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This DECO boardset uses a 6502 driving a YM3812 FM synthesizer, and probably an ADPCM chip for the sound effects.

The links below will net you RealAudio (ISDN) versions of most of the music from the game. As with Robocop, I had to use a special test clip on the board to freeze the game and record the music. However, it was worth it; the music from Heavy Barrel is VERY good. I believe the same person who wrote Robocop's music was employed on this game. The level 1 theme is particularly enjoyable.

realaudio music:
Level 1 Music (382K)
Level 2 Music (363K)
Boss Music (176K)
End-Game Music (457K)

Interestingly, almost all of the spot effects (gunshots, "aargh!" noises, explosions and grenade-hurling effects) in Heavy Barrel are the same as those used in Robocop. Many of the weapon graphics are the same too, despite Robocop being a side-on-perspective game.

End-Game Message:

CONGRATULATIONS!
YOU HAVE ACCOMPLISHED
YOUR MISSION.
DISMANTLE YOUR SECRET WEAPON.
YOU SAVED THE LAND
FROM DISASTER.

THANKS FOR PLAYING
DATA EAST USA,INC.

STAFF

GAME DESIGN
KOJI AKIBAYASHI

PROGRAMMING
MEN TAIKO
NOBUSUKE SASAKI
NAOMI SUSA
SATOSHI IMAMURA
TOSHINARI UEDA

GRAPHIC DESIGN
J.S
BACK MAN
MASANORI TOKORO
T.ADACHI
YOSHIYUKI URUSHIBARA
MIX MAN

MUSIC AND SOUND
ASUZA HARA
HIROAKI YOSHIDA

HARDWARE DESIGN
JUNICHI WATANABE
KENICHI FUJIMOTO
HIROYUKI IWABE

Heavy Barrel Gun SoutheastHeavy BarrelHeavy Barrel Gun Southwest

Heavy Barrel is a moderately rare top-down perspective commando attack type of game rather like Ikari Warriors. It uses rotary joysticks to aim the player weapons independently of the direction they're moving - which allows the player to do a lot of skilful things, but requires a lot of practise to master.


A rather nice scene from level 1, with scrolling water underneath a wooden bridge. Heavy Barrel has great parallax scrolling effects (unlike Robocop and Dragon Ninja, which barely use the multilayer support offered by the DECO hardware).

Repair Info

My Heavy Barrel board was bought as non-working. On power-up, I got a blue screen and nothing else. I verified that the lower (ROM/IO) board was OK by swapping it onto my Robocop top-board - that allowed me to play Heavy Barrel to my heart's content. However, I wanted to get the whole thing working so I wouldn't have to go swapping ROM boards all the time 8-)

First step was to go over looking for broken-off components. At A17 there is a 12MHz xtal which clocks the video ASICs. Here, a plate capacitor was broken off the board - I repaired this. A couple of patch wires had broken off also - I traced where they were supposed to go from my Robocop board, which is a newer revision (My Heavy Barrel topboard is DE-0297-0, it has a couple of places where two tracks have been cut and patch wires installed to reverse the connections. My Robocop's topboard is DE-0297-3, and it has no patch wires; also a couple of minor differences around the 68000 RAM area).

Now the board powered up, but showed only a static pattern of garbage tiles. This indicated that the main CPU (68000) wasn't running. Probing all over the CPU showed that _DTACK (data transfer complete) was locked high, so the 68000 never got past its first memory access cycle. _DTACK is used to allow RAM access arbitration between the CPU and other hardware; the 68000 waits for it to be asserted before going on to the next buss cycle. Injecting 8MHz into _DTACK allowed the board to run "sort of" - the screen was completely corrupted, because of buss contention issues.

Tracing back _DTACK was a pain. Eventually I found it runs back to pin 3 of J14, a 74LS00. Tracing back the inputs to this led back to D16, a 74F30, and further back still, to D12, a 74F139. Pin 2 of this chip runs to a via between D14 and D13. A droplet of something acidic (which smelled like it had come out of a cat) had crept under the solder mask here and eaten through the track just next to the via. A patch wire later, the board was A-OK.

Heavy Barrel uses a vertical low-res monitor, two 8-way rotary joysticks with two buttons, and it has a standard JAMMA pinout. DIP switch settings are as below:

DIP Switch Bank 1

* indicates a factory default setting.

1 2 3 4 5 6 7 8
Coin 1 1 coin 1 credit 0 0
1 coin 2 credits 1 0
1 coin 3 credits 0 1
2 coins 1 credit 1 1
Coin 2 1 coin 1 credit 0 0
1 coin 2 credits 1 0
1 coin 3 credits 0 1
2 coins 1 credit 1 1
Test Mode Play 0
Test 1
Attract mode sound Off 0
On 1
Screen inversion Normal 0
Inverted 1
Reserved Always off 0

DIP Switch Bank 2

* indicates a factory default setting.

1 2 3 4 5 6 7 8
Lives 3 0 0
5 1 0
1 0 1
Infinite 1 1
Difficulty Easy 0 0
Normal 1 0
Advanced 0 1
Expert 1 1
Bonus life 30000, 80000, 160000... 0 0
50000, 120000, 190000... 1 0
100000, 200000, 300000... 0 1
150000, 300000, 450000... 1 1
Continue Off 0
On 1
Reserved Always off 0


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