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.

 

 

Some days ago a friend of mine sent me some faulty boards to be repaired.Among them there was a couple of Sega System18 motherboards which, according to him, were working fine except for audio issues.You may think these kind of faults are easy to fix but instead most of times they requires accurate and long troubleshooting since audio circuitry is made of a digital and analog part (the latter has a lot of passive components like diodes, resistors, capacitors, OP-AMPs and so on)

So I started my analysis with these optimistic assumptions.

The first motherboard (which, actually,  belonged to a Laser Ghost boardset) came without CPU and ROM board :

so I used the ones from a my Shadow Dancer boardset.When I power it up I could hear sound but it was disorted and missing some PCM samples.First thing I replaced both TL084 OP-AMPs and this improved  a little the quality of sound but not still perfect and sample were always missing.These ones are played by the ‘RF5C68A’ PCM chip manifactured by Ricoh:

https://en.wikipedia.org/wiki/Ricoh_RF5c68

Connecting its analog outputs to an external amplifier I could hear all the missing samples but then they were lost somewhere since they didn’t come to the OP-AMP inputs.So, time to investigate deeper.With my ESR meter I started to check capacitors in the analog section and I found  some electrolytic ones (three 100uF 16V @C32-C36-C44  and one 220uF 16V @C35, all of same manifacturer) with very high ESR:

Once replaced them sound was clear and all PCM samples present again.

 

Let’s pass to the second boardset which came complete with its Desert Breaker ROM board :

In this case music + sound FXs were all present but very noisy.For first I checked the two TL084 OP-AMPs (actually two NEC uPC804C ) with my oscilloscope and all outputs were fine except for a couple  of both operational @IC92 and IC93 which showed clear disturbs (measured in AC) compared with respective good inputs:

Replacing them both with equivalent parts fixed all the sound issues.