Troubleshooting Frogger

wpmcnamara

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Donor 2019, 2024
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Work has been crazy busy and its been a long time since my Gyruss boardset rehab, so I decided I should start working on another board. Since I have a Frogger board, and the JAMMA adapter for it, I figured I'd take it off the shelf and see what state it was in.

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I've definitely seen worse. The good news is that it mostly works.

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Here's the starting point:

  • Game program runs, coins up, and starts, detects collision between frog and objects
  • repeated lines in video output
  • responds to control input
  • frog sprite missing
Given it's behavior, I'll be starting with the display generation section. I haven't yet gone searching to see if the answer is readily findable. Will probably do a bit on troubleshooting without help first.
 
I started poking at the board last night. Sure enough, the 8H' signal, feeding the LS157 at IC99, is garbage. So where does it come from? Pin 6 of the LS86 at IC 81. Let's check... oh... well, that's a problem.
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Not entirely sure how I missed that when I was initially looking the board over. :oops2:

This would also explain why the entire background is blue. Two of the gates from that chip are involved in the background color generation. The final gates a signal to object data ROM. I'd venture that its why the frog is missing.
 
I started poking at the board last night. Sure enough, the 8H' signal, feeding the LS157 at IC99, is garbage. So where does it come from? Pin 6 of the LS86 at IC 81. Let's check... oh... well, that's a problem.

LOL.
It's missing on the back side too:

On the sprites that should only relate to byte swapping for flip, so it's not likely the only cause if you're not getting any sprites.

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Other than dealing with a clogged tip on my Hakko and some gunk on the board the charred under heat, that was an easy fix.

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Fixed the background, the double half lines, and the missing frog. So all the game play is there. Just no sound. So next up will be probing the sound board.
 
Fixed the background, the double half lines, and the missing frog. So all the game play is there. Just no sound. So next up will be probing the sound board.

You don't seem to have a sound pot hooked up to the 6 pin header on the sound board.

Use your finger to short across the whole header (~1/2 resistor divider) and see if you get sound back.
 
Yes, adding the sound pot fixed the sound.

This turned into a rather "un interesting" repair. 🤷‍♂️

Still need to clean the boards, replace the electrolytic caps, probably replace some ceramics as well, and clean up the "fix" on the bottom of the board. Fundamentally it works though. A couple of the 74201 static rams run noticeably warmer than the rest but I probably won't both those at the moment.

The Frogger schematics are also atrocious.
 
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