Another PAL update today.
Yves M sent in a complete PAL dump set from an Heavy Unit original PCB while Layer an handcrafted GAL16V8 made to work with Street Fighter Zero / Alpha CPS Changer running on a CPS-1 91634B-2 B-BOARD.All dumps have been tested as working in GAL16V8 targeting devices.Thanks to both for their work, we highly appreciate it.
Another board from my friend ‘robotype’, this is the time of a genuine Sega Out Run:
Once powered up I was greeted by a colored stripes static screen:
Since I already repaired an Out Run board with same issue I remebered that this is a symptom of active watchdog and infact this was confirmed by probing RESET and HALT pins on main 68000 CPU.I wanted to use my Fluke 9010A troubleshooter but due the presence of a custom memory mapper between main CPU and RAMs (which, indeed, generates dinamically the memory map on boot) I wasn’t able to do it.
For first I read the four program ROMs and they were good.So I went to probe the CPU/RAM/ROM circuit and I found many CPU address lines tied LOW or HIGH.Piggy backing the two 74LS244 @IC136 and IC137 didn’t change nothing but when I did it on the two TMM2063 (6264 compatible) WORK RAMs @IC115 and @IC130 I got this screen in which I could descry the welcoming message of a successful boot:
This lead me to desolder the two RAMs which were confirmed as faulty from my tester
So I could enjoy again the Magical Sound Shower!
Im still working on Gameking things when time permits.
Team Europe has also started to dump new Gameking games and up until recently we have had no way to test our dumps.
I have now made a multi game cartridge for the Gameking which can hold 4 128KB size games and are selectable via two dipswitches.
So far all the games we have dumped seem to work just fine although Team Europe has recently dumped an actual multi game which will NOT work on this board.
I realise that there wont be many people in the world that would want one of these but if you do I currently have 4 spare for sale at £10gbp + postage fully assembled with blank flashROM.
Today it’s time to do some PAL updates.
Our finest contributor ‘coolmod’ sent in dumps of two unprotected devices (PAL16L8 and PAL20L8) from a Galmedes PCB (which runs on TAITO Bonze Adventure hardware). I took care of converting them to GAL format (both GAL20V8 and GAL22V10 conversions available of the PAL20L8) and he successfully tested them on his board. Thank again to him for this contribution.
Today I received a Gaplus PCB and tried both the MAME dump and the one on our database but neither worked so I dumped device (there is no part name but it should be a PAL16L8) from my board. Dump is tested and working in a GAL16V8 targeting device.
I had this PCB since many years, honestly I couldn’t remember when I got it or where.The only sure thing is that it was faulty.Condition was pretty good for a such ‘aged’ board but it was missing a BPROM @IC101 as you can see:
Original part is a Fujitsu MB7114, pretty impossible to find nowadays so I opted for a 82S129 which an equivalent one.After burned the device with the correct file supplied by MAME, I powered on the board and some times it got stuck on RAM/ROM TEST showing error on WORK RAM:
Other times it booted into game but sprites were missing, could not coin up, screen was unstable and speed was kinda accelerated.When I got this strange behaviours, the fist thing I check is the main CPU, in this case an Hitachi HD63C09.Probing it I found that PIN2 and PIN4 were stuck LOW, they are respectively the NMI and FIRQ interrupt lines:
So this meant that CPU was undergoing a request of interrupt from external devices (an interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention).As you can see from the above schematics these two signals are generated by a 74LS74 @IC73 so for first I went to check it and I found missing CLOCK and CLEAR signals input on PIN3 and PIN13 respectively.In particular CLOCK on PIN3 is the VBLANK signal and this is generated by a NAND gate of a 74LS00@IC70 on VIDEO board :
Comparing it in-circuit revealed it was faulty:
Once replaced it I got no more WORK RAM error and strange behaviours, game was playable but all sprites were missing:
This a common fault on all Double Dragon PCBs since object generation circuit is wide and made of many components (it occupies five sheets of the .PDF schematics).
So, following the schematics I checked this part of circuit and all was fine until I came across to this section:
The 74LS86 @IC72 had stuck outputs and these are tied to some ADDRESS lines of a TMM2018 SRAM which had some silent DATA lines, too.So I prontly desoldered them and they failed once tested out-of-circuit:
I thought my job was done but I was wrong since this improved the sprites but not fully restored as they still missed some lines symptom of missing DATA:
So I kept to check the OBJECT circuitry until I come across the TMM2018 SRAM @IC20 which had four silent DATA lines (PIN14-PIN17).I piggybacked it and magically all sprites were restored:
PCB 100% fixed and another one preserved!
Just a note for future reference : there are five TMM2018 (6116 equivalent) sprites RAMs and they are @IC73, @IC81, @IC84, @IC120 and @IC7 on VIDEO board.