Found this Sunset Riders PCB in a lot bought from a former arcade operator:

The board worked fine except for the audio, sometimes wrong samples were played and often music was not present too:

The MASK ROM check reported a bad device @1D which is the one containing samples:

Obviously I removed this MASK ROM and dumped it but it turned out to be good.This device is addressed by the near ‘053260’ ASIC which processes its data as well.Tracing connections I could figured out that this custom receives serial data from the YM2151 then mixes them with PCM data and output the whole packet to the YM3012 DAC so it’s something more than a samples player, this would explain why sometimes music was missing too.Before replacing the ‘053260’ ASIC I analyzed it with a logic probe and found its pin 10 totally silent, this had to be connected to pin 16 of two 74LS245 @13F and 14F which allow 8-bit of data exchanging between the ASIC and main 68000 CPU data busses.

A simple jumper wire cured the issue.End of job.

Got this Demon’s World PCB (also known as Horror Story in Japan but game is multi-regional since it can be configured for different regions via the DIP switches) for a repair :

Board was not working, upon boot it showed the typical black/white stripes (common to all Toaplan boards) sign that main 68000 CPU has properly been initialized but then sat on a black static screen :

As said the CPU was properly running on power up but then halted before entering in game, data/address busses were both silent, usally this happens when CPU can’t find addressable devices.So I went to piggyback RAMs on board.When I did it on four 62256 @18F, 19F, 21F, 23F  :

I got this error:

I removed the four chips, most of times they resulted good when tested out-of-circuit but sometimes they randomly failed due probably weak cells.Infact when I installed new RAMs I was greeted by this screen:

Board perfectly working, no further issue found.Another repair log archived.

Sometimes it’s just matter of capacitors…We could call this repair log in this way, let’s read why.

I bought this not working  Vapor Trail – Hyper Offence Formation PCB on Ebay:

The board gave a static blank screen on power up:

Like other Data East games, hardware uses as main CPU a custom 68000 marked ’59’ :

Here you can see its pinout figured out by Porchy some time ago:

Data East ’59’ 68000 CPU Info

Probing it revealed static address/data bus, clock was present instead.Since it was not included in the above pinout I spent some time to figure out that pin 59 was the /RESET one.Probing it I found that on power up there was no transition from LOW to HIGH but pin went directly to HIGH state hence CPU didn’t get initialized.RESET circuit is a typical one made of the PST518 voltage monitor IC, a 47uF 50V electrolytic capacitor and a couple of resistors :

Checking in-circuit the ESR of this 47uF 50V capacitor @IC56 gave no reading, value was out of the 100Ohm range of my meter:

I removed it and out-of-circuit testing confirmed this capacitor was bad:

Replacing it restored a proper RESET signal so board successfully booted:

But sound was quiet despite adjusting the potentiometer and some interferences were present on screen too:

I went to measure the impedance of the electrolytic capacitors in analog sound circuit and I found many of them with out-of-specs value:

I replaced them all :

This restored a loud and a clear sound.As said in the beginning, it was only matter of capacitors!