IREM Games

[channelmaniac]

Model: Moon Patrol
Garbage & RAM NG message on the screen

RAM NG is RAM No Good. Error on screen was: RAM NG 8000 55 95

Looked at the schematic. The only RAM location labeled was E000-E7FF for the main program RAM. Checked the wire harnesses between the boards and found that the harness for CN2 on each board had 3 wires cut out. (WHY?) Two of the wires went to nothing. The third went to CN2, pin 17A, which connected to pin 11 of the 74LS157 at location 8L. This was 1/2 of the multiplexed address line A6/H256B signal to address line A6 for the 2114 SRAM ICs  at location 7K and 7L on the character board.

Patched the wire on the harness and tested the board. Reassembled the board stack and replaced 5 broken standoffs.

[channelmaniac]

Model: Moon Patrol
Symptom: Horizontal lines of garbage or solid colors on screen

The video data is written to a set of Intel 2125 SRAM ICs (or equivalent) before being sent out to the monitor. If one of these ICs is bad then you will get thin horizontal lines of junk on the screen.

[channelmaniac]

Tip: IREM board identification

• BBM: Atomic Punk (Bomber Man)
• DB: Dragon Breed
• GF: Gun Force
• LR: Lode Runner
• M72: Gallop - Cosmic Cop
• M90: Atomic Punk (Bomber Man)
• M92: In The Hunt
• MP: Moon Patrol
• MQJ:
• MR: Motorace USA
• MT: Major Title
• MT2: Major Title 2
• YF: 10 Yard Fight
• SNX: Kung-Fu Master
• VG: Vigilante

Thanks to modessitt from the KLOV forums for the info!

[channelmaniac]

Model: Major Title 2 (Irem Skins Golf)
Symptom: Missing foreground graphics

Player and crowd graphics were missing as was the moving bar for shot timing. Straightened the pins at J3 and replaced a bad pin jumper. Fixed a damaged trace going to IC63. Tested.