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Sega Moonwalker Repair Log


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A nice quick fix for a Saturday arvo.

 

One of the few games I really love despite having no nostalgia factor for is Moonwalker (I'd never even heard of it until I got into Arcade gear about ten years ago) so I can never resist picking them up when the pop up for sale as faulty, even if I have mint keeper PCB in the collection already.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6145.jpg

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6146.jpg

 

It was sold as having absolutely no sound and a sprite problem, in that MJ would just crouch and freeze when hit, or crouch and drift slowly around the screen bouncing off walls. The enemies lose interest in him when he is stuck in this state and the game just runs on forever with MJ neither dead or alive.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6152.jpg

 

I've fixed a couple of these boards before and one unusual feature is that the Sega System 18 sound section controls the audio as well as some sprite animation, I don't know if it does in other System 18 games or just this one. The result is that what would look like two totally separate faults on any other board, was probably only a single issue.

 

The PCB was in very good condition, only one missing decoupling capacitor...

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6147.jpg

 

...and had been upgraded with bathroom sealant to hold ROM board on - why use PCB standoffs and bolts when you can silicone the damn thing together? Thanks random Arcade Operator!

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6148.jpg

 

A quick eyeball over the board gave the first clue...

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6149.jpg

 

... a ball of what looks like dust and fluff, but is actually an old insect nest, considering it was well stuck down and right next to the Z80 that runs the audio section, the main suspect was track damage somewhere nearby. With the ROM board peeled off there were more signs of insect habitation, and probably an leg from the long gone culprit.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6158.jpg

 

The two nesty areas cleaned up pretty nicely with barely a mark on the PCB underneath, but clearly most of the action had been happening over here, right next to the TMM2063 SRAM chip that is part of the audio section.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6161.jpg

 

Under magnification the track to pin 2 looks suspect, and the track and via connecting to pin 3 looks completely rotten. In fact the connection to pin 3 was still there, but the track to pin 2 was broken.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6162.jpg

 

With a working System 18 PCB handy it was easy to check were pin 2 should connect to - pin B18 on the CN3 connector to the ROM board, so one small length of hookup wire later...

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6163.jpg

 

... the problem was fixed! Sound restored and sprites were behaving again.

 

I actually fitted another link to bypass the really dodgy looking track to pin 3 as I doubt there is much copper left in that path.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6166.jpg

 

I also scavenged an exact replacement 470uF 16V capacitor from a scrap System 16 PCB to replace the missing one, and keep them all matching.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6165.jpg

 

MJ can dance once more, and I feel better about buying more stuff while simultaneously trying to downsize.

 

http://i40.photobucket.com/albums/e230/Womble76/Moonwalker/IMG_6170.jpg

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