Technical InfoComments Off on Commodore 64 Game Killer cartridge
Dec152016
Found this oddity on eBay not too long ago.
Its a crude device that attempts to disable collision detection for games that used hardware sprites.
It device itself wasn’t too successful but it was cheap and love my C64 so here it is.
I spend half an hour drawing up a schematic for the device and also dumped the ROM which is in the downloads section.
Cant imagine anyone ever needing to use the schematic for anything. Its very simple and any fault finding could be done in moments and who in the right mind would want to create more of these things but it was a small side project.
PAL UpdatesComments Off on Kaneko Super Nova ROM board PAL dumps added
Oct232016
Found two ATF16V8 PLD’s in a Super Nova ROM cartridge. Both were unlocked but have not been verified as my PCB has a fault. The equations look good.
The ROM board is marked ROM-2.
This Thunder Cross II board was stuck in a watchdog cycle.
A quick visual inspection showed this
It was easy enough to bend this back a little without causing any damage.
Powering up the game, it would sometimes show the RAM/ROM test screen from the POST with failures reported and sometimes it would just reset straight away showing nothing.
Using a logic probe I quickly found the RAM at 1H and 16E were bad both of which had completely dead output pins.
I piggy backed a known good working 6116 RAM chip on top of both of these and while it didn’t cure all my problems, on the time it booted to the test screen these RAM’s now showed clear.
I replaced them and moved onto the resetting issue.
The reset on this board is handled by a custom SIP package. I was fairly sure this wasn’t to blame as on the occasions it booted up, if I held the TEST button down to reinitialise the EEPROM the game did not reset throughout the initialisation.
I did notice a 4.7k resistor array was missing.
I replaced this but it made no difference.
Next I noticed the game booted up more regular if my hand was on the 68000 CPU. Things like this are a good indication that there is a floating pin somewhere. Probing the CPU pins revealed that pin 21 of the 68000 (/VPA).
Chasing this proved difficult as there was a broken trace somewhere but these Konami boards have really small thin traces and vias. I eventually traced it back to pin 6 of a 74LS20 at 5E1.
Jumpering this gave me a booting game.
Everything initially looked good, the attract mode played and the sound effects were present. The problem came when some music played. To start with it sounded terrible but once the music stopped all the sound effects were either messed up too or were missing altogether.
I fired up the test mode and did a ROM check which game me this
or sometimes this
I had verified the ROM which checked out OK and sound effects were present. The music also attempted to play so I was fairly sure the CPU and ROM were good.
I started looking at how the MASKROM was addressed and how the PASS/FAIL data was send back to the main CPU. This all led me to the 053260 custom chip at location 5E
I mapped out all the address and data line to the MASKROM and noticed that anything after address line A10 was dead. Looks like we have a dead custom.
As it happens I found a scrap Konami PCB in the loft from which I could harvest this chip from.
Replacing this gave me my sound back and the ROM tests now all pass.
Got a bunch of boards from Olly to attempt to repair. One of them is a tiny New Zealand Story PCB.
There is a broken custom resistor array on this PCB. Turns out this SIP is for DAC for the green colours.
Not really sure how this could have happened. Caius is sending me a replacement for it but it plays no further part of this repair.
I powered up the PCB and this is what we get
The game plays blind behind this wall of garbage so we know the CPU is doing its job.
The board has quite a few Fujitsu TTL chips on it so my first bets were on failed TTL. The PCB is also tiny which makes this job pretty quick.
In my experience of failed Fujitsu chips I found that pins go completely dead and this PCB was on different. I found a couple of 74LS374 chips at U41 and U10 with dead outputs and these are easy to spot with a logic probe.
As the outputs were dead I could quickly test by ‘piggybacking’ a known good chip on top of it. The changes were good enough to confirm.
I replaced these two chips.
Replacing them did give a big difference and I could now see all the outputs from those two chips were once again active. The graphics were all messed up still.
Next I see that one of the MASKROM’s has been replaced. They are 23C1000 compatible and therefore there is no 28 pin EPROM replacement available. It has been replaced with modified a 27C1000 chip.
This mod is not part of the problem.
I pulled all the other MASKROM’s and dumped them. 4 of them actually failed so in the short term I replaced them with modified 27C301 EPROM’s.
All the graphics came back good.
There is a 128×8 ROM replacement PCB available from OSHpark shared projects made by system11 so I downloaded the Eagle board file, added a little TNZS graphic to it and ordered some up. The A298010AV chips however are really quite hard to source so Ive got to wait until February before these come in from back order!
As it stands now the game is fully playable with only the green colour issue. I will replace the resistor array SIP once it gets here.
There Is a calculation outlined in the manual around predicting the life expectancy of the tube and ive made a little spreadsheet up to deal with that.
The calculation relies on being able to set the G1 voltage on the pot.
I noticed when I first got this that when I adjusted the G1 pot it was pretty loose feeling and also the reading bounced around everywhere.
Fast forward a year and I’ve come to use this again. I was completely unable to get accurate steady results from the G1 this time so I went to check the pot and found readings like this
I tried cleaning it out with contact cleaner but its had its day.
I ordered a new 250k pot from CPC and it came a few days later
Fitting this gave me solid results from the G1.
One thing I recently noticed about this rejuvenator is it has a switch marked “Soft” and “Strong”. Id not really noticed anything wrong with this before but the BMR 95 doesn’t have this option normally. It is present on the BMR 2005 model though.
Looking at it inside it looks to be a factory mod. The same wiring was used and its all part of the same loom. All solder joints look factory as well. Its either a factory mod or a very well done aftermarket mod. Either way Im pretty sure this give me the functionality of the BMR 2005.
