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NLG Users Repair Logs and Other Ramblings. Request your very own topic. Just ask any site staff. => Channelmaniac's Arcadecomponents' Old School Repair Logs => Topic started by: channelmaniac on May 04, 2014, 06:54:06 PM
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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.
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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.
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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!
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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.
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Model: In The Hunt
Symptom: Fails self tests
Replaced bad ROM and tested.
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Model: Skins Golf, a.k.a. Major Title 2
Symptom: No audio
Cleaned the board and replaced all the leaking brown Elna caps. Replaced a crumbling, electrolyte damaged resistor pack, and jumpered 2 damaged traces. Tested.
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Model: Skins Golf, a.k.a. Major Title 2
Symptom: Dead, thumping noise and flickering screen.
When the audio amplifier chip thumps like this, it's self-oscillating and drawing large amounts of current in spikes from the power supply. This overloads the switching power supply and causes the +5v to drop out and the screen to flicker.
Removed all the leaking brown Elna capacitors, cleaned the board, and installed all new caps: 7 1uf, 1 47uf, 1 22uf, 1 220uf, 2 100uf, and 1 1000uf electrolytics. Cleaned the edge connector and tested.
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Model: Gunforce
Symptom: Missing backgrounds and sprites
Board had a bad gouge next to a large surface mount custom IC that ran through 13 traces. Removed a bypass filter cap to gain better access to the damaged area. Removed the green conformal coating from the traces with a fiberglass brush then tinned the traces. Using a jeweler's loupe and a 1/16" chisel tip on the soldering iron, tiny 30ga kynar wire patches were laid across the traces. Traces were tested then overcoated with green fingernail polish to protect them. Backgrounds were now fixed, but the sprites were still missing. installed a missing jumper on pins next to the clock oscillator and tested.
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Model: Kung Fu Master
Symptom: Dead
Board had a short on the +12v line causing the power supply to shut down. Replaced 1 shorted tantalum capacitor, 1 missing capacitor, and 3 scraped up capacitors in the audio output circuit. Tested.
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Model: Vigilante
Symptom: Dead
Reworked poorly installed SRAMs at 8A and 8B on the video board. Reflowed the SMT IC at 8C/D to stabilize video display. Replaced bad program ROM and tested.