Caius

Sep 102019
 

As someone may recall I’ve recently done a reproduction of the custom ‘CUS99’ used on Namco PCBs :

Namco ‘CUS99’ reproduction

After done it I thought it was good to take into account its “companion” too, the ‘CUS98’  which most times come along with the first.Package is pretty the same but with two further pins than ‘CUS99’

 

But functions are totally different and,  as Rolling Thunder schematics suggest,  the main one is to generate the master reset :

Secondary functions are coin counters and lockouts handling as well as lamps driving, it seems only few games (like Pac-Land and Gaplus) use this last feature :

I was obviously interested in reproducing at least the reset generation function which is essential for correct operation of the PCB  (but it seems Rolling Thunder can boot into game also with a missing ‘CUS98’).Therefore, as usual, I studied earlier Namco hardware where the custom had not yet been used and I came to a prototype developed on a breadboard:

The protoytpe worked pretty good :

Hence I developed a proper board :

Final testing on a Pac-Land PCB:

As said some functions have been intentionally omitted favoring the needed ones (watchdog circuit ad reset switch were implemented too).This will at least allow to save PCBs with a faulty/broken or missing ‘CUS98’.

 Posted by at 8:10 am
Aug 292019
 

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.

 

 

 Posted by at 10:57 am

Irem ‘KNA6032701’ reproduction

 Reproductions  Comments Off on Irem ‘KNA6032701’ reproduction
Aug 112019
 

Another custom IC successfully reproduced, it’s the Irem ‘KNA6032701’ , a 42 pin DIP 600mil IC used on M62 (Kung-Fu Master, Lode Runner, Spelunker and other), M75 (Vigilante) and M72 (on some  type of ‘M72-B-D board) hardware

As usual I reproduced it my way by observing how it was reverse-engineered on bootleg boards obtaining in a board layout with pretty same dimensions of original part :

Testing on a Kung-Fu Master PCB :

 Posted by at 10:26 am

The New Zealand Story repair log #5

 PCB Repair Logs  Comments Off on The New Zealand Story repair log #5
Aug 022019
 

Received for repair from New Zealand this The New Zealand Story PCB (sorry for the wordplay…), the one layer hardware revision :

Board booted up but graphics were totally wrong :

GFX data are stored in eight 28 pin 1Mbit MASK ROMs whose pinout is pretty identical to 32 pin 1Mbit non-JEDEC EPROM (extra pins apart)

Before dumping them I used my logic probe and found stuck upper address lines (pin 12-13-14-15)

I traced the address lines back to outputs of a 74LS174 @U9 whose inputs were floating, these came from a Fujitsu 74LS374 @U41:

Inputs of it were toggling but all outputs were stuck at undefined voltage level of 1.48V, this is the typical way of failure of Fujitsu TTLs :

The chip failed the out-of-circuit testing, all outputs were indeed in ‘Z’  (or high-impedance if you prefer) state :

Once replaced the IC the graphics were restored but I noticed some corruption on title screen :

I dumped the 1Mbit MASK ROMs and my programmer complained about the one @U7  :

This was a good chance to use one of my adapters I designed some time ago for replacing the 28 pin 1Mbit MASK ROMs with a TSSOP Flash ROM

But suddenly during power cycling the graphics went bad again :

I quickly pinpointed the fault to another 74LS374 @U10 with floating outputs, another Fujitsu one obviously :

Chip totally failed the out-of-circuit testing:

Graphics were now perfect so I started a game but controls didn’t work, the main character of both players moved by itself:

 

Looking at hardware I figured out the I/O circuit.The inputs from JAMMA connector go to some custom resistor arrays marked ‘X2-005’ and then signals are routed to a 52 pin SDIP custom chip marked ‘X1-004’ that handles them :

Resistor arrays did their job by pulling-up the signals and then routing them to the custom so most likely the ‘X1-004’ was bad.I played the card of replacing it but I had to struggle before finding a good spare as it seems this custom is quite prone to failure.I tried two donor parts but they were faulty until I caught the good one:

This fixed the controls and board completely.Repair accomplished.

 Posted by at 9:25 am

Konami ‘083’ reproduction

 Reproductions  Comments Off on Konami ‘083’ reproduction
Jul 262019
 

This is another ‘poor man’s’ custom IC reproduction I made with no use of CPLD or other complex programmable logics.The part reproduced is the Konami ‘083’, a 28 pin 600 mil in DIP package which most of times comes with scratched-off part name :

It can be found on several Konami PCBs, you can refer to this useful spreadsheet (credits to ‘mattosborn’ on KLOV forums)

https://docs.google.com/spreadsheets/d/1iB9BJaEpAufgKaz758FiDDekUH8JreoTn276yPqD-kk/edit#gid=0

As always I observed how its functions were reverse-engineered on bootleg boards and made my own reproduction with simple TTL gates logics :

Final successful testing on a Mega Zone PCB:

 

 Posted by at 11:05 am