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Ghosts n Goblins Bootleg Repair Log


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I set this PCB up in the test bench this morning started to have a look at the various issues.

 

 

 

 

- Missing the Title Screen

- Lines through characters

- Volume goes in and out randomly

- DIP Switch 1 Bit 1 was broken

- Floating jump wires that had broken off

- Random characters/data permanently on right of the screen.

 

 

The game coins up and plays fine.

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/20170416_095556_zpsfhkumchl.jpg

 

I resoldered the floating wires and DIP1 then started to have a look over the board.

I wanted to have a look at the character issue first.

Starting at the Character Generator ROM, all outputs were firing okay, I then looked at the two 74194s at [10D] and [11D].

Everything looked good there so next was the 74157 at [10C], the inputs were good but there was no output on pins 4 and 7.

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/GnG%2074157_zpsn3yc6z3z.jpg

 

I scrounged a replacement from a parts board and now the Title Screen is back but there is still issues with the lines through the characters.

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/20170416_095840_zpsbtv9uthd.jpg

 

 

 

 

Any suggestions?

Edited by Kaizen
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I don't have a scope so I'm only making 'uneducated' guesses based on what activity I see on the logic probe.

 

Basically it depends on what I'm looking at/for...

 

Eg. Slow alternating pulse, normally high with a brief pulse (or inverse of that), high or low activity when a character is moving on the screen.

Is the gate hi/lo/pulsing, what's happening at the output?

If the pulsing matches a certain action on screen then I can at least see the activity.

 

The 74157 in question had no output showing at all on the logic probe so it was clear to me without a doubt that this chip wasn't outputting.

 

An Oscilloscope is next on the list of test bench tools but I'm getting by okay for now.

Actually seeing what is going on with the data as you know will give a lot more clarity to troubleshooting.

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I think I have two outputs on the ram that are faulty.

I was planning to socket and replace the two of them but I got stuck on another task all day.

I make some time tomorrow to see if that sorts it.

I can throw up some images from the Oscilloscope of what I think are suspect lines, I have only had it for a day and am still learning how to read/use/adjust it.

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I spent a couple of hours on this again this afternoon and made some progress.

 

I went back to the RAM and started to look at the surrounding components.

I discovered that pin 9 on the 74175 at [14H] was floating and pin 12 was stuck low.

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/gng74157x2_zps7fxbs1ht.png

 

I replaced both Fairchild chips at [13H] and [14H], the video improved a bit more...

 

I kept looking around and found pins 12 and 13 on the 7404 at 9D both stuck low.

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/gng%209D%207404_zps6ypjsmye.png

 

I replaced it and there are much less lines missing from the characters...

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/20170418_170038_zpstxgjimu4.jpg

 

http://i1038.photobucket.com/albums/a462/Kaizen088/PCB%20Repair%20Logs/Ghosts%20n%20Goblins%20Bootleg/20170418_201021_zpsd3qiedvq.jpg

 

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  • 1 month later...

I just finished off repairing a GnG today that had quite a few issues. Was actually googling to try and find dip switch settings for a bootleg board (can't get it to continue) and stumbled upon this thread so figured I'd comment.

Your issue will be one or both of the 6148 rams at location 12N and 13N. They are not interchangeable with the 2114.

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Thanks for that. Yes they are the dips for the boot I have but switches are reversed heh. I figured those all out by flicking through them once I got into the test menu. But strangely there's no continue option. Once you die, the continue count down begins and I wasn't able to continue. I figured it out though. You need to hold p1 button whilst pressing start. Not sure why they did it like this.
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  • 3 years later...

I'm back after a bit of a break for most of the year and I finally got this board back on the bench after 3.5 years...

 

I went straight to the RAM at 7N, 8N, 12N AND 13N on the video board, removed and socketed them and swapped out with good RAM for testing.

 

Your issue will be one or both of the 6148 rams at location 12N and 13N. They are not interchangeable with the 2114.

 

 

Two of the four were faulty as suggested by @Holy-SNES, so that fixes the issue of lines through the sprites.

 

I just have the audio issue to sort out now.

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