Aug 062016
 

After Lifeforce, another awesome Konami shoot ’em up on the bench, it’s the turn of Gradius II – GOFER no Yabou :

DSCN3879

DSCN3880

Both CPU and video board were in great shape but this is what I got once powered it up:

DSCN3876

Board sat down on the above message and very rarely showed an ‘ADDRESS ERROR’ or ‘ILLEGAL INSTRUCTION’ message:

DSCN3875

Thanks to my friend Josef who sent me a good Gradius II boardset I could narrow the fault in the CPU board but, before knowing this, during my troubleshooting I found with my logic comparator a couple of faulty Fujitsu TTLs, a 74LS32 @7W on video board and a 74LS157 @8G on CPU board  :

74LS32@7W_reworking

74LS157@8G_reworking

TTL_testing

So I could concentrate exclusively on CPU board since I know the fault was there for sure.Probing the board with my oscilloscope I found some abnormal activity on a couple of 6264 RAM @10E and 10G :

10G_10E_data_bus

Launching the game on MAME I could figure out that these two RAMs are used by both the main and slave 68000 CPU :

selftest

So a failure in them would explain the missing boot.Not being able to determine which chip was actually faulty, I desoldered both and added sockets:

10G_10E_socketed

The one @10G didn’t pass the out-of-circuit test failing in address 1073:

6264@10G_failed

Finally the board could properly boot and enter in game but with missing graphics and crashing after few seconds all the time :

Probing around again with my logic comparator I found a 74LS74 @6F with bad outputs, once removed it failed :

74LS74@6F_removed

74LS74@6F_failed

This fixed the board completely, no other issue were present.Evil Konami defeated again.The battle goes on.

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 Posted by at 10:36 pm

  3 Responses to “Gradius II: Gofer no Yabou repair log #1”

  1. Glad you finally fixed this one ! 🙂

  2. Awesome, always great to read these.