GeneralComments Off on Jaleco ‘JK-03’ reproduction successfully tested
Some time ago I made a reproduction of the Jaleco ‘JK-03’ custom SIL used for inputs handling on some Mega System 1 PCBs but at that time I was not able to test it due to the lack of a proper PCB hence I asked for some volunteers.You can read the post here:
Today I can report the reproduction is fully working thanks to the test carried out from the user ‘Astro X’ of AP forums on his Saint Dragon PCB with missing ‘JK-03’ (actually an hack was installed as workaround) :
I received for repair a quite rare original Spelunker PCB (on Irem M62 hardware).Board is a three stack one made of a top board (which carries most of sound hardware) :
A middle CPU board (specific for each M62 game) :
And a bottom VIDEO board :
The PCB had severe GFX faults, the sprites were only lines vertically stretched all over the screen:
All the sprites circuit lies on bottom VIDEO board which is the same for all games that run on M62 hardware.Looking at Kung-Fu Master schematics I could figure out that data bits from sprite ROMs are fed into the custom marked ‘KNA6034201’ :
The inputs were all active but most of outputs floating:
So the custom was most likely internally faulty.Luckily I have done a reproduction of this component some time ago.You can think of it like a 24-bit parallel to serial shift register:
I removed the custom and installed the reproduction:
The sprites were back but not perfectly as they were lacking of lines and misplaced too:
The sprite line buffer consists in two 2k x 8-bit static RAMs (Toshiba TMM2018 used here) :
Probing them revealed on both a floating address line (pin 1, A7) :
Address lines are generated by the surface mounted custom ‘KNA6074601’ :
Its pinout/implementation from Kung-Fu Master schematics :
I had no other choice than replacing this part so I asked the owner to look for a donor board.He found and sent me a Vigilante PCB which carried the ‘KNA6074601’ on bottom board :
I removed the faulty one and soldered the spare back :
I have two Toki pcbs in storage, both with sprite errors. I saw a video from lukemorse1 (who actually inspired me to start repairing arcade pcbs) on youtube where he worked on a Toki pcb, also with sprite errors.
Here’s how the error on board #1 looked like:
So there are blocks surrounding the sprites.
From Luke’s video (https://youtu.be/Czdt_yTNRTs) I identified the area responsible for sprite handling and I quickly found a 74LS273 with a stuck output at pin 19:
Checking with the multimeter, I found that this pin was almost shorted to ground:
I quickly desoldered the IC and tested it with my VP-398
Replacing it with a working 74LS273 made the sprites appear as they should:
So a big thanks to lukemorse1 and also as always to caius for always helping out 🙂
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.
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.