PCB Repair Logs Moon Patrol

Moon Patrol

Moon Patrol

Manufacturer	Irem
Year	1982
PCB Image	Reserved
Pin Out	Moon Patrol

Repairer: Arcade King
Forum Thread: Moon Patrol PCB Repair

Can't believe I haven't put this up. Wish I had a dollar for every Moon Patrol set I've worked on over the years. Some of these Logs go back to 2005 and really only wrote them down for my own reference so pretty straight to the point. Most recent one was yesterday. Pulled my boards out to fit the high score/ freeplay mod and of course they both had issues.

General Tips. Make sure all inter connecting cables are firmly in. Always good to have a working set so you can swap layers to identify the problem layer. 95% of issues on the boards below were from F(Fujitsu) branded logic chips. No point going into detail as to why they fail, I've been documenting the failure of these IC's for well over 7 years now. Usually when a Fujitsu IC fails its just goes dead and is easy to isolate so a real no brainier.. A lot of these IC's are well over 30 years old now so its amazing that they are still working at all.

Tools used. Logic Probe CRO Desoldering station. Patience!

Board MP-712A

This is the Sound Board
Problem: no sound at all.
Fix: The cpu and two 8910 sound chips were all bad replacing them fixed the board.
Update: after the board was fixed it has been going into meltdown mode. After a few hours the sound decided to die.

I started by replacing all the caps which ddint fix the problem however fixed the crackle and amp from getting too hot. However when the board was cold the sound would run for 10-20 seconds then crackle out. The problem was a 74LS138@1E

Problem: No explosion noise.
Fix: Green cap @ C37 104k leg was broken.

Board MP-712C
This is the character board, buggy aliens ships etc. This board had so many faults it wasn't funny, just as you thought I had fixed it another problem would surface. I can only nail this down to how old the board is and how badly a lot of the ICs were corroded.

I wont be able to list all the problems as there were too many. The board was completely dead as the CPU and Sound boards were. Looking at the the board there were a few chips that had no markings on them obviously damaged from heat. I also noticed the board was shorted from +5 to neg so basically it was a matter of finding the bad chips. I started replacing all the chips that marking were burnt off.

Board Mp-712D
This board controls the background graphics and scoreboard.

The board was dead as the same as the rest, first inspection indicates 4 chips fried at the top with labels burnt off which follows. 74LS32@B2 74LS86@A5 74LS32@A6 74LS74@A7 The colour prom at A2 legs were rusted and broke off so I had to get a replacement.

Ok now the board fired up but background was messed up and sometimes blacked out, no scoreboard and no ground. 74LS157@L2 fixed the background and 74LS157@E2 fixed the scoreboard and ground. Ok now we have all the back and foreground back a new problem arises. Background flashing badly. 74LS86@L6 Flashing has stopped hover one problem remains. the furtherest scrolling background is jittering like some sort of memory loop.
Fixed: 74LS175@M5

Board is now fixed.

Notes:
This board has in fact the Moon Ranger roms on it. When I was fixing the boards the Moon Ranger looked messed up and spelt out Moon Rangor. It is the same for every screen shot I have seen on the net. Found out by accident when I was working on the bottom board that Moon Ranger requires a different rom No.11 on the bottom board. when you mixed moon ranger roms on the bottom and moon patrol the T is messed up in patrol. I assumed this was a bad rom but after fixing all boards this clears up the Ranger .

ON, the 2532 I need burnt is 1e from the 4in1fun set from mame.

update: 3/12/05
Board ran for about 3 hours today before going into self destruct mode again. Screen now is full of "M"s the buggy also fires M's upwards. The problem goes away when you turn the voltage right down.

I went through all the boards connecting my good set up to each one... the bottom board sigh.

Took me ages to work this one out aggges. I swapped out a few other chips I suspected A 74ls166@2D and a 02@1f with no luck mind you I have no regrets swapping these chips as a lot of them on this board are badly corroded and are bound to fail as they have been.

My attention turned to the 74ls374@4D going through the pins with the logic probe i noticed pin 3 was erratic i tried shorting pin 3 and 4 together and it cleared up the screen. Instead of actually checking the datasheet to see if it was a input or output i proceeded to replace the 374. surprise surprise no change...in fact it was worse because when you turned down the voltage the problem doesn't go away at all now.

Pin 3 of the 374 a input was also sitting high now doing nothing, I traced it back to a 74LS365@5d a 6-bit 3-state non inverting buffer/line driver which is right next to it pin 9. **** I don't have any of these, I tried a similar chip a 367 2/4-bit 3-state non inverting buffer/line driver. which cleared up the problem. Almost the same chip..almost.
Fix: 74LS365@5D

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