28 Feb 2018

Heated Barrel - TAD 1992 (Repair log #2)

Same board repaired previously back on the test bench.

Again with wrong colours:

The second palette RAM @ F4 has died. It's not rare form RAMs working in pair to die at very short interval. Anyway, once replaced issue was fixed:

Game fixed.

21 Feb 2018

Pang - Capcom_Mitchell 1989 (repair log)

Game had committed suicide. This hardware should display a plain light blue screen when suicided but this one gave nothing, no sync signal: sure there was more work than just burning the decrypted ROMs and adding few wires.

Anyway board was covered by a greasy liquid I reckoned was CRC or WD40. No idea why...
So first I removed the socketed chips and it went in the sink for a bath:

Once dried I followed the desuicide procedure found on the "Dead Battery Society" website (http://www.arcadecollecting.com/dead/), and then fired the board: nothing, no sync just as before.
I probed the main CPU and found no activity at all, not even a clock. So I moved to the crystal and it was pulsing fine, however on the part side I found a ferrite with a broken leg. This ferrite was connected to the output of the crystal so that was sure a big issue:

I replaced it:

And the game booted to a corrupted title screen:

Well this time I was responsible for it, I read PW on the ROMs (for Pomping World = Japanese version of Pang) so I used the Japanses decrypted ROMs. What I missed was some ROMs had PWE written on them: this was the World version of the game hence Pang. I burnt new ROMs with the World version decrypted ROMs and title screen was now correct:

However text layer was missing...

By probing few chips I found no activity on one of the outputs of the LS157 @ 7E. Inputs were not pulsing either: one was connected directlty to ground and the other lead me to another IC. Again no activity on both concerned output and input. I followed the signal from one IC to another and finally while tracking it down I found a trace has been severed and made connection with a pad nearby:

I removed the unwanted connection and the game played 100% correctly:

Game fixed.

14 Feb 2018

Conversion SF2' to The Punisher (CPS1 no Q-sound)

After the Cadillacs & Dinosaurs conversion I thought i would be worth it to have a try at The Punisher. I've used the samples of The Chinese bootleg version named Biaofeng Zhanjing which are in fact Final Fight samples.

1) Material needed

1.1) If you use a 91634B-2 B-board (EPROM)
 - 12 * 27C4096 ROM (8 for the graphics and 4 for the program)
 - 2 * 27C010 ROM (audio)
 - 1 * 27C512 ROM (audio)
 - 1 * GAL16V8 (PAL)

1.2) If you use a 91635B-2 B-board (mask ROM)
 - 8 * 27C400 ROM (graphics)
 - 4 * 27C4096 ROM (program)
 - 2 * 27C010 ROM (audio)
 - 1 * 27C512 ROM (audio)
 - 1 * GAL16V8 (PAL)

2) ROMs and PAL burning

Now it's time to burn the files on the appropriated devices.

2.1) If you use a 91634B-2 B-board (EPROM)
 - ROMs 01/02/03/04/05/06/07/08/20/21/22/23 => 27C4096
 - ROM 09 => 27C512
 - ROM 18/19 => 27C010
 - PS63B_1a.jed => GAL16V8

2.2) If you use a 91635B-2 B-board (mask ROM)
 - ROMs 01/02/03/04/05/06/07/08 => 27C400
 - ROMs 20/21/22/23 => 27C4096
 - ROM 09 => 27C512
 - ROM 18/19 => 27C010
 - PS63B_1a.jed => GAL16V8

3) ROMs installation

All SF2' ROMs must be removed from the B-board.
The PAL named S963B at position 1A has to be removed too.
Double check you've put the devices the right way (the silkscreen should help you)!

3.1) If you use a 91634B-2 B-board (EPROM)
 - Install the ROMs in the corresponding socket (ROM 01 in socket 01, etc.)
 - Install the GAL16V8 in position 1A (where the S963B was)

3.2) If you use a 91635B-2 B-board (mask ROM)
 - Install the ROMs 01/04/05/08/09/18/19/20/21/22/23 in the corresponding socket (ROM 01 in socket 01, etc.)
 - Install ROM 02 in socket 03
 - Install ROM 03 in socket 02
 - Install ROM 06 in socket 07
 - Install ROM 07 in socket 06
 - Install the GAL16V8 in position 1A (where the S963B was)

4) Test

7 Feb 2018

Conversions on Jaleco Mega System 32

A not too well known system with only few titles but with great graphics for some of them.
It can be considered as Jaleco's answer to SNK's MVS as this system is composed of a mainboard in which you plug "cartridges" (which are more or less romboards with a plastic shell). Connection between the 2 isn't as easy as it is on MVS cause Jaleco didn't use edge connectors for its cartridges but high density connectors instead (similar to Capcom's CPS1 and CPS2 for instance).

Anyway, to prevent conversions, Jaleco implemented a custom chip in the cartridges for graphics decryption (texts and background only) with different decryption "parameters" between games. Some games share the same custom chip, thus can be converted straight forward, some others don't and even different versions (romsets) of the same game can use different custom chips.

Decryption algorithm being in MAME I first decrypted the files for gfx3 (background) and gfx4 (texts) for romset gratia (custom chip ref. SS92047-01). Then I made a second small piece of code for re-encryption. I chose to rencrypt the files for custom chip ref. SS92046_01 as it's used on Tetris Plus (romset tetrisp) and this game is quite common and cheap.

Finally I modified MAME's source to force it to use a different custom chip with romset gratia.

I changed this:
GAME( 1996, gratia,   0,        ms32, gratia,   ms32_state, ss92047_01, ROT0,   "Jaleco", "Gratia - Second Earth (92047-01 version)",

To this:
GAME( 1996, gratia,   0,        ms32, gratia,   ms32_state, ss92046_01, ROT0,   "Jaleco", "Gratia - Second Earth (92047-01 version)",

And tested the conversion successfully:

Next step is to test it on real hardware and maybe find a way to use decrypted files instead of re-encrypted ones to simplify things (no need to re-encrypt files for each different custom chip).

1 Feb 2018

Capcom 85H001 (sound module) reproduction - part 1

This module has been a real nightmare for me for years as its failure rate is quite high...
Unfortunately to save a game you have to sacrifice an other one as there's only one module per game.

I know of 3 different flavours (there might be more) which are interchangeable between games (I tested it personally) :
- Ceramic module without any marking: seen on Makaimura first run for instance
- Plastic module ref. 85H001 5I
- Plastic module ref. 85H001 5H

Affected games are (from the top of my head):
- Ghosts'n Goblins/Makaimura
- Avengers
- Legendary Wings/Aresu no tsubasa
- Section Z
- Trojan/Tatakai no banka
- Gun Smoke
- Black Tiger/Black Dragon

I already designed a replacement module which I tested on Trojan and GnG based on my observations and schematics of earlier games but I couldn't guarantee it was a 100% perfect replacement.
So recently I took the decision of decapping the ceramic module of my Makaimura first run (as it seemed a lot easier to me to dissolve ceramic rather than plastic).

Before soaking it in a basic (soda) solution I removed with a sharp knife the ceramic layer on top on each IC to be able to read references in case the soda washes them out (which it did!):

The module after a 24h soda bath (I added references):

I then drew the schematics and assembled a prototype with through hole parts:

And tested it successfully on real hardware!

Next step is to route a board the exact same size the original one with SMD parts.
Stay tuned!

The prototype tested on Trojan: