Taito 'TC0220IOC' reproduction

The Taito  'TC0220IOC' is a custom IC manufactured by Taito, used across their arcade hardware (such as Taito Z, F2 and L systems ).It comes in a QFP80 package.

Technically speaking it's an Input/Output (I/O) and reset controller: it manages I/O operations and provides the master reset signal.It's not a ery reliable component, a frequent cause of damage is plugging a JAMMA harness backwards, which can route +12V into the chip and fry it.And if this happens, you’ll end up with a completely dead board in your hands (with no or stuck reset signal output coming from pin 8 of the chip).In this case nothing can be done to by-pass the chip since it handles also some data and address lines from main CPU as you can see from pinout (taken from Final Blow schematics).

The only chance to fix a board with a faulty 'TC0220IOC' would be find a spare part from a donor board but you have to sacrifice a working board most of times.Someone had some luck finding NOS or pulled parts from electronics suppliers but you may risk to get counterfeits, mislabeled chips, or dead-on-arrival components.So, I took into account to study some kind of replacement.As always I do I looked at previous hardware where the functions of this chip were accomplieshed by simple TTLs gates (later they embedded the logics into a single chip).The main obstacle for a replacement of a surface mounted part (QFP80 in this case) is how to interface it on the original fooprint but, like other projects of mine, castellated half holes design was the right solution.The 'hearth' of the reproduction is a little CPLD running the logics I reverse-engineered.

The replacement worked good at first try when I tested it on a Crime City PCB.

Another custom IC preserved and a way to save boards that would otherwise be often beyond repair.

Mr. Do's Wild Ride repair log and Texas Instruments TMS1025N2LC reproduction

Got for repair this original Mr. Do's Wild Ride PCB, a platform game developed and published by Universal in 1984 and the third installment in the classic Mr. Do! series :

Board booted up, game was playable with sound but there were jailbars over the sprites :

GFX data are stored in four 2764 EPROMs

Jailbars most of times denote an issue with data bus so I looked at schematics of Mr. Do's Castles (which shares same PCB layout).Data lines of the four GFX EPROMs are directly connected to a 74LS374 @D5 :

Probing the 74LS374 (with a logic probe) revealed a stuck output (pin 5) while its input (pin 4) was regularly toggling :

Sure enough I removed the IC and tested it out of circuit, it failed exactly in that output :

Installed a good IC with rounded machine tooled socket :

 This cured the sprites issue, jailbars were gone away, board was 100% working now :

Before archiving this repair I wanted to carry on a little project to reproduce one of the custom IC found on this board (and other PCBs from Universal).The part is marked 'TMS1025N2LC' manufactured from Texas Instruments, there are a couple of them on Mr. Do's Wild Ride :

This custom IC is used to handle all the inputs (including dipswitches) as shown in schematics :

There are very scarce information about this IC but, as often I do, I managed to source a bootleg PCB where the this part was replaced by a little sub-board made of simple TTL logic gates.It was only matter to draw schematics of this sub-board and design with them a proper replacement board based on a little CPLD :

The replacement worked fine at first glance.Another repair completed and another custom IC preserved.