Raizing "TWIN-CAM" U33

Raizing, original

A GAL16V8B located at position U33 on Mahou Daisakusen, Shippu Mahou Daisakusen, Battle Garegga, and probably Armed Police Batrider. This chip is responsible for generating timing signals for the discrete hardware text plane overlay. Without it, there will be no image.

It can be bypassed at the expense of the text layer by removing the chip, and putting in a jumper between pin 1 and pin 12, which will cause the board to latch the graphics data from the GP9001 custom.

The name "TWIN-CAM" comes from the name printed on the chip on Mahou Daisakusen boards. The name likely alludes to capturing data from two image sources.

The GAL is registered, soldered to the board, and locked, so it can not be trivially dumped. A replacement has been developed and tested in-circuit.

Pins 13-19 are outputs, while pins 1-9, and 12 are inputs. 11 is /OE and is tied to ground, so it may be ignored. Pin 3 is an inverted clock division fed back into the chip for unknown purposes.

Known Vendors

Games Using This Part

Systems Using This Part

Images and Diagrams

TWIN-CAM on a Mahou Daisakusen PCB

TWIN-CAM on a Battle Garegga PCB

The bypass hack, done as a test

Repair Manuals

No manuals currently added.

Repair Tips

Bypass hotfix

The GAL can be bypassed at the expense of the text layer by removing the chip, and putting in a jumper between pin 1 and pin 12, which will cause the board to latch the graphics data from the GP9001 custom. This is a suitable workaround to verify that the board otherwise works.

Failure symptoms

If the game runs, but has a black screen, it is a good sign that U33 may be dead.

If the game won't boot past the initial self test, and/or fails on the Text RAM test, it could be an indication that one or more outputs from this chip has failed. Some outputs control address bus mastery for the text RAM - the CPU must master it when writing to the text RAM, but the readout must master it during active display.

GAL16V8 replacement

A replacement set of equations and compiled JED files are available to allow replacement of U33.

JED file (to burn to a GAL16V8): https://github.com/Mikejmoffitt/bgaregga-gals/raw/master/jed/BG_U33.JED

EQN source file: https://github.com/Mikejmoffitt/bgaregga-gals/blob/master/eqn/BG_U33.EQN