Pitfall II : The Lost Caverns repair log

Received some days ago for repair a Pitfall II PCB (on Sega System 1 hardware)
Board was in very good condition :

But on power up it gave only a solid black screen and nothing more hence deeper troubleshooting was needed.Probing the main CPU/RAM/ROM circuitry revealed that the lowest address line (A0) was stuck high on the three program ROMs and nearby RAM :

ROMs and RAM are addressed by the main CPU (a custom Z80) not directly but thru some 74LS244.I traced the stuck address line back to an output of the 74LS244 @IC124 which, according to my multimeter,  was shorted to +5V :

I was almost sure the TTL chip was bad (it was from Fujitsu too) hence I removed it but it turned out to be good.So there was something else shorting the address line to VCC preventing the game to boot.I flipped the board over and traced on solder side the shorted address line back from the ROMs/RAM.While I was following the traces I came across this :

A close-up under the microscope :

A VCC pin was bended on the nearby trace of the address line peeling-off the solder mask and causing the short, unbelievable!I promptly straightened the pin and board sprang to life :

I played some games, no further issues were present, board was 100% working.Another successful repair accomplished.

Sega '315-5242' reproduction

The '315-5242' is a custom IC used on some Sega arcade systems :

• System C/C2
• System 18/24/32
• System X
• System Y

It's basically a video DAC connected to the color RAMs, which provides analog outputs for driving a monitor.It accomplishes also some special functions like making the video output grayscale instead of color or enabling shadow/highlight effect.It comes under the form of a ceramic module covered by black paint or epoxy :

The 'core' of the '315-5242' is a surface mounted IC (PQFP44 package) located on top of the module, the 'M71064' from OKI manufacturer :

No info or reference was available for this fully digital IC until some time ago when 'furrtek' decapped it and traced schematics from the silicon die revealing the internal structure and figuring out the functions :

Most of the work was done so the step to a real replacement was the easy and logical consequence.And here we are!I designed a proper board based on a +5V CPLD :

Testing on all boards I could try was successful.


Columns II (System C2)

Michael Jackson's MoonWalker (System 18)

Spider-Man (System32)

Thanks again to 'furrtek', without his brilliant work none of this would have been possible.

Toaplan 'HK-1000' reproduction final revision

As many of you may know I made some time ago a reprodution of the 'HK-1000', a custom IC used on some PCBs manufactured by Toaplan :

Toaplan ‘HK-1000’ reproduction

The replacement was welcomed by arcade enthusiasts and collectors who used it to repair faulty boards but actually it was not a 1:1 replica of the original chip because the handling function of the coin counters/lockouts was missing since I intentionally omitted it, not considering it of primary importance. 

For the uninitiated a coin counter is mechanical style counter that increments every time a coin is inserted, here's picture of a +12VDC powered one:

Lockouts are, instead, a mechanism to prevent users from wasting an inserted coin when the cab is off or not properly operational.

Lately I've been ask more than once to implement in my 'HK-1000' reproduction the circuit needed to add these missing functions.And here we are!!This will be the final revision of the replacement, all functions of  the original chip have been implemented in it.Outwardly it has not changed from the previous ones :

  
But from now on it will be finally possible to properly use a coin meter in your arcade machine when you play those particular Toaplan boards using my reproduction :  : 

Data East 'VSC30' reproduction

Some time ago I had for repair an original Bogey Manor PCB by Technos (but running on Data East hardware).I was able to fix the board but I had to replace the custom IC marked 'VSC30 with a same one taken from a donor board, you can read the whole story in my repair log :

Bogey Manor repair log

After some time I sent the board back to the owner I  thought it would have been a good thing to reproduce this custom IC as well.The part come in a DIP40 .600 mil package :

Its pinout can be found in schematics of different Data east games like Express Raider, Last Mission and Gondomania :

It seems the part is involved in tilemap/background generation performing some kind of clock dividing.With this info and looking at how the same functions were achieved on previous hardware I came to a couple of designs using simple TTL gates ( I even used DIP ones because of low number needed)

I used as testing platform my original Express Raider PCB which carries one 'VSC30' on bottom VIDEO board :

The replacement worked great :

As far as I know the 'VSC30' is present on these PCBs :

• Bogey Manor
• Breywood
• Express Raider
• Gondomania
• Last Mission
• Shoot Out
• The Real Ghostbusters

And perhaps some others running on similar Data East hardware of same era (see 'dec8.ccp' driver in MAME soruce) so feel free to send your findings.Also, it could be that few boards, like Bogey Manor, make use of extended features of this custom IC so, please, contact me if you are willing to test my replacement on your board.