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.

Antoher board from the same batch of Sega System18 motherboards.

Ths is the time of a Taito F3 game (PCB version), Arabian Magic to be precise.Hardware is quite powerful as you can see from specifications:

• CPU: Motorola MC68EC020;
• Sound CPU: Motorola MC68000;
• Sound chip: Ensoniq ES5505 and ES5510 (DSP);
• Video resolution: 320×224;
• Board composition: Board and F3 cartridge;
• Hardware features: four scrolling layers, two sprite banks, Alpha blending

Board was in good condition :

It worked fine except for two stuck intupts (P1 and P2 2nd button) as you can see from I/O TEST mode:

In this kind of hardware all I/O (and watchdog, too) are handled by a custom ASIC marked TCO640FIO (120 PIN QFP package) @IC71:

All the inputs from JAMMA connector are connected first to pull-up resistor arrays so I checked them and they were good.Lastly I lifted involved PINs from ASIC but inputs were always stuck.So, at this point, replacing the ASIC, taking it from a donor board, was my last resort.So, time to remove and replace it:

and…success!All the inputs were restored and game fully enjoyable!