Got K1ngarth3r’s Mega-Tech PCB here.

On these boards there is a daughterboard present which houses the Z80 used for the menu.

This daughterboard is used for book keeping and isn’t really required so to save space I fitted the Z80 directly into the slot the daughterboard previously occupied.

The fault was the board didn’t see slots 4, 6 or 7 as shown in the picture he sent

Initial inspection showed the EPROM for the menu was fitted upside down but it wasn’t dead and the menu wouldn’t work at all if this were the actual fault.

Using the partial schematics I made a few years ago I could quickly pinpoint an area to start checking from.

Using my latest favorite tool, Slice, I could easily see that for some reason the 3 aforementioned cartridge slots were never being addressed.

This is a bit weird as on initial look at the disassembled code it seemed that it just counted through the slots.
A bit more code scrutinizing revealed that the CXD1095 chips are read back between slot addressing.
Using the Fluke 9010 I could now see that at certain output configuration on the CXD1095’s would lock up the chip and skip whatever it was doing.
I wasn’t really surprised at this because every single Mega-Tech PCB I’ve looked at has had issues with these chips.
I ordered a couple of these chips up and waited….. and waited……… and waited until I got hit with a lovely little letter from Royal Mail telling me I owed them money for customs fee’s.
I paid this and a couple of days later I received my items.
I removed the old and fitted the new

Pleased to say this board is now working again

Got this board from Olly.

Board looks very clean and plays but has graphical issues

Initial visual inspection showed nothing. All voltages seemed fine too.
Next I started gently pressing down on the custom chips which made a lot of changes when I pressed on 053250

Found a bunch of pins on that were lifted.
I reflowed these and checked the rest of the chip which all seemed fine.
Next boot up test gave me a lot better results but there were jailbars down the whole screen sometimes.

Continuing pressing the custom chips I could make everything change again by pressing on custom 054157.

Found most of this row lifted

and few a few here

Reflowed those little guys and all is fixed in Xexex land.
Its a really nice game that I’ve never played before.

Got for repair this original Rapid Hero PCB, an obscure vertical shoot ’em up released by NMK in 1994 and a very sought-after board :

The board booted up but some sprites were affected by jailbars :

Besides, an entire music track was missing or sometimes corrupted as well as some sound effects:

 

The board had some sign of previous repair on solder side :

This is the area of the ‘CN1’ and ‘CN2’ connectors where the ROM board, which contains all the game code and data, plugs into the mainboard:

The repairs let assume a weakness and subsequent failure of the headers connections probably due to repeated disconnections and insertions of the ROM board.So I checked with a multimeter in continuity mode all the traces from the ‘CN1’ header and found another broken one that I promptly patched :

This fixed the graphics, no more jailbars on sprites :

Now the sound issue.

The audio circuit was previousy reworked, one of the OKI MSM6295 was likely replaced and one trace was repaired but this was not the culprit :

I noticed that if I pressed the ROM board on the ‘CN2’ connector some of the missing sounds were restored.I checked traces from ‘CN2’ to mainboard and found two missing connections to the ‘NMK112’ custom ASIC (responsible of  bankswitching the sample ROMs of the two OKI6295 ADPCM chips)

I patched the traces with some AWG30 wire:

Sound was totally restored and board 100% fixed.Repair accomplished.