Toaplan ‘HK-1000’ reproduction

As many of us know (not only long term arcade collectors/enthusiasts) Toaplan manufactured few but excellent games.Some of them can be considered real masterpieces like Out Zone and Truxton for example.Going into technical details four of them are united by the fact the hardware uses a custom IC to handle inputs: the  ‘HK-1000’.I have partially covered this argument in my past repair log of Tatsujin Oh, you can read it here:

Tatsujin Oh repair log #1

As said in the above post, two revisions of the HK-1000 were made with same functionality but different package.The first one was ceramic hence very fragile.This is used on Truxton II/Tatsujin Oh and FixEight:

The second one is more robust and it’s adopted on Ghox and Pipis & Bibis :

If this custom goes bad (like it happens very often especially on first revision) you will be no longer able to fully control the two players and in the worst of cases the board will be stuck on a TILT message.The only option could be find a donor board but we are speaking of valuable PCBs even if faulty.So some kind of replacement was needed.

There is very few info and documentation about this custom but it seems Toaplan engineers embedded on a single IC (the HK-1000, indeed)  all the circutry they used to  handle inputs (but also coin counters/lockouts) on previous PCBs  (Wardner, Out Zone, Rally Bike and others too).I took inspiration from an Out Zone PCB to study the design:

As you can see from the above picture, I highlighted two sections of PCB : the blue one concerns the circuitry for coin counters/lockouts handling, the red one is for inputs (players direction and buttons, TEST, SERVICE, TILT).With this knowledge I started my tests.As testing platform I used a Pipis & Bibis PCB (the cheapest one which carries the HK-1000).I removed the custom and mapped some inputs following the above mentioned design:

This was successful so I started to draw and route schematics for a real replacement.I voluntarily omitted from my design the circuitry for coin counters/lockouts as it’s not a vital part (although I figured it out so I can implement it in a later moment).I sent the layout to a manufacturer and after few days I received the bare PCBs:

 

Very few components are needed to populate the PCB :

• Three 74LS240 in SOIC20 package
• Three 100nF ceramic by-pass capacitors in ‘0805’ package
• Three (two 9 pins and one 8 pins) 4.7Kohm SIL bussed resistor networks for inputs pull-up (I opted for thru-hole ones to keep cost down, they can be salveaged from arcade PCBs)
• Two strips of 24 pins male rounded machine-tooled pin header with 2.54mm of pitch.The corresponding female ones must be used on the arcade PCB.

Here is final result after 5 minutes of soldering:

A comparison with original custom:

Testing on the Pipis & Bibis PCB was successful, all inputs of both players were correctly mapped and working as well as TEST, TILT and SERVICE ones:

As said, this is not a 1:1 reproduction of original part since coin counters/lockouts handling has been not implemented for now but it’s enough to salveage your faulty boards from uselessness.Stay tuned for the next reproduction project!