graphics had very noticeale jailbars:

Most of graphics data is stored in four 4Mbit MASK ROMs:

While dumping them my programmer reported troubles for the ones @10L and 10M:

 

Replaced them with two 27C400 EPROMs fixed the issue and board completely.

Evil Konami (and Fujitsu) defeated again but war is not over.See you to next battle…

 Posted by at 5:56 pm