My friend ‘robotype’ sent me some boards for repair.Among them there was this a “Kid no Hore Hore Daisakusen” PCB (キッドのホレホレ大作戦^? lit. Dig Dig Kid’s Epic Battle), a pretty obscure (for me, at least) game manifactured by Nichibutsu in the 1987 (released in the Western market as “Booby Kids”):

Board uses, surprisingly for its age, JAMMA pinout so I could power it up without the need of building an adapter as I first thought.Here is all I got, some static garbage:

This is clear sign that the CPU is not running so for first  I probed the 68000 main processor.Starting my checking from pin 1 all was stuck LOW or HIGH until I came to CLOCK (PIN15), this was completely silent.I traced it back to a typical clock circuit made of an inverter 74LS04 and a 74LS74 as divider.These ICs were good but when I went further back till to the 16MHz quartz I got this on my scope:

It was completely dead!Replacing it brought PCB to life again.

Got this mint Gundhara PCB, a vertical shooter similar to Ikari Warriors, manifactured  by Banpresto in 1995:

When I powered it up game was fully playable but tilemaps were totally wrong :

Before you start every troubleshooting, first thing to do is studying the hardware.MAME is a great help for every repairer with its invaluable source of information provided.In this case here is an overview of the hardware (thanks to driver developer Luca Elia):

• CPU : 68000 + [65C02] (only in the earlier games)
  Custom : X1-001A X1-002A (SDIP64) Sprites
  X1-001
  X1-002
  X1-003
  X1-004 (SDIP52) Inputs
  X1-005 X0-005
  X1-006 X0-006
  X1-007 (SDIP42) Video DAC
  X1-010 (QFP80) Sound: 16 Bit PCM
  X1-011 X1-012 (QFP100) Tilemaps
  X1-014 Sprites?

This information pointed me in the right direction, the part of circuit to be analysed was this:

You can see on the right part of the above picture the two custom ASIC tilemaps generator marked ‘X1-012’ (QFP100 package).When I checked the one @U45 I found some lifted pins:

A simple reflow of these pins was enough to restore tilemaps:

I was declaring this board 100% fixed but while testing it I noticed something wrong in its sound, some PCM samples were played wrongly (like enemy shots) compared to good reference of MAME.Once again our beloved emulator source gave me an help to pinpoint this trouble.There is another custom ASIC which is a 16 bit PCM chip marked ‘X1-010’ (QFP80 package) in the sound circuitry @U57:

One pin was lifted, a reflow restored correct sound.

Thanks MAME!This repair log is dedicated to you! 🙂

Another repair from the same PCB batch of previous logs (three in a row…), this is a Lethal Enforcers PCB in mint condition:

Once powered up I got this static screen:

and a ticking sound sign that board was watchdogging.In these cases first thing to check is the main CPU.Probing pins of the HD63C09E CPU (6809 compatible) I noticed that R/W (PIN32) was completely silent.This is  the control line through which CPU decide if write (active LOW) or read (HIGH) DATA onto the DATA bus.The fact that it’s an output and  it was inactive made me very suspicious.HD63C09E datasheet says that R/W line can be made in high impedance  if BA (PIN6) is HIGH but this was not my case since BA was pulsing LOW.

/WE line of 6264 WORK RAM stuck high.This is generated, indeed, by the /WR signal (PIN32) of main HD63C09E CPU through the BUS master arbitration circuitry.This lead me to desolder the CPU from board and try it in another board.It was really faulty.I socketed it too for easy maintenance:

With a good CPU fitted game obviously booted but showed jailbairs over backgorunds:

This a common problem on this Konami hardware which uses graphics custom ASICs in QFP package.Specifically Lethal Enforcers uses sprite and tilemap generators and these work always in pair.My issue was located on backgrounds so I went to inspect the pair marked 054156/054157 and found some lifted pins on the latter @S8:

I promptly reflowed them with my hot air rework station and goodbye jailbairs!Game 100% fixed.