Had this bootleg of R-Type (manufactured by Philko) laying around since some time:

On power up board was stuck on this garbage static screen:

Like in the original Irem hardware main CPU is a NEC uPD70116 (a.k.a. V30)

Probing it revealed that the RESET signal (active HIGH on this CPU) was missing, pin 21 was going  LOW on boot with no transition from HIGH state hence no initialization of the CPU itself

But if I manually resetted the CPU by briefly shorting pin 21 to +5V via a 100 Ohm resistor, the board successfully booted and played perfectly:

Traced pin 21 of the CPU back to pin 10 of the uPD71011 whose pin 11 receives the RESET signal and invert it  :

Also the /RESIN input had no initial transition so the problem was upstream.Compared to original hardware the bootlegers semplified the power-ON delay circuit purposely omitting the M51202 voltage comparator (although  there is silkscreening and room for it).They used insted few discrete components like a diode, a resistor and an electrolityc capacitor which actually was not present @C6 (most likely it went detached)

This was the cause of the missing RESET.I fitted a 100uF 16V electrolytic capacitor (after experimented different values) and board booted all the time.Job done.

Received this original Ninja Emaki PCB (manufactured by Nichibutsu) for repair:

Board gave a solid black screen.After a quick visual inspection, I noticed one IC was missing from its socket @1B on CPU board:

My searches confirmed the missing IC was actually a PAL but sadly I had no access to other same PCB in order to read or reverse the device.Here bootlegs come handy since often they are perfect reproduction of the original hardware and, judging from pictures I found online, this was my case :

I quicky managed to find a Ninja Emaki bootleg and one received it I realized that the missing IC was a PAL16R4 so a secured registered PLD hence not readable or reproducible :

My only choice was  to take this chip from the bootleg and install it on the original board.I made it and board sprang to life:

 

Game was playable but background were scrambled as you can see from above picture.I noticed that if I pressed or flexed the board in some points, the graphics came back in place.A closer inspection revealed some dry joints on solderside of an EPROM:

Reflowing them fixed the board completely.

Got this X-Men PCB for a repair :

As often happens on Konami boards that use hybrid audio module (the ‘054544’ in this case) audio was horribly scratchy and loud:

Electrolytic capacitors  had already been replaced with same type but this obviously was not enough:

So, I removed the module from PCB and decided to fully service it:

I replaced with new parts the 4558 OP-AMP (I used a compatible LM358) and the AD1868 DAC as well:

At same time I reinforced some poor connections  :

Lastly, as icing on the cake, I varnished with black laquer :

As always I do, I installed on PCB a couple of 1.778mm female round machine-tooled strips.This was the final result:

Time to test :

Job done.

P.S.

For the uninitiated, the ‘054544’ module has been reproduced, you can read more about on these threads:

https://forums.arcade-museum.com/showthread.php?t=386416

https://forums.arcade-museum.com/showthread.php?t=396393