While searching through some documents from Data I/O I came across a bunch of logic diagrams for various PLD’s. One of them was for the CK2605.
As I’ve not seen this in the wild before I thought I’d upload it.
*click the picture for PDF
Received for repair this original Wonder Boy III – Monster Lair PCB (on Sega System16B hardware)
Board booted into game but sound was missing and some objects glitched :
I decided to troubleshoot for first the lack of sound.The amplifier was previously replaced as well as some electrolytic capacitors:
Using my audio probe I could figure out that the lack of sound was not caused by a fault in the analog circuit but it had a digital nature so I went to check the relevant circuit made of a Z80B CPU, a 6116 SRAM, a ROM and a YM2151 (plus a UPD7759 for speech samples) and I found that pin 15 (data line D5) of the RAM was silent as well as on the respective data bit of the Z80 and the YM2151 :
But it was toggling on the ROM (a 27C512 EPROM) which lies on ROM board :
There was clearly a broken trace somewhere so I run a jumper wire from the RAM to the ROM:
This restored the sound.
Now the sprites issue.Relevant data are stored in eight 27C512 on ROM board :
I dumped the devices and my programmer complained about a bad contact on pin 9 of the EPROM @B2 and pin 16 of the one @B7:
At a closer inspection it turned out the pins were cut so they didn’t make a good contact into sockets:
I rebuilt the pins and this fixed the sprite issue.Board fixed.
Received from USA this mint Contra PCB (by Konami), actually with japanese stickers and ROM set :
The board kept resetting in an endless loop sign that CPU was executing no valid code hence the watchdog circuit was triggered:
The two program ROMs were dumped as good so problem was elsewhere.Board was almost fully populated with Fuitsu TTLs which are well known to be prone to failure.When probing them with a logic probe I found a floating output (pin 11) of a 74LS08 @17D:
This was confirmed also by logic analyzing and scope:
As schematics shows, the missing signal from pin 11 is called VRC and it should be a control line routed to the custom ‘007452’ :
I removed the TLL and tested it out-of-circuit where it failed miserably :
I installed a socket and fitted a good IC:
The board booted into game with no further issue.Repair accomplished.
Received for repair this original The New Zealand Story PCB (one layer hardware revision)
Board played fine except for this issue concerning background graphics, they had jail bars though :
All GFX data are stored in eight 1Mbit 28 pin MASK ROMs :
I dumped them starting from the one on the right labeled ‘B53-01’ :
And my programmer complained about a bad contact of pins 18-19 (which are data lines)
As said the device is a 1Mbit 28 pin MASK ROM which no direct replacement exist of, the only option is to adapt a 1Mbit 32 pin EPROM (better with non-JEDEC pinout), that’s what a made :
Perhaps not the best looking solution but it fixed board completely.Job done.
P.S.
This repair inspired me so I made my own design to adapt a 1Mbit 32 pin TSOP Flash ROM to the 28 pin 1Mbit MASK ROM pinout:
Some time back I bruteforced the A-17480 PAL16L8 chip from Mortal Kombat II. This was untested until recently when UKVAC member JonHughes tested it and found it didn’t work properly.
We tried several things but always got the same issues so he sent me his full PCB to do some testing of my own.
While I could find anything wrong from an operation point of view I did find that the original TIBPAL16L8-10 PAL chip transitioned states about 4ns faster than the fastest GAL chip I have to hand. I had experimented with GAL’s ranging from 10 to 25ns but the slower ones did just make the issue worse.
In desperation I ordered a NOS TIBPAL16L8-10 from eBay (not too cheap these days) in order to be 100% sure of my work. The result was a perfectly running game.
So what are the issues? Well not a lot really. A GAL substitute will still allow the game to play very well but it did show errors during the POST
The game itself also plays fine but there are some graphical issues here and there, most noticeably on the ground during actual gameplay.
On the video you can see the ground keeps glitching black. This is pretty much the only fault I can see but its definitely worth noting
The video is not the best quality, capturing CRT screens with my phone is never great but hopefully you can see.