Frogger cocktail repair log

ELutz

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I always say I'm going to post my repair logs, but I seem to never have time....well here's a start.

Sega Frogger cocktail was droppped off at the shop for repair......Dead!

First I checked the power supply....5VDC line was zero. This machine had the funky Sega set up with a switcher handling the 5VDC and a small linear power supply handling the 12VDC and the -5VDC. This switcher was the tiniest I'd ever seen....and the cabinet was so compact....there wasn't enough room for a regular sized switcher. I decided to try and fix this tiny switcher. I opened it up....replaced some caps, checked the switching transistor, the diodes....all good, but it was still dead. This thing had a couple hybrid "IC's" in it. I figured one of them was the culprit. I dug through my box of "junk" switchers and found the smallest one I had. It was small enough, so I could make it fit. It also only output 5VDC. It checked good, I cappped it, and threw it into the game. Game fires up....but is humming very loud, the screen is jumping around, and it will not coin up. I pull the motherboard and throw it on the bench...it still won't coin up on my bench set up. Looking at the schematics....I see the coin signal goes through a couple resistors, a cap, and ends up at IC7 (an 8255 PIA). I ohm out the resistors with my meter...good. I chech the coin input at the 8255 with a logic probe....it's changing states as I try to coin it up....that's good. So, I figure the output side of tyhe 8255 is bad. I desolder it, and replace it....I can now coin up the game. On my bench, I play a few games.....controls all work.....sound is good. Install board back into the game and start on the monitor. I figured a cap kit would stop thhe vertical jumpiness. The monitor is a Nanao MC-2000S 19". It looks like all original caps. I recap it, vertical issues remain. Damn! I start picking through the vertical deflection circuit.....deflection transistors, the IC, diodes....all looking good. Out of desperation, I swap the deflection transistors anyway......my logic, something has to be failing under load...but testing good otherwise. Transistors are good. I swap the IC...it's good. The vertical deflection circuit has two tantalum caps in it...C404 and C408. I previously checked those with a cap meter....they checked good. I decided to swap them....When I swapped C408.....bingo....stable picture. Bastard! Installed the monitor....everything's good except for the (very) loud hum. It doesn't change with the volume control....it's always there, it's always loud. I figure it's got to be on the small linear regulator board....yep, it was C5 (33000uf25V). All the caps were original, so I replaced them all (but C5 was the guilty one causing the hum). Fixed a broken switch on one of the joysticks......DONE!

Yes, I can be long winded...sorry.
Edward
 
Thanks for posting. It's always good to see these solutions to problems in case someone else has the same symptoms.
 
I agree. Thanks for posting. I enjoy reading logs like this. And on a side note I would totally dig a frogger cocktail!
 
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